Method, apparatus, and system for system access in an unlicensed spectrum

Abstract

To provide a method, a device, and a system for a system access in unlicensed spectrum that can be implemented in a V2X device, a drone, a wearable device, an autonomous, or a semi-autonomous vehicle, a robotic device / vehicle, an automobile, an IoT gear, any device that moves, a wireless transmit / receive unit (WTRU) or other communication devices, and can be used in a communication network.SOLUTION: A method in a communication system includes receiving, by a wireless transmit / receive unit (WTRU), a channel transmission trigger (CTT) in a downlink message, selecting a type of listen-before-talk (LBT) configuration to be performed on the basis of the received CTT, determining whether a channel is available for transmission according to the selected type of LBT configuration, and transmitting data or control information on the channel, provided that the channel is available for transmission.SELECTED DRAWING: Figure 20

Description

Technical Field

[0001] Generally, it relates to wireless communication, for example, methods, apparatuses, and systems for system access in unlicensed spectrum.

Background Art

[0002] Cross - reference to Related Applications This application claims priority based on U.S. Provisional Patent Application No. 62 / 686943, filed on June 19, 2018, U.S. Provisional Patent Application No. 62 / 715315, filed on August 7, 2018, and U.S. Provisional Patent Application No. 62 / 735446, filed on September 24, 2018, each of which is incorporated herein by reference in its entirety.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Provide methods, apparatuses, and systems for system access in unlicensed spectrum.

Means for Solving the Problems

[0004] The disclosed embodiments include methods, apparatuses, and systems for using channels as described herein. In one representative method, a WTRU can receive a channel transmission trigger (CTT) in a downlink message and, based on the CTT, can select a type of listen before talk (LBT) configuration to be executed. The WTRU can further determine whether the channel is available for transmission according to the selected type of LBT configuration and, if the channel is available for transmission, can transmit data or control information on the channel.

[0005] A more detailed understanding can be obtained from the following detailed description given by way of example, in conjunction with the drawings attached to this specification. The figures in the description are examples. Therefore, the figures and the detailed description should not be regarded as limiting, and other equally effective examples are possible and may exist. Further, like reference numerals in the figures indicate like elements.

Advantages of the Invention

[0006] Providing a method, apparatus, and system for system access in an unlicensed spectrum

Brief Description of the Drawings

[0007]

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Mode for Carrying Out the Invention

[0008] -Exemplary network for implementing the embodiments- The various embodiments can be implemented in V2X devices, drones, wearable devices, autonomous or semi-autonomous vehicles, robotic devices / vehicles, automobiles, IoT gear, any moving device, or WTRUs or other communication devices, and in turn, they can be used in a communication network. The following sections provide an explanation of some exemplary WTRUs and / or other communication devices, and the networks into which they can be incorporated.

[0009] FIG. 1A is a diagram illustrating an exemplary communication system 100 that can implement one or more of the disclosed embodiments. The communication system 100 can be a multi-connectivity system that provides content such as voice, data, video, messaging, broadcast, etc. to a plurality of wireless users. The communication system 100 can enable a plurality of wireless users to access such content through sharing of system resources including wireless bandwidth. For example, the communication system 100 can utilize 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-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multicarrier (FBMC).

[0010] As shown in Figure 1A, the communication system 100 can include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a CN 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d can be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, which may also be referred to as "stations" and / or "STAs," can be configured to transmit and / or receive wireless signals and can include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular telephones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain scenarios), home appliances, and devices operating on commercial and / or industrial wireless networks. Any of the WTRUs 102a, 102b, 102c, 102d may alternatively be referred to as a UE.

[0011] The communication system 100 can also include base station 114a and / or base station 114b. Each of base stations 114a, 114b can be any type of device configured to wirelessly interface with at least one of WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as CN106 / 115, Internet 110, and / or other network 112. By way of example, base stations 114a, 114b can be a base transceiver station (BTS), Node B, evolved Node B (eNB), home Node B (HNB), home eNode B (HeNB), gNB, NR Node B, site controller, access point (AP), and wireless router, among others. Although base stations 114a, 114b are each depicted as a single element, it will be understood that base stations 114a, 114b can include any number of interconnected base stations and / or network elements.

