Efficient and reliable acknowledgement process for new radio operation in unlicensed bands

Abstract

Systems, methods, and devices for efficient and reliable handling of acknowledgements in a new radio unlicensed band (NR-U) environment. A wireless transmit receive unit (WTRU) may receive control information and data transmission from a gNB in a first interval (i.e., transport block or channel occupancy time), wherein the control information may include an indication of uplink resources. The data transmission may require a certain acknowledgement (i.e., HARQ feedback). The WTRU may attempt to transmit the acknowledgement in the indicated uplink resource, but the gNB may not receive the acknowledgement. The WTRU may receive control information and data transmissions from the gNB in a second interval, including indications for aggregating any previously unsuccessful acknowledgement transmissions. The WTRU may transmit an aggregated acknowledgement from the current interval, including a previously unsuccessful acknowledgement and any other acknowledgement. In some cases, a look-before-talk (look-before-talk) process may be used, in some embodiments, for example.

Description

[0001] This application is a divisional application of the invention patent application with application number 201980053260.6 filed on August 8, 2019 and invention name “Effective and reliable response process for new radio operations in unlicensed bands”.

[0002] Claiming priority

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 716,211, filed on August 8, 2018, and U.S. Provisional Application No. 62 / 753,457, filed on October 31, 2018, the contents of which are incorporated herein by reference. Background Art

[0004] In the field of wireless communications, next generation air interfaces such as new radio may support a wide range of use cases with different spectrum usage models, such as licensed, unlicensed / shared, etc. In order to operate in shared spectrum, systems, methods, and devices that enable efficient and reliable wireless communications in unlicensed bands may be needed. Summary of the invention

[0005] Systems, methods and apparatus for efficient and reliable handling of acknowledgments in a new radio unlicensed band (NR-U) environment. A wireless transmit receive unit (WTRU) may receive control information and a data transmission from a gNB in ​​a first interval (i.e., a transport block or channel occupancy time), wherein the control information may include an indication of uplink resources. The data transmission may require some kind of acknowledgment (i.e., HARQ feedback). The WTRU may attempt to transmit the acknowledgment in the indicated uplink resources, but the gNB may not receive the acknowledgment. The WTRU may receive control information and a data transmission from the gNB in ​​a second interval, including an indication for aggregating any previously unsuccessful acknowledgment transmissions. The WTRU may transmit an aggregated acknowledgment from the current interval, the aggregated acknowledgment including the previously unsuccessful acknowledgment and any other acknowledgments. In some cases, a look-before-talk procedure may be used. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0007] Figure 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented;

[0008] Figure 1B It is shown that according to the embodiment, Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use in a communication system is shown;

[0009] Figure 1C It is shown that according to the embodiment, Figure 1A A system diagram of an example radio access network (RAN) and an example core network (CN) used in the communication system shown;

[0010] Figure 1D It is shown that according to the embodiment, Figure 1A A system diagram of another example radio access network (RAN) and another example core network (CN) used in the communication system shown;

[0011] Figure 2 is an example transmission diagram where the WTRU fails to complete the LBT procedure;

[0012] Figure 3 is an example transmission diagram where the WTRU fails to complete the LBT procedure;

[0013] Figure 4 is an example transmission diagram where the WTRU has priority for non-exclusive PUCCH;

[0014] Figure 5 is an example transmission diagram where the WTRU successfully completes LBT but the gNB fails to detect PUCCH;

[0015] Figure 6 is an example transmission diagram in which a WTRU prepares a HARQ codebook based on at least a DAI and / or an EDAI;

[0016] Figure 7 is an example transmission diagram in which a WTRU prepares a HARQ codebook based on at least a DAI and / or an EDAI;

[0017] Figure 8 is an example transmission diagram of a WTRU based on an EDAI aggregated HARQ codebook for one or more COTs;

[0018] Fig. 9 is an example transmission diagram where PUCCH resources are assigned outside the COT and PUCCH from a later COT is used;

[0019] Fig.10 is an example transmission diagram where the WTRU examines the properties of the scheduled PUCCH to determine gapless transmission;

[0020] Fig.11 is an example procedure for contention window adjustment;

[0021] Fig.12 is an example transmission diagram for basic COT sharing; and

[0022] Fig.13 is an example transmission graph of COT sharing with limited hidden node influence. DETAILED DESCRIPTION

[0023] Figure 1A 1 is a diagram showing an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. 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 by sharing system resources including wireless bandwidth. For example, the communication system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail unique word DFT spread OFDM (ZT UW DTS-sOFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and 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, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, Internet 110, and other networks 112, although it should be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network components. Each WTRU 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, any of the WTRUs 102a, 102b, 102c, 102d may be referred to as a “station” and / or “STA”, which may be configured to transmit and / or receive wireless signals, and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular 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 working in an industrial and / or automated process chain environment), consumer electronic devices, and devices working on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, 102d may be interchangeably referred to as WTRU / UE.

[0025] The communication system 100 may also include a base station 114a and / or a base station 114b. Each base station 114a, 114b may be any type of device configured to facilitate access to one or more communication networks (e.g., CN 106 / 115, Internet 110, and / or other networks 112) by wirelessly interfacing with at least one of the WTRUs 102a, 102b, 102c, 102d. For example, the base stations 114a, 114b may be base transceiver stations (BTS), Node Bs, eNode Bs, Home Node Bs, Home eNode Bs, gNBs, NR Node Bs, site controllers, access points (APs), and wireless routers, among others. Although each base station 114a, 114b is depicted as a single component, it should be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network components.

[0026] The base station 114a may be part of the RAN 104 / 113, and the RAN 104 / 113 may also include other base stations and / or network components (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, and the like. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies called cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a specific geographic area that is relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, that is, each transceiver corresponds to a sector of the cell. In one embodiment, the base station 114a may use multiple-input multiple-output (MIMO) technology and may use multiple transceivers for each sector of the cell. For example, by using beamforming, signals may be transmitted and / or received 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 described above, the communication system 100 may be a multiple access system and may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA, among others. 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 (DL) Packet Access (HSDPA) and / or High Speed ​​UL 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), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-APro).

[0030] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as new radio (NR) radio access, which may establish the air interface 116 using NR.

[0031] 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 jointly implement LTE radio access and NR radio access (e.g., using dual connectivity (DC) principles). Thus, the air interface used by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0032] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE), and GSM EDGE (GERAN), among others.

[0033] Figure 1A The base station 114b in the example may be a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may use any appropriate RAT to facilitate wireless connectivity in a local area, such as a business location, a residence, 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 establish a wireless local area network (WLAN) by implementing a radio technology such as IEEE 802.11. In one embodiment, the base station 114b and the WTRUs 102c, 102d may establish a wireless personal area network (WPAN) by implementing a radio technology such as IEEE 802.15. In another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell by using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, and the like). Figure 1A As shown, the base station 114b may be directly connected to the Internet 110. Thus, the base station 114b does not need to access the Internet 110 via the CN 106 / 115.

[0034] 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, fault 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 may perform advanced security functions such as user authentication. Although in Figure 1AAlthough not shown, 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 or a different RAT as the RAN 104 / 113. For example, in addition to being connected to the RAN 104 / 113 employing NR radio technology, the CN 106 / 115 may also be in communication with other RANs (not shown) employing GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0035] 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 network devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet Protocol Suite. The networks 112 may include wired and / or wireless 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 use the same RAT or a different RAT as the RAN 104 / 113.

[0036] 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 over 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.

[0037] Figure 1B is a system diagram showing an example WTRU 102. Figure 1B As shown, the WTRU 102 may include a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keyboard 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 should be appreciated that the WTRU 102 may include any sub-combination of the foregoing components while remaining consistent with an embodiment.

[0038] 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, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, however it should be appreciated that the processor 118 and the transceiver 120 may also be integrated into one electronic component or chip.

[0039] The transmit / receive component 122 may be configured to transmit or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive component 122 may be an antenna configured to transmit and / or receive RF signals. As an example, in another embodiment, the transmit / receive component 122 may be a transmitter / detector configured to transmit and / or receive IR, UV, or visible light signals. In yet another embodiment, the transmit / receive component 122 may be configured to transmit and / or receive RF and light signals. It should be appreciated that the transmit / receive component 122 may be configured to transmit and / or receive any combination of wireless signals.

[0040] Although in Figure 1B 102 as a single component, but the WTRU 102 may include any number of transmit / receive components 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive components 122 (e.g., multiple antennas) for transmitting and receiving radio signals over the air interface 116.

[0041] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive component 122 and to demodulate signals received by the transmit / receive component 122. As described above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers that allow the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0042] The processor 118 of the WTRU 102 may be coupled to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit), and may receive user input data from these components. The processor 118 may also output user data to the speaker / microphone 124, the keyboard 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any 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 memories that are not physically located in the WTRU 102, such as, for example, a server or a home computer (not shown).

[0043] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power for use by 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 (Ni-Cd), nickel-zinc (Ni-Zn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0044] 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) related to 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) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be appreciated that the WTRU 102 may acquire location information via any suitable positioning method while remaining consistent with an embodiment.

[0045] The processor 118 may also be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Modules, frequency modulation (FM) radio units, digital music players, media players, video game console modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, and activity trackers, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors, geolocation sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, and / or humidity sensors.

[0046] The WTRU 102 may include a full-duplex radio for which reception or transmission 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. A full-duplex radio may include an interference management unit 139 that reduces and / or substantially eliminates self-interference by means of hardware (e.g., chokes) or by signal processing by a processor (e.g., a separate processor (not shown) or by the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for transmitting and receiving some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)).

[0047] Figure 1C 1 is a system diagram showing the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may communicate with the WTRUs 102a, 102b, 102c using an E-UTRA radio technology over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0048] The RAN 104 may include eNode-Bs 160a, 160b, 160c, however it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. Each of the eNode-Bs 160a, 160b, 160c may include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, for example, the eNode-B 160a may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0049] Each eNodeB 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0050] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. Although each of the foregoing components are described as being part of the CN 106, it should be appreciated that any of these components may be owned and / or operated by an entity other than the CN operator.

[0051] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 142 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, performing bearer activation / deactivation processing, and selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c. 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 and / or WCDMA.

[0052] The SGW 164 may be connected to each of the eNode-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-eNode-B handovers, triggering paging processing when DL data is available for the WTRUs 102a, 102b, 102c, and managing and storing the contexts of the WTRUs 102a, 102b, 102c, and the like.