[0012] Base station 114a can be part of RAN104 / 113, which can also include other base stations and / or network elements (not shown) such as base station controllers (BSCs), radio network controllers (RNCs), relay nodes, etc. Base station 114a and / or base station 114b can be configured to transmit and / or receive radio signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies can be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell can provide coverage for wireless services in a specific geographic area that can be relatively constant or can change over time. A cell can further be divided into cell sectors. For example, a cell associated with base station 114a can be divided into three sectors. Thus, in one embodiment, base station 114a can include three transceivers, i.e., one for each sector of the cell. In an embodiment, base station 114a can utilize multiple-input multiple-output (MIMO) technology and can utilize multiple transceivers for each sector of the cell. For example, beamforming can be used to transmit and / or receive signals in a desired spatial direction.

[0013] Base stations 114a, 114b can communicate with one or more of WTRUs 102a, 102b, 102c, 102d over air interface 116, which can be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). Air interface 116 can be established using any suitable radio access technology (RAT).

[0014] More specifically, as mentioned above, the communication system 100 can be a multi-connection system and can utilize one or more channel access methods such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, the base station 114a within the RAN 104 / 113 and the WTRUs 102a, 102b, 102c can establish the air interface 116 using wideband CDMA (WCDMA) and implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA). WCDMA can include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA can include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0015] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can establish the air interface 116 using Long-Term Evolution (LTE), and / or LTE-Advanced (LTE-A), and / or LTE-Advanced Pro (LTE-A Pro) and implement radio technologies such as Evolved UMTS Terrestrial Radio Access (E-UTRA).

[0016] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can establish the air interface 116 using New Radio (NR) and implement radio technologies such as NR radio access.

[0017] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c can implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c can implement LTE radio access and NR radio access together, for example, using the dual connectivity (DC) principle. Accordingly, the air interfaces utilized by the WTRUs 102a, 102b, 102c can be characterized by transmissions from multiple types of radio access technologies and / or multiple types of base stations (e.g., in particular, eNB 160 and gNB 180).

[0018] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c can implement wireless technologies such as IEEE 802.11 (i.e., wireless fidelity (WiFi)), IEEE 802.16 (i.e., worldwide interoperability for microwave access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, interim standard 2000 (IS-2000), interim standard 95 (IS-95), interim standard 856 (IS-856), global system for mobile communications (GSM), high speed data rate for GSM evolution (EDGE), and GSM EDGE (GERAN).

[0019] The base station 114b in Fig. 1A can be, for example, a wireless router, a home node B, a home eNB, or an access point, and can utilize any suitable RAT to facilitate wireless connectivity in a localized area such as an office, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., used by a drone), and a roadway. In one embodiment, the base station 114b and the WTRUs 102c, 102d can implement a wireless technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d can implement a wireless technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d can utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a pico cell or a femto cell. As shown in Fig. 1A, the base station 114b can have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 via the CN 106 / 115.

[0020] RAN 104 / 113 can communicate with CN 106 / 115, which can be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRUs 102a, 102b, 102c, 102d. The data can have various Quality of Service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. CN 106 / 115 can provide call control, billing services, mobile location-based services, prepaid originating calls, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in Figure 1A, it will be understood that RAN 104 / 113 and / or CN 106 / 115 can communicate directly or indirectly with other RANs that utilize the same or a different Radio Access Technology (RAT) as RAN 104 / 113. For example, in addition to being connected to RAN 104 / 113 which may be utilizing New Radio (NR) wireless technology, CN 106 / 115 can also communicate with another RAN (not shown) that utilizes GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi wireless technology.

[0021] CN106 / 115 can also serve as a gateway for WTRU102a, 102b, 102c, 102d to access the PSTN108, the Internet 110, and / or other networks 112. The PSTN108 can include a circuit-switched telephone network that provides basic telephone service (POTS). The Internet 110 can include a worldwide system of interconnected computer networks and devices that use common communication protocols such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) within the TCP / IP Internet protocol suite. The network 112 can include wired and / or wireless communication networks that are owned and / or operated by other service providers. For example, the network 112 can include another CN connected to one or more RANs that can utilize the same RAT or a different RAT as the RAN104 / 113.

[0022] Some or all of the WTRU102a, 102b, 102c, 102d within the communication system 100 can include a multimode function (e.g., the WTRU102a, 102b, 102c, 102d can include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU102c shown in Figure 1A can be configured to communicate with a base station 114a that can utilize cellular-based wireless technology and with a base station 114b that can utilize IEEE802 wireless technology.

[0023] Figure 1B is a system diagram illustrating an exemplary WTRU 102. As shown in Figure 1B, the WTRU 102 can include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripheral devices 138. It will be understood that the WTRU 102 can include any sub-combination of the above elements while maintaining consistency with the embodiments.

[0024] The processor 118 can be, for example, a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors cooperating 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), and a state machine. The processor 118 can perform signal encoding, 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 can be coupled to the transceiver 120, and the transceiver 120 can be coupled to the transmit / receive element 122. Although Figure 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0025] The transmit / receive element 122 can be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 can be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 can be a radiator / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 can be configured to transmit and / or receive both RF signals and optical signals. It will be understood that the transmit / receive element 122 can be configured to transmit and / or receive any combination of wireless signals.

[0026] In FIG. 1B, the transmit / receive element 122 is depicted as a single element, but the WTRU 102 can include any number of transmit / receive elements 122. More specifically, the WTRU 102 can utilize MIMO technology. Thus, in one embodiment, the WTRU 102 can include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0027] The transceiver 120 can be configured to modulate the signals that will be transmitted by the transmit / receive element 122 and demodulate the signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 can have a multi-mode function. Thus, the transceiver 120 can include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.

[0028] The processor 118 of the WTRU 102 can be coupled to and receive user input data from a speaker / microphone 124, keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 can also output user data to the speaker / microphone 124, keypad 126, and / or the display / touchpad 128. In addition, the processor 118 can obtain information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 can include a random access memory (RAM), read only memory (ROM), hard disk, or any other type of memory storage device. The removable memory 132 can include, for example, a subscriber identity module (SIM) card, a memory stick, and a secure digital (SD) memory card. In other embodiments, the processor 118 can obtain information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0029] The processor 118 can receive power from a power source 134 and can be configured to distribute power to and / or control power to other components within the WTRU 102. The power source 134 can be any suitable device for powering the WTRU 102. For example, the power source 134 can include one or more dry cells (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), a solar cell, and a fuel cell.

[0030] Processor 118 can also be coupled to a GPS chipset 136, which can be configured to provide location information (e.g., longitude and latitude) regarding the current location of WTRU 102. In addition to, or instead of, information from the GPS chipset 136, WTRU 102 can receive location information on air interface 116 from a base station (e.g., base stations 114a, 114b), and / or can determine its location based on the timing of signals received from two or more nearby base stations. It will be understood that WTRU 102 can obtain location information using any suitable location determination method while maintaining consistency with the embodiments.

[0031] Processor 118 can further be coupled to other peripheral devices 138, which can include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripheral devices 138 can include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photos and / or videos), a Universal Serial Bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a Frequency Modulation (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, and an activity tracker, among others. The peripheral devices 138 can include one or more sensors, which can be one or more of a gyroscope, an accelerometer, a Hall effect sensor, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0032] The processor 118 of the WTRU 102 can operably communicate with various peripheral devices 138, including, for example, one or more accelerometers, one or more gyroscopes, a USB port, other communication interfaces / ports, a display, and / or other visual / audible indicators, to implement the exemplary embodiments disclosed herein.

[0033] The WTRU 102 can include a full-duplex radio in which some or all of the transmission and reception of signals associated with a particular subframe (for both, e.g., UL (for transmission) and DL (for reception)) can be parallel and / or simultaneous. The full-duplex radio can include an interference management unit to reduce and / or substantially eliminate self-interference, either via hardware (e.g., a choke) or via signal processing through a processor (e.g., a separate processor (not shown) or the processor 118). In embodiments, the WTRU 102 can include a half-duplex radio for some or all of the transmission and reception of signals associated with a particular subframe (for either, e.g., UL (for transmission) or DL (for reception)).

[0034] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106, in accordance with an embodiment. As mentioned above, the RAN 104 can communicate with the WTRU 102a, 102b, 102c over the air interface 116, using the E-UTRA radio technology. The RAN 104 can also communicate with the CN 106.

[0035] RAN 104 can include eNBs 160a, 160b, 160c, although it will be understood that RAN 104 can include any number of eNBs while maintaining consistency with the embodiments. eNBs 160a, 160b, 160c can each include one or more transceivers for communicating with WTRUs 102a, 102b, 102c over air interface 116. In one embodiment, eNBs 160a, 160b, 160c can implement MIMO technology. Thus, eNB 160a, for example, can transmit wireless signals to and / or receive wireless signals from WTRU 102a using multiple antennas.

[0036] Each of eNBs 160a, 160b, 160c can be associated with a particular cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, and user scheduling in the UL and / or DL, etc. As shown in Figure 1C, eNBs 160a, 160b, 160c can communicate with each other over the X2 interface.