[0053] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0054] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or communicate with, an IP gateway, such as an IP Multimedia Subsystem (IMS) server, that may act as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0055] Although in Figures 1A-1D The WTRU is described as a wireless terminal, however it should be appreciated that in certain typical embodiments, such a terminal may (eg, temporarily or permanently) use a wired communication interface with a communication network.

[0056] In a typical embodiment, the other network 112 may be a WLAN.

[0057] A WLAN using an infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may access or be connected to a distributed system (DS) or other types of wired / wireless networks that send traffic into and / or out of the BSS. Traffic originating from outside the BSS and destined for the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, for example, the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. The point-to-point traffic may be sent using a direct link establishment (DLS) between the source and destination STAs (e.g., directly therebetween). In certain typical embodiments, the DLS may use 802.11e DLS or 802.11z channelized DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. Here, the IBSS communication mode may sometimes be referred to as an "ad hoc" communication mode.

[0058] When using the 802.11ac infrastructure mode of operation or a similar mode of operation, the AP may transmit a beacon on a fixed channel (e.g., a primary channel). The primary channel may have a fixed width (e.g., a bandwidth of 20 MHz) or a width that is dynamically set with the aid of signaling. The primary channel may be a working channel of the BSS and may be used by STAs to establish a connection with the AP. In certain typical embodiments, carrier sense multiple access (CSMA / CA) with collision avoidance (e.g., in an 802.11 system) may be implemented. For CSMA / CA, STAs (e.g., each STA) including the AP may sense the primary channel. If a particular STA senses / detects and / or determines that the primary channel is busy, the particular STA may back off. In a specified BSS, one STA (e.g., only one station) may transmit at any given time.

[0059] A high throughput (HT) STA may communicate using a 40 MHz wide channel (eg, by combining a 20 MHz wide primary channel with a 20 MHz wide adjacent or non-adjacent channel to form a 40 MHz wide channel).

[0060] Very high throughput (VHT) STA can support channels with widths of 20MHz, 40MHz, 80MHz and / or 160MHz. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels or by combining two discontinuous 80MHz channels (this combination can be referred to as an 80+80 configuration). For the 80+80 configuration, after channel coding, the data can be transmitted and passed through a segment parser, which can separate the data into two streams. Inverse fast Fourier transform (IFFT) processing and time domain processing can be performed separately on each stream. The stream can be mapped on two 80MHz channels, and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0061] 802.11af and 802.11ah support sub-1 GHz operating modes. Compared with 802.11n and 802.11ac, the channel operating bandwidth and carrier used in 802.11af and 802.11ah are reduced. 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 typical embodiments, 802.11ah can support meter type control / machine type communication (e.g., MTC devices in macro coverage areas). MTC can have certain capabilities, such as limited capabilities including support (e.g., only support) certain and / or limited bandwidths. MTC devices can include a battery, and the battery life of the battery is higher than a threshold (e.g., for maintaining a very long battery life).

[0062] For WLAN systems that can support multiple channels and channel bandwidths (e.g., 802.11n, 802.11ac, 802.11af, and 802.11ah), the WLAN system includes a channel that can be designated as a primary channel. The bandwidth of the primary channel can be equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel can be set and / or limited by a certain STA, where the STA originates from all STAs operating in the BSS that supports the minimum bandwidth operating mode. In the example of 802.11ah, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz and / or other channel bandwidth operating modes, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the width of the primary channel can be 1MHz. Carrier sensing and / or network allocation vector (NAV) settings can depend on the status of the primary channel. If the primary channel is busy (e.g., because a STA (which only supports the 1MHz operating mode) transmits to the AP), then even if most of the frequency band remains space and is available for use, the entire available frequency band can be considered busy.

[0063] 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. Depending on the country code, the total bandwidth available for 802.11ah is 6MHz to 26MHz.

[0064] Figure 1D 1 is a system diagram showing the RAN 113 and the CN 115 according to one embodiment. As described above, the RAN 113 may communicate with the WTRUs 102a, 102b, 102c using NR radio technology over the air interface 116. The RAN 113 may also communicate with the CN 115.

[0065] 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 the embodiments. Each of the gNBs 180a, 180b, 180c may include one or more transceivers to communicate 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 use beamforming processing to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, for example, the gNB 180a may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, gNB 180a may transmit multiple component carriers (not shown) to WTRU 102a. 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, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0066] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter configurations (numerology). For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may be different for different transmissions, different cells, and / or different portions of the radio transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of different or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths).

[0067] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing other RANs (e.g., 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 WTRU 102a, 102b, 102c may communicate / connect to the gNB 180a, 180b, 180c while communicating / connecting to another RAN (e.g., the eNode-B 160a, 160b, 160c). For example, the WTRU 102a, 102b, 102c may communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c in a substantially simultaneous manner by implementing the DC principle. In a non-standalone configuration, the eNode-B 160a, 160b, 160c may act as a mobility anchor for the WTRU 102a, 102b, 102c, and the gNB 180a, 180b, 180c may provide additional coverage and / or throughput to serve the WTRU 102a, 102b, 102c.

[0068] Each gNB 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support network slicing, implement dual connectivity, implement interworking between NR and E-UTRA, route user plane data to user plane functions (UPFs) 184a, 184b, and route control plane information to access and mobility management functions (AMFs) 182a, 182b, and the like. Figure 1D As shown, gNBs 180a, 180b, and 180c can communicate with each other through the Xn interface.

[0069] Figure 1DThe CN 115 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and may include a data network (DN) 185a, 185b. Although each of the aforementioned components is described as part of the CN 115, it should be understood that any of these components may be owned and / or operated by entities other than the CN operator.

[0070] 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 WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting a specific SMF 183a, 183b, managing registration areas, terminating NAS signaling, and mobility management, etc. The AMF 182a, 1823b may use network slicing processing to customize the CN support provided to the WTRUs 102a, 102b, 102c based on the type of service used by the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, and / or services for machine type communication (MTC) access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 and other RANs (not shown) using other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0071] 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 may configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating WTRU IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0072] The UPF 184a, 184b can be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which can provide the WTRUs 102a, 102b, 102c with access to packet-switched networks (e.g., the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b can perform other functions such as routing and forwarding packets, implementing user plane policies, supporting multi-host PDU sessions, processing user plane QoS, buffering downlink packets, and providing mobility anchoring, etc.

[0073] 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 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 an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b, and through the UPFs 184a, 184b.

[0074] In view of Figures 1A-1D and about Figures 1A-1D , one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU 102a-d, base station 114a-b, eNodeB 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein. These simulation devices may be one or more devices configured to simulate one or more or all of the functions herein. For example, these simulation devices may be used to test other devices and / or simulate network and / or WTRU functions.

[0075] The simulation device can be designed to implement one or more tests about other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being implemented and / or deployed as part of a wired and / or wireless communication network in whole or in part to test other devices inside the communication network. The one or more simulation devices can perform one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to other devices to perform the test, and / or can use over-the-air wireless communication to perform the test.

[0076] The one or more simulation devices can perform one or more functions, including all functions, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test lab and / or a test scenario of a wired and / or wireless communication network that is not deployed (e.g., tested) to implement tests on one or more components. The one or more simulation devices can be test devices. The simulation device can transmit and / or receive data using direct RF coupling and / or wireless communication with the aid of RF circuits (which can include one or more antennas, for example).

[0077] In wireless systems, such as those described herein, Figures 1A-1D In a wireless system, a central node (e.g., a gNB) may serve a group of WTRUs, and one or more opportunities for sending transport blocks (TBs) from the WTRUs to the central node may be managed by the central node. For example, the gNB may schedule uplink (UL) transmissions of the respective WTRUs by assigning separate time-frequency resources to each WTRU and granting each resource to one WTRU. This arrangement for UL transmissions is sometimes referred to as grant-based UL transmissions. Alternatively, the gNB may announce the presence of one or more time-frequency resources and allow a group of WTRUs to use each resource, thereby allowing access without a specific UL grant.

[0078] In some cases, unlicensed bands may be used exclusively or partially in a wireless system, where a base station (e.g., gNB) or WTRU needs to perform listen before talk (LBT) before accessing an unlicensed wireless channel to ensure fair channel access. Depending on the regulatory requirements for the unlicensed channel, the LBT specifications may be different. In general, the LBT process may include fixed and / or random duration time intervals, where a wireless node (e.g., gNB or WTRU) listens to the medium, and if the energy level detected from the medium is above a threshold (specified by the regulator) the gNB or WTRU refrains from transmitting any wireless signal; otherwise the wireless node may transmit its desired signal after the duration (i.e., the LBT process is completed). The LBT duration time interval is the time spent detecting / sensing before transmission, which means that a longer LBT duration time interval means a longer wait time for transmission.

[0079] In general, NR technology can be applied to many use cases such as ultra-reliable low-latency communication (URLLC), massive machine type communication (mMTC or MMTC), or enhanced mobile broadband (eMBB or EMBB) communication. MMTC can enable low-cost, large-volume, battery-powered communication between devices designed to support applications such as smart metering, logistics, and field and body sensors. URLLC can enable ultra-reliable, very low latency, and high-availability communication between devices and machines for applications such as vehicle communication, industrial control, factory automation, remote surgery, smart grid, and public safety applications. EMBB can address enhancement issues in multiple parameters such as data rate, latency, and mobile broadband access coverage. To meet the performance requirements of these use cases, NR can have specific parameters and capabilities.

[0080] NR may specify various parameter configurations with subcarrier spacing ranging from 15KHz to 240KHz. The base subcarrier spacing may be 15KHz and other parameter configurations may have increased subcarrier spacing, which is a power of 2 multiplied by the base subcarrier spacing, as listed in Table 1 below.

[0081]

[0082] Table 1: NR parameter configuration

[0083] The physical downlink control channel (PDCCH) in NR can consist of one or more control channel elements (CCEs), up to 16 CCEs depending on the aggregation level. The control resource set (CORESET) can consist of resource blocks, given by the higher layer parameter CORESET-freq-dom, and in the time domain symbols, given by the higher layer parameter CORESET-time-dur. Some relevant parameters given to the PDCCH may be: Group Common (GC) PDCCH, configured by RRC; Common PDCCH, system information and paging for all WTRUs; Residual System Information (RMSI), configured by PBCH; Other System Information (OSI), configured by PBCH.

[0084] The Physical Uplink Control Channel (PUCCH) in NR can support multiple formats, as shown in Table 2.

[0085] PUCCH format OFDM symbol length Number of bits 0 1–2 ≤2 1 4–14 ≤2 2 1–2 >2 3 4–14 >2 4 4–14 >2

[0086] Table 2: PUCCH format

[0087] In a NR frame, an OFDM symbol in a slot can be classified as 'downlink' (marked as 'D'), 'flexible' (marked as 'X'), or 'uplink' (marked as 'U'). Table 3 shows the structure.

[0088]

[0089] Table 3: Various formats of NR time slots

[0090] In some regulatory regimes, a Listen Before Talk (LBT) procedure is mandatory for unlicensed channel usage and thus there may be LBT categories for protocols such as License Assisted Access (LAA), enhanced LAA (eLAA), and further eLAA (feLAA). The LBT Category 4 (CAT 4) scheme adopted in LAA / eLAA may be the preferred scheme for some use cases. When the eNB or gNB and in some cases the WTRU wants to transmit control or data in an unlicensed channel, the LBT CAT 4 procedure may begin. The device may then perform an initial Clear Channel Assessment (CCA) where the channel is checked to be idle for a period of time (i.e., the period is the sum of a fixed period and a pseudo-random duration). Channel availability is then determined by comparing the energy detected (ED) level across the bandwidth of the unlicensed channel to an energy threshold determined by the regulator.

[0091] If the channel is determined to be idle, transmission can be made. If it is not idle, the device performs a slotted random backoff process where a random number can be selected from a specified interval called a contention window. A backoff countdown can be obtained and the channel is verified to be idle, and a transmission can be initiated when the backoff counter reaches zero. After the eNB or gNB has gained access to the channel, it may be allowed to transmit for a duration called the channel occupancy time (COT), but only for a limited duration called the maximum channel occupancy time (MCOT). The CAT 4 LBT process with random backoff and variable contention window size can achieve fair channel access and good coexistence with other radio access technologies (RATs) such as Wi-Fi and other LAA networks. The following are examples of LBT categories: Category 1 no listening interval; Category 2 fixed duration listening interval (e.g., 25μs); Category 3 random duration listening interval with fixed contention window; and Category 4 random duration listening interval with increased contention window.

[0092] In Category 3 LBT, the transmitter may extract a random number N within a contention window. The size of the contention window may be specified by a minimum and maximum value of N. The size of the contention window may be fixed. During the LBT process, the random number N may be used to determine the duration for which a channel is sensed to be idle before a transport entity transmits on the channel.

[0093] In Category 4 LBT, the transmitter may extract a random number N within a contention window. The size of the contention window may be specified by the minimum and maximum values ​​of N. The transmitting entity may change the size of the contention window when extracting the random number N. During the LBT process, the random number N may be used to determine the duration for which a channel is sensed as idle before the transmitting entity transmits on the channel.

[0094] As described herein, a carrier bandwidth part (BWP) may be a contiguous set of physical resource blocks selected from a contiguous subset of common resource blocks configured for a given parameter on a given carrier.

[0095] The WTRU may be configured with up to four carrier BWPs in the downlink, with a single downlink carrier BWP being active at a given time. The WTRU may not be expected to receive PDSCH, PDCCH, CSI-RS or TRS outside of the active BWP. The WTRU may be configured with up to four carrier BWPs in the uplink, with a single uplink carrier BWP being active at a given time. If the WTRU is configured with a supplementary uplink, the WTRU may also be configured with up to four carrier BWPs in the supplementary uplink, with a single supplementary uplink carrier BWP being active at a given time. The WTRU may not transmit PUSCH or PUCCH outside of the active BWP.

[0096] For HARQ operation in NR, a 3-bit PDSCH to HARQ timing indicator field may indicate flexible HARQ feedback timing. There may be a one-to-one mapping between the PDSCH and the corresponding feedback on the PUCCH / UCI. The slot timing between the PDSCH and the PUCCH (referred to as K1) may be indicated in a 3-bit field in the DCI, indexing eight RRC configured values. In DCI format 1-1, these eight values ​​may be mapped to RRC configured delay values ​​(i.e., the mapping is {000,…,111}->RRC defined values). In DCI format 1-0, these eight values ​​are mapped to delay sets {1,2,…,8}.

[0097] NR can support a small processing delay, but no less than providing feedback in the same timeslot (e.g., for capability 1 WTRU). For example, for a subcarrier spacing of 30KHz, the minimum L1 processing delay from the end of the PDSCH to the beginning of the PUCCH can be 10 OFDM symbols. N1 can be the number of OFDM symbols from the end of the PDSCH to the beginning of the PUCCH. Frontload DMRS can be only 10 and 17 symbols for SCS=30kHz and 60kHz, and frontload + additional DMRS can be 13 and 20 symbols for SCS=30kHz and 60kHz. N2 can be the number of OFDM symbols from the end of the PDCCH (i.e., UL grant) to the beginning of the PUSCH. Frequency-first RE mapping (Freq.-first RE-mapping) can be 12 and 23 symbols for SCS=30kHz and 60kHz.

[0098] NR may support dynamic indication of PUCCH resources and time, and HARQ feedback for multiple PDSCHs may be sent using a single HARQ codebook. The PUCCH resources and time may be indicated in the scheduling DCI in case of dynamically scheduled transmissions. The association between PDSCH and PUCCH may be based on the PUCCH resources and time indicated in the scheduling DCI; the HARQ feedback for all PDSCHs for which the scheduling DCI indicates the same PUCCH resources and time may be reported together. The most recent PDSCH feedback that can be included may be limited by the processing time required for the WTRU to prepare the HARQ feedback.

[0099] NR can use semi-static or dynamic codebooks to aggregate feedback from multiple HARQ processes in one PUCCH.

[0100] For semi-static NR feedback aggregation, the ACK codebook size can be determined based on the maximum number of TBs across PDCCH monitoring opportunities and cells that can be configured for ACK on the same timeslot. This mode is more reliable than the dynamic mode for lost and erroneous DCI detection, but at the expense of more bits required for ACK feedback. For example, using 8 CBGs and 16 HARQ processes, 128 bits per cell are transmitted to a single HARQ feedback, even for a single TB.

[0101] For dynamic NR feedback aggregation, the set of HARQ processes may be dynamically determined for each HARQ process for which feedback should be reported. In general, the HARQ codebook size may be determined based on the content of multiple consecutively received DCIs, based on which the gNB efficiently communicates the codebook properties to the WTRU. The downlink assignment indicator (DAI, 2 bits) may indicate the number of HARQ processes that should be reported; the DAI may make it robust to lost / erroneous DCIs. To index the HARQ codebook, each DCI for a scheduling assignment may contain a DAI that counts all previous DL assignments including the current assignment, which may be included in the HARQ codebook. The DAI contained in the DCI of the most recent DL assignment may determine the HARQ codebook size. Even if the WTRU loses some DL assignments, it may still correctly address the HARQ codebook as long as the DAI does not wraparound. The DAI in the DL scheduling DCI is stepped by 1 compared to the immediately preceding DL scheduling DCI; if the difference is greater than 1, it may indicate that the PDCCH has been lost.

[0102] There may be one or more HARQ process(es) for grant-free UL transmissions in NR. Grant-free (GF) UL transmissions (also called configured grants) and associated HARQ processes may have several types and attributes in NR. Type I may be via RRC configuration only, where the WTRU is configured to access GF resources. Type II may be with RRC configuration and DCI signaling, where the WTRU is configured to access GF resources, and access to GF resources is activated, deactivated, or reactivated using DCI signaling. GF UL transmissions may be configured to occur on a slot basis or on a mini-slot basis.

[0103] One attribute of the HARQ process may be acknowledgment, HARQ feedback, and retransmission as follows: grant-based TB retransmission after GF transmission failure; and grant-free TB transmission up to K=8 repetitions across consecutive GF resources with early termination if the WTRU receives an implicit acknowledgment indication.

[0104] The implicit HARQ attribute may be that there is no explicit HARQ-ACK feedback, and it may be implicit by using the NDI field in the DCI format that explicitly indicates the UL HARQ process ID. In addition, the implicit HARQ attribute may be that the HARQ ID is from the location of the selected resource, and the HARQ process ID may be equal to floor(X / UL-TWG-periodicity) mod UL-TWG-numbHARQproc, where X=(SFN*SlotPerFrame*SymbolPerSlot+Slot_index_In_SF*SymbolPerSlot+Symbol_Index_In_Slot), and X is the symbol index at which the repetition bundle starts. In addition, the implicit HARQ attribute may be the HARQ RV sequence, which is determined by the RRC configuration (including RV cycle and RV0 repetition).

[0105] HARQ can also be periodic, with multiple TX opportunities for repetition in each cycle. In addition, the HARQ TX opportunity can be associated with a certain RV sequence, for example, {0,2,3,1}, {0,3,0,3} and {0,0,0,0} can be supported. The initial TX of the repetition can start from RV0, but its timing can be flexible.

[0106] In an unlicensed NR (NR-U) environment, when an NR-U device attempts to access an unlicensed channel, it may compete with inter-RAT devices as well as intra-RAT devices for channel access. The type and density of inter-RAT devices may depend on the unlicensed channel and the RAT may be Wi-Fi, LTE LAA, Bluetooth, etc. Intra-RAT devices may be other NR-U devices (e.g., WTRUs or gNBs). For example, for an NR-U WTRU, an intra-RAT device may be other NR-U WTRUs connected to the same gNB, or it may be an NR-U gNB or WTRU that is not associated with the same gNB. In attempting to access an unlicensed channel, the NR-U WTRU or gNB may need to fairly compete and coexist with inter-RAT and intra-RAT devices.

[0107] To ensure fair competition and coexistence, some regulatory domains may require (i.e., stipulate) that when a wireless node wants to access an unlicensed channel, the node needs to first perform a listen before talk (LBT) procedure for a period of time; and if no energy exceeding a threshold is detected, the wireless node may be allowed to transmit to the wireless channel for up to a maximum duration. Therefore, a similar LBT procedure may be expected for NR-U nodes.