[0037] CN 106 shown in Figure 1C can include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (or PGW) 166. Each of the above elements is depicted as part of CN 106, although it will be understood that any of these elements can be owned and / or operated by an entity different from the CN operator.

[0038] The MME 162 can be connected to each of the eNBs 160a, 160b, and 160c within the RAN 104 via the S1 interface and can serve as a control node. For example, the MME 162 can be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, and selecting a specific serving gateway during the initial attach of the WTRUs 102a, 102b, 102c. The MME 162 can provide control plane functions for exchanges between the RAN 104 and other RANs (not shown) that utilize other radio technologies such as GSM and / or WCDMA.

[0039] The SGW 164 can be connected to each of the eNBs 160a, 160b, and 160c within the RAN 104 via the S1 interface. The SGW 164 can generally route and transfer user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 can perform other functions such as anchoring the user plane during handover between eNBs, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0040] The SGW 164 can be connected to the PGW 166, which can provide access to a packet switched network, such as the Internet 110, to the WTRUs 102a, 102b, 102c and facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0041] CN106 can facilitate communication with other networks. For example, CN106 can provide access to a circuit-switched network, such as PSTN108, to WTRUs 102a, 102b, and 102c to facilitate communication between WTRUs 102a, 102b, and 102c and conventional landline communication devices. For example, CN106 can include, or communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN106 and PSTN108. Additionally, CN106 can provide access to other network 112 to WTRUs 102a, 102b, and 102c, where other network 112 can include other wired and / or wireless networks owned and / or operated by other service providers.

[0042] In FIGS. 1A - 1D, the WTRU is described as a wireless terminal, but in some representative embodiments, it is contemplated that such a terminal can use (e.g., temporarily or permanently) a wired communication interface with a communication network.

[0043] In a representative embodiment, other network 112 can be a WLAN.

[0044] A WLAN in infrastructure basic service set (BSS) mode can have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP can have an access or interface to a distribution system (DS) or another type of wired / wireless network that conveys traffic within and / or outside the BSS. Traffic destined for an STA originating from outside the BSS can arrive through the AP and be delivered to the STA. Traffic transmitted from an STA to a destination outside the BSS can be sent to the AP for delivery to their respective destinations. Traffic between STAs within the BSS can be transmitted through the AP. For example, the source STA can send the traffic to the AP, and the AP can deliver the traffic to the destination STA. Traffic between STAs within the BSS can be considered peer-to-peer traffic and / or sometimes be called peer-to-peer traffic. Peer-to-peer traffic can be transmitted (e.g., directly) between the source STA and the destination STA using direct link setup (DLS). In one representative embodiment, the DLS can use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using independent BSS (IBSS) mode may not have an AP, and STAs within the IBSS or using the IBSS (e.g., all of the STAs) can communicate directly with each other. Communication in IBSS mode is sometimes referred to herein as "ad hoc" mode communication.

[0045] When operating in 802.11ac infrastructure mode or a similar mode of operation, the AP can transmit beacons on a fixed channel such as the primary channel. The primary channel can be of a fixed width (e.g., 20 MHz bandwidth) or a width dynamically set via signaling. The primary channel can be the operating channel of the BSS and can be used by the STA to establish a connection with the AP. In one representative embodiment, for example, in an 802.11 system, Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) can be implemented. In the case of CSMA / CA, STAs including the AP (e.g., any STA) can sense the primary channel. If the primary channel is sensed / detected by a particular STA and / or determined to be busy, the particular STA can back off. Within a given BSS, at any given time, one STA (e.g., only one STA) can transmit.

[0046] A High Throughput (HT) STA can use a 40 MHz wide channel for communication, for example, by combining the primary 20 MHz channel with adjacent or non - adjacent 20 MHz channels to form a 40 MHz wide channel.

[0047] Very High Throughput (VHT) STAs can support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. 40 MHz and / or 80 MHz channels can be formed by combining consecutive 20 MHz channels. A 160 MHz channel can be formed by combining eight consecutive 20 MHz channels, or by combining two non - consecutive 80 MHz channels, which may be referred to as the 80 + 80 configuration. In the case of the 80 + 80 configuration, data can pass through a segment parser that can split the data into two streams after channel encoding. For each stream separately, an Inverse Fast Fourier Transform (IFFT) process and time - domain processing can be performed. The streams can be mapped onto two 80 MHz channels and the data can be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80 + 80 configuration can be reversed and the combined data can be transmitted to the Media Access Control (MAC).