[0108] Figure 2is an example transmission diagram in which the WTRU fails to successfully complete LBT. As described herein, for any transmission diagram, time 201 may be indicated on the horizontal axis, and the transmission may have multiple time units (e.g., time slots). The time slots may be labeled in time relative to time slot n. In this example, at 210, the WTRU may receive DL for PDCCH in time slot n-2 and time slot n-1, which may indicate UL resources for PUCCH in time slot n+2. At 211, the WTRU may not be able to successfully complete the LBT process for the scheduled PUCCH in time slot n+2, and therefore may need to restrict the transmission of the HARQ codebook that has been prepared for the TB carried in time slots n-2 and n-1. Thereafter, in this case the WTRU may have to restrict the transmission even if the transmission has a timing dependency that may affect the receiving entity. For example, if the WTRU is to transmit a PUCCH including a HARQ codebook and LBT fails, the WTRU may have to restrict the transmission of the PUCCH. At 212, the NR gNB may assume that the relevant TB in the previous PDSCH (for which the WTRU has prepared the HARQ codebook to transmit) was not correctly received by the WTRU and the gNB may need to retransmit the TB in the next transmission (e.g., the next time slots n-2 and n-1).

[0109] Figure 2 It is shown that in some cases, the NR-UgNB may not receive the HARQ codebook because the WTRU failed to complete the LBT process for the scheduled PUCCH resources. One way to address this problem may be to allow multiple opportunities for PUCCH transmission (e.g., signaled in the DCI).

[0110] Figure 3 is an example transmission diagram where the WTRU has more than one opportunity for PUCCH. Time 301 is indicated on the horizontal axis, with multiple time units (e.g., time slots). The time slots are labeled in time relative to time slot n. In this example, at 310, the WTRU may receive a DL of PDCCH (i.e., in time slot n-2 and time slot n-1), which may indicate PUCCH in time slot n+2 and time slot n+4. At 311, the WTRU may attempt to transmit in the first indicated opportunity in time slot n+2, but the LBT fails and therefore must wait until the next opportunity (i.e., time slot n+4). At 313, the WTRU attempts again and successfully completes LBT in time slot n+4 and transmits on the PUCCH.

[0111] In general, multiple resource opportunities may be scheduled over multiple slots that are spread out in time, or the resource opportunity may be scheduled in the same or two consecutive slots but each in a different 20 MHz BWP (i.e., each in a different 20 MHz unlicensed channel). Therefore, the PDSCH to HARQ Timing Indicator field, which is a scalar in NR, may carry multiple values. The WTRU may select the first slot if LBT is successful, otherwise proceed to the next opportunity, and so on. Figure 3 In the example of , the WTRU fails to successfully complete LBT for the first scheduled PUCCH in slot n+2 and waits for the second scheduled PUCCH in slot n+4, at which the WTRU successfully completes LBT and transmits the prepared HARQ codebook for the TBs (i.e., PDSCH) carried in slots n-2 and n-1. The set of scheduled PUCCHs may be indicated in the set of PDSCH to HARQ timing indicators.

[0112] However, the multiple-opportunity approach has disadvantages. Figure 3 If a failure occurs in time slot n+2), LBT will fail at the next opportunity (e.g. Figure 3 The chance of success in the unlicensed channel in slot n+4) may be referred to as the channel occupancy coherence time (COCT) and may depend on how many inter-RAT and intra-RAT devices are operating in the unlicensed channel and what type of traffic each device is engaged in. For example, if the majority of traffic for the unlicensed devices active in the band is video traffic, the COCT may be large and the chance of a successful LBT after a failed LBT may be large as long as the second LBT observation is long enough after the first LBT observation. If the COCT is large, it may not be effective to schedule multiple PUCCH resources within the same COT, which may have a duration of less than 5ms or 10ms depending on the class for which the COT is established. Assigning multiple PUCCH opportunities for each WTRU may be wasteful because the gNB has to assign multiple PUCCH resources (i.e., it may double or triple the number of resources used for PUCCH).

[0113] In addition, if the WTRU fails to transmit PUCCH within the timing window and LBT has failed on some PUCCH resources, the gNB may still not have the flexibility to request feedback at a later time. The NR process may first continue in HARQ in NR-U, where only one time slot for PUCCH transmission is indicated in each PDCCH. However, if the gNB does not receive the expected PUCCH, the gNB may provide one or more supplementary transmission opportunities for the PUCCH, whereby the WTRU has another opportunity to transmit HARQ feedback that was not previously sent and possibly other HARQ feedback (i.e., more than one time slot for PUCCH transmission may be indicated). In addition, even if the WTRU completes LBT and sends HARQ feedback, the gNB may not correctly detect the HARQ feedback due to interference or collision, which may result in misalignment between the gNB and the WTRU.

[0114] Efficient resource scheduling of PUCCH transmissions in the NR-U scenario can address these issues. To reduce overhead, the WTRU may be assigned exclusive resources (which are assigned to each WTRU) and non-exclusive resources (which are shared among multiple WTRUs). The non-exclusive resources may be assigned in a manner that reduces the probability of collisions between WTRUs. To implement the above approach, each WTRU may be assigned some exclusive PDSCH to HARQ timing indicators and one or more non-exclusive PDSCH to HARQ timing indicators (which may be shared among multiple WTRUs). The gNB may prioritize WTRUs that use non-exclusive PDSCH to HARQ timing indicators.

[0115] To enforce the priority of some WTRUs to manage non-exclusive resources, the PDSCH to HARQ timing indicator may include a priority parameter (e.g., a channel access priority level that determines the priority of the WTRU to access the medium to transmit its HARQ feedback). The gNB may explicitly assign priority parameters for specific non-exclusive resources to the WTRU. This may be assigned statically (i.e., through RRC configuration), semi-statically (i.e., through a combination of RRC configuration and DCI), or dynamically (i.e., through DCI).

[0116] In another approach, the WTRU may automatically select its access priority level for a particular non-exclusive resource. For example, the WTRU may select a priority parameter based on the number of non-exclusive resource failures it has experienced. Alternatively, the WTRU may select a priority parameter based on the number of exclusive and non-exclusive resources to which it is assigned. To this end, it may be assumed that the WTRU has N=N1+N2 HARQ resources, where N1 represents exclusive resources and N2 represents non-exclusive resources. In one example, the access priority level for N2 may be fixed and depend on the WTRU or service type. In another example, the access priority level may change as N2 increases (e.g., N2,1>=N2,1>=N2,3, where N2,x is the xth N2 resource). In another example, the access priority level may depend on the values ​​of N1 and N2, for example, a WTRU with N1=3 and N2=1 may have a lower priority than a WTRU with N1=1 and N3=3.

[0117] Figure 4 is an example transmission diagram in which a WTRU may have priority for non-exclusive PUCCH. Time 401 is shown on the horizontal axis and may be divided into time increments (e.g., time slots) relative to some n increment. In any of the figures described herein, a "space" may refer to a break in the diagram for example purposes only and is not intended to indicate missing or non-sequential time increments, but is only to save space in the examples shown. In addition, a space may be the same or similar to a time slot before or after the space unless otherwise indicated.

[0118] exist Figure 4 In the example of , at 410, WTRU 1 may receive a PDCCH in slot n-2 with an indication of exclusive PUCCH resources in slot n+2 and an indication of a non-exclusive PUCCH slot with a priority parameter of 1 in slot n+4. WTRU 1 may receive a PDSCH in slot n-2 and may decode the PDSCH, for which WTRU 1 may need to send HARQ feedback. At 411, WTRU 2 may receive a PDCCH in slot n-1 with an indication of exclusive PUCCH resources in slot n+3 and an indication of a non-exclusive PUCCH slot with a priority parameter of 2 in slot n+4. In this example, WTRU 2 may have a lower priority than WTRU 1. WTRU 2 may receive a PDSCH in slot n-1 and may decode the PDSCH, for which WTRU 2 may need to send HARQ feedback.

[0119] For the purpose of this example, it may be assumed that the gNB did not receive a transmission from WTRU 1 or WTRU 2 in its assigned PUCCH (i.e., slot n+2 or n+3, respectively). For example, in slot n+2, WTRU 1 may have performed LBT to transmit in the PUCCH where the LBT failed, and therefore WTRU 1 may have been unable to send a transmission in that PUCCH and must wait until slot n+4. Similarly, in slot n+3, WTRU 2 may have performed LBT which failed, and the WTRU must wait until slot n+4.

[0120] As a result of the failed first PUCCH attempts for both WTRUs, at 412, WTRU 1 and WTRU 2 may contend for PUCCH resources in slot n+4, with the LBT duration of WTRU 2 being set to a value that is statistically longer than the value of the LBT duration of WTRU 1, thereby increasing the probability that WTRU 1 acquires resources for transmission (i.e., WTRU 1 has a higher priority) because WTRU 1 has a shorter wait time before it transmits according to the LBT procedure. Since WTRU 1 has priority, it is able to successfully transmit its HARQ feedback.

[0121] In some cases, the gNB may not be able to detect the HARQ feedback sent by the WTRU due to collisions / interference on the gNB side. The reason why the gNB was not able to receive the transmission (e.g. failed LBT or lost UCI transmission) is not discernible on the gNB side. Due to the time association between the PDSCH and the corresponding feedback, if the gNB fails to detect the feedback at a predefined time position, the gNB may then retransmit all corresponding PDSCHs. While this can happen in NR operation in licensed channels, it occurs more frequently in NR-U due to highly fluctuating interference and possible collisions on the gNB side due to hidden nodes, etc. (e.g. undetectable on the WTRU side). This can cause a misalignment between the gNB and the WTRU (regarding which HARQ codebook the gNB has successfully received for the previous PDSCH), which may create a risk that the WTRU refreshes the HARQ codebook prematurely.

[0122] Figure 5is an example transmission diagram where the WTRU successfully completes LBT but the gNB fails to detect the PUCCH. Time may be displayed as increments of slots on the horizontal axis 501. At 510, the WTRU may receive indications for the PUCCH in slot n+2 in slots n-2 and n-1 and may also receive and decode the PDSCH in each slot. At 511, the WTRU may successfully complete LBT and transmit HARQ feedback for the PUCCH scheduled in slot n+2, but the gNB fails to detect the transmission due to interference or errors at the receiver. At 512, the gNB may send the next PDCCH to the WTRU in slot n+4 indicating that the PUCCH scheduled in slot n+6 is a supplemental PUCCH. The supplemental PUCCH may include the HARQ codebook for the WTRU to send in the PUCCH in slot n+6 for the previously scheduled PUCCH that should have been received in slot n+2, and any codebook associated with the PDSCH for slot n+4. At 513, the WTRU may successfully complete the LBT and send PUCCH with all HARQ codebooks in the supplementally assigned resources in slot n+6.

[0123] and Figure 5Unlike the example of , the problem of the gNB not receiving the expected PUCCH may occur in consecutive attempts, such as across a single channel occupancy time (COT) or across two COTs, etc. For example, the gNB may not receive the expected PUCCH that carries the HARQ codebook for the first PDSCH resource set, and the gNB may give the first supplemental PUCCH resource for HARQ codebook transmission, but until the time of the supplemental resource, the gNB may keep scheduling more PDSCH (i.e., the second PDSCH resource set) for the WTRU; therefore, on top of the previous one or more HARQ codebooks, there may be other HARQ feedback or other HARQ codebooks. The WTRU and the gNB may need to have the same understanding of how many and what HARQ codebooks the WTRU needs to transmit, and this common understanding may need to be achieved by keeping at least the amount of control information of the DCI short. Even though the WTRU may not be able to send aggregated HARQ feedback (e.g. due to LBT failure) or the gNB may not successfully detect the codebook during the first supplemental PUCCH resource, the gNB may then give the WTRU another chance by assigning a second supplemental PUCCH resource, but until the time of that supplemental resource, the gNB may schedule another set of PDSCH resources for the WTRU (i.e., the third set of PDSCH resources). The WTRU may now be expected to aggregate the HARQ feedback for all three PDSCH resource sets and transmit them during the second supplemental PUCCH resource. This situation continues until a certain point when there are no scheduled opportunities for the aggregated HARQ codebooks during the same COT, which means that these codebooks are postponed to the next COT. Furthermore, in the case where the gNB sends supplemental transmission opportunities, a misalignment between the codebook size expected by the gNB and the actual codebook size sent by the WTRU may result.

[0124] To address this issue, an additional field in the DCI may indicate to the WTRU that the upcoming PUCCH is a "supplementary transmission" and allow the WTRU to calculate the codebook size as it did in the previous PUCCH transmission. The Extended Downlink Assignment Indicator (EDAI) may be an additional field for the NR-U scenario described herein. This field in the DCI may carry the attributes of the scheduled PUCCH. This field may take into account PDSCH resource sets or groups with consecutive downlink assignment indicators (DAI) and mark them as a group. If the WTRU is expected to form a HARQ codebook for TBs within the current PDSCH resource set or group, the value of the EDAI field may be 0. If the WTRU is expected to form a HARQ codebook for TBs within the current PDSCH resource set or group and TBs within the immediately preceding PDSCH resource set or group, the value of the EDAI field may be 1. If the WTRU is expected to form a HARQ codebook for TBs within the current PDSCH resource set or group and TBs within the two immediately preceding PDSCH resource sets or groups, the value of the EDAI field may be 2. If the WTRU desires to form a HARQ codebook for TBs within the current PDSCH resource set or group and the TBs within the immediately preceding three PDSCH resource sets or groups, the value of the EDAI field may be 3. Then, if the WTRU desires to form a HARQ codebook for TBs within the current PDSCH resource set or group and the TBs within the immediately preceding Y PDSCH resource sets or groups, the value of the EDAI field may be Y. As described herein, this general rule may be applied to other scenarios where TBs are replaced with some other time or group unit, whereby the value of the EDAI field may be relative to the current time / group set and any previous time / group set (e.g., transmission, COT, etc.). Using this mechanism, a single DCI may request HARQ ACK feedback for all PDSCHs that may be transmitted in one or more PDSCH groups in the same PUCCH.

[0125] When EDAI is non-zero and the WTRU attempts to aggregate two or more previously prepared HARQ codebooks with the current codebook, the WTRU may insert a field between the bit streams of one codebook and the next codebook so that the gNB can distinguish and parse the codebooks; the field may be represented as a HARQ codebook delimiter with a specified bit width (e.g., 2 or 4). When multiple HARQ codebooks are aggregated, the WTRU may insert a HARQ codebook delimiter after each HARQ codebook. In one example, if the WTRU has received consecutive PDCCHs with EDAI attributes that do not have consecutive values, the WTRU may infer that one or more PDCCH sets that result in discontinuous EDAI values ​​have not been detected. In this case, the WTRU may insert a HARQ codebook delimiter for each missing EDAI value. For example, consider that the WTRU receives a PDCCH set with the value EDAI=0, and then in the next set of time slots or even the next one or more COTs, the WTRU receives a PDCCH set with the value EDAI=2. This may indicate that the WTRU has lost one or more PDCCHs with EDAI=1, and therefore the WTRU may not know how many TBs were transmitted during the one or more PDCCHs with EDAI=1. Therefore, when the WTRU aggregates the codebooks of the first received set of one or more PDCCHs with EDAI=0 and the second received set of one or more PDCCHs with EDAI=2, the WTRU may insert additional HARQ codebook delimiters for the lost set of one or more PDCCHs with EDAI=1. To further illustrate this, the WTRU may aggregate the following HARQ codebooks: HARQ codebook EDAI0, HARQ codebook delimiter, HARQ codebook delimiter, HARQ codebook EDAI2. In this example, a PDSCH group (e.g., a PDSCH in a COT) is dynamically marked with each EDAI index. In this example, a HARQ codebook for each group indexed by the EDAI associated with the group may be accumulated within each PDSCH group. Alternatively, a HARQ codebook for each PDSCH group indexed by the EDAI associated with the group may be accumulated across all groups.

[0126] Figure 6is an example transmission diagram of a WTRU preparing the HARQ codebook based on the DAI (i.e., to calculate the codebook for the expected set of PDSCHs as expected by the gNB) and based on the EDAI (i.e., to decide how many of the immediately preceding HARQ codebook sets should also be included). At 610, the WTRU may receive in slot n-2 an indication for the PUCCH in slot n+2, where DAI=1 and EDAI=0. At 611, the WTRU may receive in slot n-1 an indication for the PUCCH in slot n+2, where DAI=2, since the codebook will be based on the set of two PDSCHs received so far, and EDAI=0. At 612, the WTRU will perform its scheduled LBT in slot n+2, and the gNB will not receive the PUCCH in this example because the LBT failed or the LBT was successful but there was interference at the receiver. At 613, the WTRU will receive a normal resource assignment (e.g., PUCCH in n+6 with DAI=3 since this is the third PDSCH) but indicating EDAI=1 since the gNB did not receive PUCCH in slot n+2 and thus the indication should also include the immediately preceding HARQ codebook set. At 614, the gNB will not receive the PUCCH, similar to the case at 612 for illustration. Therefore, at the next resource assignment at 615, the WTRU may receive an indication for the PUCCH for slot n+9 with DAI=3 and EDAI=2 since the two closest codebook sets should now be included. At 616, the gNB may finally receive the PUCCH after a successful LBT performed by the WTRU in the indicated slot n+9.

[0127] Figure 7is an example transmission diagram of a WTRU preparing a HARQ codebook based on the DAI (i.e., to calculate the codebook for the desired PDSCH set) and based on the last value of the EDAI (i.e., to decide how many of the immediately preceding HARQ codebook sets should also be included). The value of the EDAI may be different during a set of PDCCH resources. For example, consider two consecutive PDCCH resources at 712 and 714 (e.g., in slots n+2 and n+4) with consecutive DAI values ​​indicating that the WTRU is expected to report an upcoming PUCCH (e.g., in slot n+6) for the HARQ codebook of the associated PDSCH resource. In addition, the PUCCH for the previous PDSCH resource set at 710 and 711 (e.g., in slots n-2 and n-1) may be scheduled between these two PDCCH resources (e.g., in slot n+3). At 712, the value of EDAI may be 0 (e.g., in the PDCCH in slot n+2), but when the gNB does not receive the expected codebook for the previous PDSCH set at 713, then at the next PDCCH (e.g., in slot n+4), the gNB may change the EDAI to 1 (at 714) and may also increase the size of the PUCCH (i.e., it may even relocate the PUCCH resources to a later slot to accommodate the larger PUCCH). At 715, the WTRU may then prepare an aggregate codebook that includes the earlier HARQ codebook (e.g., the codebook that the gNB did not receive for slots n-2 and n-1) and the new HARQ codebook (e.g., for the two PDSCH resources in slots n+2 and n+4).

[0128] The WTRU may calculate the dynamic codebook size with reference to the DAI value. Due to the 2-bit size of the DAI, the field may wrap around after four PDCCH / PDSCH transmissions, where all four transmissions refer to the upcoming PUCCH. For example, if five consecutive PDCCH / PDSCH transmissions refer to the upcoming PUCCH, the DAI values ​​in the PDCCH may be “mod(dai,4), mod(dai+1,4), mod(dai+2,4), mod(dai+3,4), mod(dai,4), mod(dai+1,4)”, respectively, which indicates the wrap-around effect. However, if less than four consecutive PDCCHs are lost, the wrap-around does not generate any error (i.e., the WTRU simply reports NACK for the lost PDCCH resources because both the PDCCH and PDSCH are lost). In addition, if the WTRU loses four or more consecutive PDCCH transmissions, the WTRU may not be able to calculate the actual number of lost PDCCH resources, which may result in misalignment because there is no way to correctly calculate the codebook size. Losing 4 or more consecutive PDSCHs on a licensed carrier is unlikely, but is more likely to occur in NR-U due to collision / interference on the WTRU side. This issue can be addressed by increasing the DAI size to greater than 2 bits (e.g., 3 or 4 bits), thereby reducing the likelihood of losing 8 or 16 consecutive PDCCHs in the case of independently accumulating DAI within each group (i.e., accommodating the possibility of losing more than 4 PDCCHs). In the case of accumulating DAI across multiple PDSCH groups indexed by EDAI, the dynamic codebook size can be a multiple of the number of PDCCH / PDSCH transmissions (N) for each group (i.e., N x (3 or 4 bits)).

[0129] Figure 8 810 is an example transmission diagram of a WTRU aggregating HARQ codebooks based on EDAI for one or more COTs. Here, the WTRU may aggregate HARQ codebooks from an earlier COT (i.e., the immediately preceding COT in this example) if the EDAI field indicates to do so (i.e., EDAI=TBD1). As shown, there may be two COTs 810 and 820. COT 810 may be a slot increment relative to n, and COT 820 may be a slot increment relative to j (e.g., n=j). In general, there may be more than two COTs, but as shown COT 820 is after COT 820, at 811 (i.e., slot n-2), the WTRU receives an indication of a PUCCH for slot n+2, where DAI=1 and EDAI=0. At 812 (i.e., slot n-1), the WTRU may be indicated for a PUCCH in slot n+2, where DAI=2 and EDAI=0.

[0130] At 813, the WTRU may be expected to transmit a HARQ ACK to the indicated PUCCH resource at the end of the COT 810 (i.e., slot n+2), but the LBT may be unsuccessful (e.g., failed LBT or gNB failed to receive) and the COT 810 ends without the WTRU transmitting. The gNB and the WTRU may not know when the next opportunity for PUCCH transmission will be. To address this issue, at 821 (i.e., slot j), the gNB may send a PDCCH with an indication (e.g., in DCI or RRC) that EDAI=TBD1 to the WTRU in the next COT 820. The indication indicates to the WTRU to send a PUCCH in slot j+k with an aggregated HARQ codebook or HARQ codebook that was not transmitted during the last PUCCH opportunity in the earlier COT 810. The EDAI may indicate a specific PDSCH group or a specific COT, such as a PDSCH group that could not transmit a PUCCH in a previous COT. At 822, the WTRU may successfully complete LBT for the PUCCH (e.g., indicated by DCI or configured by RRC) and aggregate the HARQ ACKs from the previous and current COTs and send them to the gNB. Although this example only discusses two COTs, the same technique may be used for one or more COTs.

[0131] In general, if the WTRU fails to complete the LBT and restricts the transmission of PUCCH, the WTRU may keep the HARQ codebook until the next COT, and if the WTRU receives a PDCCH with EDAI=TBD1, the WTRU may do one of the following: 1) if the DCI indicates only the upcoming PUCCH, without any PDSCH, the WTRU may transmit the codebook in the indicated upcoming PUCCH resources; or, 2) if the DCI indicates the upcoming PUCCH and PDSCH resources, the WTRU may aggregate the earlier codebook and any new HARQ codebook and transmit the aggregated codebook in the indicated upcoming PUCCH resources. Even if the WTRU successfully completes the LBT process and transmits PUCCH, the WTRU may keep the HARQ codebook until the next COT and / or until the WTRU receives a PDCCH with a value less than EDAI=TBD1 (e.g., EDAI=0), after which the WTRU may discard the previous HARQ codebook.

[0132] The TBD1 value may be, for example, 3 (if the EDAI has a bit width of 2), or the TBD1 value may be 7 (if the EDAI has a bit width of 3). Alternatively, TBD1 may be 1, where this value in the first unicast PDCCH to the WTRU in the new COT has the same interpretation as above. As described herein, Figure 8The EDAI value shown and used in the example represents a value that is used to indicate to the WTRU to aggregate all pending HARQ codebooks in a certain group / time (e.g., TB, COT, etc.) until the next uplink opportunity, and the value can be one or more numbers, letters and / or symbols that can express this meaning.

[0133] In one scenario, there may be two consecutive COTs where the gNB has sent a TB to the WTRU and the WTRU fails to complete the LBT during the scheduled PUCCH opportunity or the gNB fails to correctly detect the PUCCH, which results in a set of two pending HARQ codebooks on the WTRU side. In addition, if the field EDAI in the received DCI has the value TBD2, it may indicate that the WTRU should aggregate the HARQ codebook of the current COT (if any) with the pending HARQ codebook (e.g., each prepared during the first two immediately preceding COTs) in the scheduled PUCCH resources indicated in the same DCI with EDAI=TBD2. In other scenarios, any EDAI value of TBD#, # may represent a numerical value associated with the number of COTs (e.g., counting the current and / or any previous COTs to reach this numerical value). The EDAI value of TBD# may indicate a numerical value associated with a specific COT.

[0134] In some cases, when the WTRU sends a HARQ codebook in a scheduled PUCCH, the WTRU does not discard the HARQ codebook unless the attribute of the next scheduled PUCCH has EDAI = 0. This helps the WTRU to ensure that the gNB has correctly decoded the previously sent PUCCH and may not need to retransmit the HARQ codebook again.

[0135] Fig. 9is an example transmission diagram where PUCCH resource assignment is outside the current COT and PUCCH from a later COT is used. In this example, there may be two COTs 910 and 920. At 901, the gNB may schedule a PUCCH in a theoretical time slot n+3, which may be outside the current COT 910. If the PDSCH to HARQ Timing Indicator field in the scheduled PDCCH indicates a timing instance outside the determined end time of the current COT, the WTRU may infer that the scheduled PUCCH is outside the current COT 910. At 902, if the WTRU determines that the scheduled PUCCH falls after the end of the current COT, the WTRU may not perform a PUCCH transmission and may keep a pending HARQ codebook for the upcoming transmission. In a subsequent COT 920 established by the gNB, when the WTRU receives a new PDCCH with EDAI (e.g., indicated in DCI or RRC) with the attribute of scheduling PUCCH for slot j+2 of COT 920. At 904, the WTRU may send the pending HARQ codebook and any new codebook (i.e., aggregated HARQ ACK) in the newly scheduled PUCCH. In the first PDCCH / DCI in the new COT, the gNB may set EDAI=TBD1, similar to Figure 8 , for indicating to the WTRU that a pending HARQ codebook is expected to be transmitted along with any newly formed HARQ codebook. Note that the arrows show that the HARQ ACK for each of the PDSCHs is sent in slot j+2. Not shown in the figure, if the WTRU does not receive a new PDCCH in a subsequent COT for the corresponding PDSCH received in the current COT, the WTRU may transmit the associated HARQ codebook in the PUCCH resources provided by higher layers.

[0136] In some instances, if the WTRU detects a PDCCH in the current COT but the DCI does not include the PDSCH to HARQ timing indicator field, the WTRU may assume that the gNB has not allocated PUCCH resources to the WTRU for the corresponding PDSCH reception in the current COT. Therefore, the WTRU may transmit the pending HARQ codebook on the PUCCH resources in the subsequent COT, with Figure 8 and 9 In this case, assuming that the WTRU receives PDSCH in slot n in the current COT, the WTRU may determine PUCCH resources in slot n+k in the subsequent COT, where k is the number of slots provided by the PDSCH to HARQ timing indicator field in the DCI received in the higher layer or the subsequent COT.

[0137] In some cases, if the WTRU finds that the scheduled PUCCH falls after the end of the current COT, the WTRU may transmit the PUCCH after performing the appropriate LBT procedure and after the COT has ended. Even if the COT duration has expired, the WTRU may still transmit its PUCCH like any device in an unlicensed channel (e.g., but not subject to the COT), but the WTRU will have to perform an LBT procedure, the category of which depends on how long the scheduled PUCCH is after the end of the COT. If the scheduled PUCCH is within 16μs of the end of the COT, the WTRU may transmit the PUCCH with Cat-1 LBT (which may be considered similar to no LBT). If the scheduled PUCCH is within 25μs of the end of the COT, the WTRU may transmit the PUCCH with Cat-2 LBT (which may be referred to as one-shot LBT). If the scheduled PUCCH is after 25 μs of the end of the COT, the WTRU may transmit PUCCH with Cat-3 LBT and the WTRU may use the highest priority level to calculate the listening interval. If the scheduled PUCCH is after 25 μs of the end of the COT and the WTRU is to transmit a TB within the configured granted resources after the PUCCH transmission, the WTRU may transmit PUCCH with Cat-4 LBT. In the above case, the WTRU may keep the HARQ codebook until the next COT established by the gNB, because the gNB may require the WTRU to retransmit the HARQ codebook (i.e., by setting EDAI=TBD1).

[0138] As described herein, for successful operation in the NR-U LBT procedure, LBT can be an efficient way for inter-RAT and intra-RAT coexistence. However, the listening gaps in LBT are wasted bandwidth resources, and the more frequently the LBT procedure is invoked, the less efficient the channel access is. Therefore, it is beneficial to have one switch from DL to UL in the COT, whereby the LBT procedure can be invoked once. The gNB may be able to schedule DL / UL for the WTRU in the COT using a single switching point, where there are no gaps or the gaps are very small. If there is an LBT rule with a gap of less than 16μs (which can be obtained in LBT Category-1), the provision helps with this, and if the gap is less than 16μs, the responding device (e.g., WTRU) does not have to perform any listening gaps. For example, some 802.11 technologies can take advantage of this and the responding station can send an acknowledgment response of a frame that is exactly 16μs in duration. Therefore, the NR-U frame structure can be modified for these efficient coexistence scenarios without LBT in the COT, where the gNB can address multiple WTRUs within the COT.

[0139] For reference, a switching gap (from DL to UL) may be indicated and scheduled within the SFI as follows “DL(WTRU1), DL(WTRU2), LBT, UL(WTRU1), DL(WTRU3), LBT, UL(WTRU2), DL(WTRU1), …”, where the switching gap may be one OFDM symbol and the duration of the gap may be greater than 16 μs, depending on the parameter set. In such a case, the WTRU may need to do something other than Cat-1 LBT (e.g., if the duration is less than 25 μs then the WTRU may perform Cat-2 LBT). However, performing LBT may mean that the WTRU must be in receive mode, albeit using a limited portion of its baseband unit, and means that by the time the WTRU successfully completes LBT, the WTRU may need some switching time to switch to transmit mode.

[0140] In one scenario, the gNB may schedule multiple WTRUs in a manner that does not require DL / UL switching gaps. This may be a scheduling problem for the gNB whereby a DL symbol is addressed to a first WTRU and the following UL symbol is for a second WTRU. For example, the scheduling may be DL(WTRU1), DL(WTRU2), UL(WTRU1), DL(WTRU3), UL(WTRU2), DL(WTRU1), …. In this example, WTRU1 may be notified of its upcoming UL transmission and informed to prepare for UL transmission without gaps.

[0141] In general, for these examples regarding switching UL / DL, slot boundaries may be intentionally ignored, but it is understood that UL symbols may be located at the last few symbols of a slot. In addition, the DL and UL portions may have different sizes. In addition, the notation DL(WTRU1) may represent one or more DL symbols, such as at the beginning of a slot for a first WTRU (i.e., WTRU1), which may carry PDCCH and / or PDSCH resources.

[0142] Fig.10is an example transmission diagram where the WTRU checks the attributes of the scheduled PUCCH resources and if No LBT-PUCCH has a true value, the WTRU does not perform any listening interval (i.e., no gap) just before the PUCCH. At 1011, the WTRU may check the attributes of the scheduled PUCCH resources in the DCI in the PDCCH with a matching RNTI; here the gNB may indicate to the WTRU the PUCCH in slot n+3, DAI=0, and No LBT-PUCCH=True. At 1012, the gNB may indicate to the WTRU the PUCCH in slot n+3, DAI=1, and No LBT-PUCCH=True. If No LBT-PUCCH has a true value, the WTRU may infer that for the upcoming PUCCH (i.e., slot n+3) (with associated time and frequency attributes), there is no gap just before the PUCCH UL transmission, and therefore the WTRU may not need to perform any listening interval just before the PUCCH, as shown at 1013. The gNB may schedule DL symbols before the PUCCH resources, whereby no DL channels are addressed to the WTRU.

[0143] Additionally at 1013, if the WTRU finds scheduled PUCCH resources in the DCI in the PDCCH with a matching RNTI where the No LBT-PUCCH subfield has a true value, the WTRU may temporarily overwrite the value of the most recent SFI (e.g., only for the slot where the PUCCH is located) and select one or more OFDM symbols before the scheduled PUCCH as the 'X' symbol during which the WTRU transitions from downlink reception to UL transmission. The WTRU may overwrite the most recent SFI value when determining the 'X' symbol, whereby the gNB may take dynamic behavior to schedule PUCCH resources for the WTRU, which takes advantage of Cat-1 LBT (e.g., or no LBT in a 16 μs period).

[0144] In another scenario, the gNB may provide a gap interval that is sufficient for the WTRU to perform a 25 μs LBT procedure (e.g., one-time LBT) and switch from DL to UL symbols. The schedule may be “DL(WTRU1), DL(WTRU1), DL(WTRU1), DL(WTRU1), LBT, UL(WTRU1), …”, where the LBT duration is more than one or two OFDM symbols (depending on the parameter set). The WTRU may check the scheduled PUCCH resources in the DCI with the matching RNTI in the PDCCH. If the one-time LBT PUCCH has a TBD3 value, the WTRU may infer that there is a gap of one or more symbols just before the PUCCH UL transmission for the upcoming PUCCH (i.e., with associated time and frequency attributes), and therefore, the WTRU may perform a 25 μs listening interval just before the PUCCH and just after the switch may be prepared if the LBT is successful. If the WTRU finds a scheduled PUCCH resource in the DCI in the PDCCH with a matching RNTI where the No LBT-PUCCH subfield has the value TBD3, the WTRU may temporarily overwrite the value of the most recent SFI (e.g. only for the slot where the PUCCH is located) and select one or more OFDM symbols before the scheduled PUCCH as 'X' symbols (see Table 3, e.g. D / X / U symbols) during which the WTRU may transition from downlink reception to UL transmission. However, the transition may be conditional on a successful LBT during the 25 μs interval just before the transition.

[0145] In a Granted (GC) or Unlicensed transmission configured in NR, the WTRU may be configured to transmit TBs in a sequence of (i.e., RRC configured) Unlicensed resources with up to K = (1, 2, 4, 8) repetitions. There are similar or identical Unlicensed procedures in NR-U, where some WTRU behaviors regarding channel access and related LBT procedures need to be modified. When the gNB has established a COT with some Unlicensed resources, the WTRU may start Unlicensed transmission within the COT established by the gNB. For Unlicensed resources within the COT, the WTRU may perform the LBT procedure to access the resources.

[0146] In an example, the WTRU may perform an LBT procedure (e.g., LBT Cat-2, 3, or 4) once, for example, just before the first unlicensed resource that the WTRU attempts to access, and then if the LBT procedure is successful, the WTRU may access the remaining unlicensed resources within the COT with no LBT (i.e., LBTCat-1) or one LBT (LBT Cat-2) or LBT Cat-3. Depending on the value of K, the WTRU may reach the end of the COT without completing K repetitions of a TB (i.e., as specified in the K repetition unlicensed UL transmission).

[0147] In one example, the WTRU may perform the more reliable LBTCat-4 before accessing the first unlicensed resource outside the COT, and for accessing subsequent unlicensed resources outside the COT, the WTRU may perform no LBT or Cat-1.

[0148] In one example, the WTRU may perform LBT Cat-3 before accessing the first unlicensed resource outside the COT, and for accessing subsequent unlicensed resources outside the COT, the WTRU may perform no LBT or one LBT.

[0149] In one example, the gNB may configure or may instruct the WTRU such that the WTRU performs an LBT procedure (Cat-1) before accessing the first and each subsequent unlicensed resource outside the COT.

[0150] In an example, the WTRU may restrict transmission on resources outside the COT.

[0151] As described herein, there may be situations in NR-U transmissions where the WTRU needs to transmit outside the original COT and more than one COT is needed. If there is more than one COT, the WTRU may need to send an acknowledgement in another COT and adjust the contention window.

[0152] The transmission of the acknowledgment may be delayed to a separate COT, for example because the data transmission is in COT1 and the acknowledgment transmission may be in COT2. In this case, the acknowledgment transmission may be after a successful LBT. In one example, the reception of the HARQ codebook may also require the acknowledgment, for example, the WTRU performs LBT and transmits the UL acknowledgment in the UL timeslot. The gNB needs to confirm the reception of the acknowledgment in the subsequent DL timeslot. In this way, the WTRU may know whether the transmission was successful, and thus the WTRU may adjust its contention window accordingly for the next LBT.

[0153] In the example where the ACK is in a separate COT, the UL acknowledgement transmission from the WTRU may be polling based. To improve efficiency, a group polling mechanism may be used.

[0154] In the example where the ACK is in a separate COT, the gNB may perform LBT to acquire the channel and then the gNB may transmit a group-common DCI for acknowledging the poll to one or more WTRUs. A set of frequency / time resources may be allocated for acknowledgment transmissions from multiple WTRUs. The WTRU may receive the group-common DCI and have one or more UL acknowledgments to transmit and may transmit the acknowledgments using the allocated frequency / time resources. The WTRU may perform LBT for a fixed duration prior to its UL transmission, or the WTRU may not need to perform LBT and transmit in the allocated resources. In one instance, the WTRU may randomly select one or more resources for transmission.

[0155] In the example where the ACK is in a separate COT, the gNB may perform LBT to acquire the channel and then the gNB may transmit a set of DCIs for acknowledgment polling to a group of WTRUs. A set of frequency / time resources may be allocated for acknowledgment transmissions from multiple WTRUs. The WTRU may receive the group common DCI and have one or more UL acknowledgments to transmit and may transmit the acknowledgments using the allocated frequency / time resources. In one example, the WTRU may randomly select one or more resources for transmission.

[0156] Fig.11 is an example procedure for contention window adjustment due to the cumulative number of acknowledgments to be transmitted.

[0157] In general, the transmission of an acknowledgement in NR-U may require the performance of LBT. The device may not be able to transmit due to a failure in LBT, or the device may transmit an acknowledgement but the transmission may fail due to a conflict. In this case, the device may wait for the medium / channel to be available again and perform LBT. If the transmission fails, the device may need to increase the contention window size, thereby extracting a larger random backoff value. However, delayed acknowledgement transmission may result in delayed data transmission and create a congested channel. To address this issue, if there are accumulated acknowledgements, the device may reduce the contention window size or reduce the remaining backoff duration. In this case, the device may have a separate random backoff process for acknowledgement transmission.

[0158] like Fig.11 As shown, at 1102, the WTRU may determine a contention window size CWp, where CW min ≤CW p ≤CW max , and The CW min and CW max It may be predefined / predetermined or signaled. At 1104, the WTRU may extract a random backoff number, R∈[0,CW p]. At 1106, the WTRU may detect that the signal energy level is below a predefined threshold for a fixed duration and that the WTRU may have a pending ACK / NACK. At 1108, the WTRU may check if R>0 holds.

[0159] If R is greater than 0, then at 1110, the WTRU may continue to monitor the channel / medium for the T time slot. If the channel is idle during the time slot, then at 1114, the WTRU may set R=R-1. If not idle, then at 1112, the WTRU may check the number of accumulated acknowledgments to be transmitted, Nack, and the WTRU may set R=f(R, Nack). ack ). The function f may be predefined or predetermined. In one example, The WTRU may maintain the updated R value and continue to monitor the channel.

[0160] If R is not greater than 0 (i.e., R reaches 0), then at 1116, the WTRU may transmit an ACK / NACK to the gNB. At 1118, the WTRU may know / determine whether the transmitted ACK / NACK was successful. If successful, then at 1020, the WTRU may set the CW p =CW min and extracts a new random backoff number for the next ACK / NACK transmission (at 1104). If the transmission of the ACK / NACK is unsuccessful, then at 1112, the WTRU may adjust the remaining random backoff value R. The WTRU may set R = f(R, N ack ).

[0161] exist Fig.11 In the example process of FIG. 1 , the WTRU may have Nacks saved for the cumulative number of acknowledgments. The manner in which Nacks are maintained on the WTRU side may be implementation dependent. For example, once the WTRU receives a valid DCI corresponding to a PDSCH transmission to the WTRU, the WTRU may increase the number of Nacks by 1. Once the WTRU notices that the previous acknowledgment transmission was successful, the WTRU may reset the value Nack. For example, the WTRU may set in This could be the number of previously successfully transmitted acknowledgments.

[0162] As described herein, in NR-U transmissions, after performing a successful LBT procedure, the WTRU or gNB may continue to transmit in an unlicensed channel for a maximum duration. In some cases, it may be necessary to share the COT. When a device such as a WTRU or gNB starts a COT in an unlicensed channel, it may also be possible to share the COT with another device (e.g., a gNB or WTRU, respectively), where the second device transmits during the COT. For example, if a gNB starts and "owns" a COT (i.e., a COT owned by the gNB), it may share the COT with one or more WTRUs, or if a WTRU starts and "owns" a COT (i.e., a COT owned by the WTRU), it may share the COT with its gNB. For better coexistence and more efficient transmission and reception in unlicensed channels, COT sharing may be subject to some rules. The use of COT sharing in NR-U may enable better coexistence and more efficient transmission and reception in unlicensed channels.

[0163] In a configured grant (CG) or unlicensed transmission, the WTRU may perform an LBT procedure (e.g., LBT CAT-3 or CAT-4) and establish a COT, where the LBT procedure is associated with a priority level. The WTRU may transmit its pending one or more TBs to its gNB using the CG transmission rules. The WTRU may then share its COT (the WTRU's WTRU-owned COT) with the gNB. The gNB may use this shared COT for some purposes. For example, the gNB may send a CG-DFI to the WTRU, which carries HARQ feedback for the immediately preceding one or more TB transmissions, or one or more TB transmissions before the COT is established. The gNB may also transmit one or more TBs to the same WTRU or to one or more other WTRUs.

[0164] For more efficient COT sharing, the WTRU may indicate to the gNB the attributes of the COT. These attributes may be sent by the WTRU to the gNB in ​​the last or last few CG PUCCH transmissions, and these attributes may be carried in the CG-UCI. The COT attributes carried in the CG-UCI may include the following: the duration of the COT (e.g., duration interrupt, such as total duration, duration expected to be used by the WTRU that owns the COT, and / or the remainder of the COT); the access category (AC) or access priority level for which the COT is established; whether the gNB is allowed to use the COT for DL ​​transmissions to other WTRUs; and / or whether the gNB is allowed to use the COT to schedule UL transmissions for other WTRUs.

[0165] When the gNB starts a transmission in a WTRU-shared COT, the gNB may announce the COT attributes to other WTRUs. The (WTRU-shared) COT attributes may be the portion of the COT attributes that the gNB sends at the beginning of the COT and / or retransmits at the beginning of subsequent slots of the COT. The gNB may send the COT attributes at the beginning of the COT or at the beginning of a shared transmission.

[0166] COT sharing may be performed between two or more WTRUs (e.g., two WTRUs participating in a CG transmission to their gNBs). For example, a WTRU may start a COT and transmit its pending one or more TBs in the CG PUSCH. WTRU2 may then use the same COT to transmit its own CG PUSCH. However, WTRU2 may need to be informed of the COT that WTRU1 has. In one approach, WTRU1 may send its COT attributes to the gNB, indicating that other WTRUs may use the rest of the COT. The gNB may then notify other WTRUs of the COT attributes in the Group Common (GC) PDCCH.

[0167] The COT established by the WTRU may be for a CG or an autonomous uplink (AUL) transmission. When the COT is shared by the gNB, the shared COT may be used between the CG (or AUL) and scheduled or grant-based UL transmissions. For example, the gNB may use the COT owned by WTRU1 to schedule a grant-based (or scheduled UL) for WTRU2. However, to do this, the gNB may need to know that WTRU2 has one or more TBs pending for transmission. In some cases, the gNB may have received a scheduling request (SR) from the WTRU in a previous or immediately preceding COT, and / or may not have the time or scheduling resources to schedule UL transmissions for the WTRU in the COT. Alternatively, the gNB may schedule SR resources for all WTRUs in the first or first few time slots after the gNB starts using the shared COT, where the SR resources may be used to indicate to the gNB that it has one or more TBs pending. After receiving the SR from the WTRU, the gNB may schedule the UL in the remainder of the shared COT owned by WTRU1.

[0168] When a WTRU is to share its owned COT with its gNB, the WTRU may perform one or more actions to ensure that the gNB is able to start its downlink transmission within a gap defined by regulatory requirements (e.g., the gap may be 25 μs in duration). If the gNB starts transmission within the gap, then COT sharing may be performed within regulatory requirements. Otherwise, if the gNB is not able to start transmission within the duration of the gap, then the gNB may have to go through a full LBT procedure (CAT3 or CAT4) before being able to transmit. In order to increase the chances of the gNB successfully using the shared COT owned by the WTRU, the WTRU may perform one or more of these actions.

[0169] One such action may be that the WTRU extends the cyclic prefix (CP) of one or some last symbols to align the end of its transmission within the regulatory duration (e.g., 25 μs) before the start of the next slot or the next opportunity for the gNB to start a mini-slot. Note that the WTRU may indicate this CP extension to the gNB in ​​advance, for example in the CG-UCI.

[0170] One such action may be for the WTRU to transmit a sounding reference signal (SRS) in the last or some symbols within the regulatory duration (e.g. 25 μs) before the start of the next timeslot or before the next opportunity when the gNB can start a mini-slot.

[0171] In the COT attributes, some measurements from the WTRU that has acquired the COT may also be reported (e.g., RSSI, Reference Signal Received Power (RSRP), etc.). COT sharing may be prioritized between a set of WTRUs and a gNB, where one device acts as a primary (or master) node and the others are secondary (or slave) nodes.

[0172] Fig.12 is an example transmission diagram for basic COT sharing. In general, basic COT sharing may be used in scenarios where the WTRU has low traffic load or in lower density situations where the hidden node problem is less pronounced. Fig.12, each box may represent one or more time slots. The COT duration 1220 may include the WTRU1 COT 1222 and the COT shared portion 1224. Initially at 1201, the WTRU may acquire the COT (e.g., to transmit in a pre-configured CG / licensed-free resource) by performing LBT. On the first transmission after acquisition, the WTRU may transmit the COT attributes and other attributes related to the WTRU CG transmission to the gNB (at 1202). These attributes may be carried on the UCI multiplexed on the PUSCH. Once the PUSCH transmission is completed, at 1203, the gNB may take over the COT (i.e., share the COT), where one or more of the following may occur: the gNB announces the COT attributes in the GC-PDCCH (also at 1203); at 1204, the gNB transmits the PDCCH with the WTRU allocation; at 1205, the gNB / WTRU transmits the PDSCH / PUSCH based on the PDCCH allocation; and / or at 1206, the gNB / WTRU transmits the PUCCH / PDSCH (i.e., for ACK) based on the received PDSCH / PUSCH.

[0173] Alternatively, the COT sharing process may include other steps to limit the influence of hidden nodes. Fig.13 is an example transmission diagram of COT sharing to limit hidden node impact. The COT duration 1320 may include a WTRU1 COT 1322 and a COT shared portion 1324. Initially, at 1301, the WTRU may acquire a COT based on LBT (e.g., to transmit in a pre-configured CG / licensed-free resource). At 1302, on the first transmission after acquisition, the WTRU may transmit COT attributes to the gNB. These COT attributes may be carried by a short transport block, a short PUCCH, or a modified SR that uses UCI on PUCCH to multiplex the COT on the PUSCH. Upon receiving the WTRU COT attributes at the gNB, the gNB may transmit shared COT attributes (at 1303), which may be the exact COT attributes requested by the WTRU, or may be a modified set of the COT attributes requested by the WTRU, which includes the WTRU's reserved attributes and other shared COT attributes. At 1304, the WTRU may then transmit its desired data to the gNB in ​​the PUSCH. When the PUSCH transmission is complete, the gNB may take over the COT, where the gNB may transmit a PDCCH with a WTRU allocation (1305), the gNB / WTRU may transmit a PDSCH / PUSCH based on the PDCCH allocation (1306), and / or the gNB / WTRU may transmit a PUCCH / PDSCH (for ACK) based on the received PDSCH / PUSCH.

[0174] Although the features and elements are described above in specific combinations, it will be understood by those skilled in the art that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in a computer program, software, and / or firmware incorporated in a computer-readable medium to be executed by a computer and / or processor. Examples of computer-readable media include, but are not limited to, electronic signals (transmitted via wired and / or wireless connections) and / or computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memories (ROMs), random access memories (RAMs), registers, buffer memories, semiconductor memory devices, magnetic media (e.g., internal hard disks and removable disks), magneto-optical media, and optical media (e.g., CD-ROM disks and / or 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, and / or any host computer.

Claims

1. A method performed by a wireless transmit / receive unit (WTRU), the method comprising: receiving one or more physical downlink shared channels (PDSCHs) in a first channel occupancy time (COT); receiving a physical downlink control channel (PDCCH) with control information in a second COT; receiving one or more PDSCHs in the second COT; aggregating hybrid automatic repeat request (HARQ) feedback for the one or more PDSCHs of the first COT and the one or more PDSCHs of the second COT based on the control information; and transmitting the aggregated HARQ feedback in a physical uplink control channel (PUCCH) of the second COT based on resources indicated in the control information.

2. The method according to claim 1, the method further comprising performing listen-before-talk (LBT) before transmitting the aggregated HARQ feedback in the PUCCH of the second COT.

3. The method according to claim 2, the method further comprising: decoding the one or more PDSCHs of the first COT and the one or more PDSCHs of the second COT, and determining that each PDSCH of each COT requires HARQ feedback.

4. The method according to claim 3, wherein the control information includes an enhanced downlink assignment indicator (EDAI), the EDAI indicating a group or time for aggregating HARQ feedback therein.

5. The method according to claim 4, the method further comprising determining to aggregate the first PDSCH and the second PDSCH based on the EDAI.

6. The method according to claim 1, wherein the indicated resources are exclusive or non-exclusive.

7. The method according to claim 1, wherein the indicated resources include a priority parameter.

8. A wireless transmit / receive unit (WTRU), the WTRU comprising: a transceiver coupled to a processor, the transceiver and the processor being configured to receive one or more physical downlink shared channels (PDSCHs) in a first channel occupancy time (COT); the transceiver and the processor are further configured to: receive one or more PDSCHs in a second COT, and receive a physical downlink control channel (PDCCH) with control information in the second COT; the transceiver and the processor are configured to: aggregate hybrid automatic repeat request (HARQ) feedback for the one or more PDSCHs of the first COT and the one or more PDSCHs of the second COT based on the control information, and transmit the aggregated HARQ feedback in a physical uplink control channel (PUCCH) of the second COT based on resources indicated in the control information.

9. The WTRU according to claim 8, wherein the transceiver and the processor are further configured to perform listen-before-talk (LBT) before transmitting the aggregated HARQ feedback in the PUCCH of the second COT.

10. The WTRU of claim 9 wherein the transceiver and the processor are further configured to: decoding the one or more PDSCHs of the first COT and the one or more PDSCHs of the second COT, and It is determined that each PDSCH of each COT requires HARQ feedback.

11. The WTRU of claim 10, wherein the control information comprises an enhanced downlink assignment indicator (EDAI) indicating a group or time in which to aggregate HARQ feedback.

12. The WTRU of claim 11, wherein the transceiver and the processor are further configured to determine to aggregate the first PDSCH and the second PDSCH based on the EDAI.

13. The WTRU of claim 8, wherein the indicated resources are exclusive or non-exclusive.

14. The WTRU of claim 8, wherein the indicated resources include a priority parameter.

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