[0048] Operation in sub-1 GHz mode is supported by 802.11af and 802.11ah. Channel operating bandwidth and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV white space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to an exemplary embodiment, 802.11ah can support meter type control / machine type communication, such as MTC devices in a macro coverage area. MTC devices can have limited functionality, including certain functions, such as support for a certain bandwidth and / or limited bandwidth (e.g., only their support). MTC devices can include a battery having a battery life above a threshold (e.g., to maintain a very long battery life).

[0049] A WLAN system that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, includes channels that can be designated as primary channels. The primary channel can have a bandwidth equal to the maximum common operating bandwidth supported by all STAs within a BSS. The bandwidth of the primary channel can be set and / or restricted by the STA that supports the minimum bandwidth operation mode among all STAs operating within the BSS. In the example of 802.11ah, even if the AP and other STAs within the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operation modes, for an STA (e.g., an MTC type device) that supports (e.g., only supports) the 1MHz mode, the primary channel can be 1MHz wide. Carrier sensing and / or network allocation vector (NAV) setting can depend on the status of the primary channel. For example, if the primary channel is busy because an STA (that only supports the 1MHz operation mode) is transmitting to the AP, even if most of the available frequency band remains idle and can be available, the entire available frequency band can be regarded as busy.

[0050] In the United States, the available frequency band that can be used by 802.11ah is from 902MHz to 928MHz. In South Korea, the available frequency band is from 917.5MHz to 923.5MHz. In Japan, the available frequency band is from 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is from 6MHz to 26MHz, depending on national regulations.

[0051] Figure 1D is a system diagram showing RAN 113 and CN 115 according to an embodiment. As mentioned above, RAN 113 can communicate with WTRUs 102a, 102b, 102c over air interface 116 using NR radio technology. RAN 113 can also communicate with CN 115.

[0052] RAN 113 can include gNBs 180a, 180b, 180c, although it will be understood that RAN 113 can include any number of gNBs while maintaining consistency with the embodiment. Each of gNBs 180a, 180b, 180c can include one or more transceivers for communicating with WTRUs 102a, 102b, 102c over air interface 116. In one embodiment, gNBs 180a, 180b, 180c can implement MIMO technology. For example, WTRUs 102a, 108b can transmit signals to and / or receive signals from gNBs 180a, 180b, 180c using beamforming. Thus, gNB 180a can transmit wireless signals to and / or receive wireless signals from WTRU 102a, for example, using multiple antennas. In an embodiment, gNBs 180a, 180b, 180c can implement carrier aggregation technology. For example, gNB 180a can transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers can be on unlicensed spectrum, while the remaining component carriers can be on licensed spectrum. In an embodiment, gNBs 180a, 180b, 180c can implement multi-site coordinated (CoMP) technology. For example, WTRU 102a can receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0053] WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c using transmissions associated with scalable numerology. For example, the OFDM symbol interval, and / or the OFDM sub-carrier interval can vary for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c using sub-frames or transmission time intervals (TTIs) of various or scalable lengths (e.g., including various numbers of OFDM symbols and / or lasting for various lengths of absolute time).

[0054] gNBs 180a, 180b, and 180c can be configured to communicate with WTRUs 102a, 102b, and 102c in a stand-alone configuration and / or a non-stand-alone configuration. In a stand-alone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c without accessing other RANs (such as eNBs 160a, 160b, and 160c). In a stand-alone configuration, WTRUs 102a, 102b, and 102c can utilize one or more of gNBs 180a, 180b, and 180c as mobility anchor points. In a stand-alone configuration, WTRUs 102a, 102b, and 102c can communicate with gNBs 180a, 180b, and 180c using signals within an unlicensed band. In a non-stand-alone configuration, WTRUs 102a, 102b, and 102c can communicate with / connect to gNBs 180a, 180b, and 180c while also communicating with / connecting to another RAN such as eNBs 160a, 160b, and 160c. For example, WTRUs 102a, 102b, and 102c can implement the DC principle to communicate with one or more gNBs 180a, 180b, and 180c and one or more eNBs 160a, 160b, and 160c substantially simultaneously. In a non-stand-alone configuration, eNBs 160a, 160b, and 160c can serve as mobility anchors for WTRUs 102a, 102b, and 102c, and gNBs 180a, 180b, and 180c can provide additional coverage and / or throughput to serve WTRUs 102a, 102b, and 102c.

[0055] Each of gNBs 180a, 180b, and 180c can be associated with a specific cell (not shown) and is configured to handle wireless resource management decisions, handover decisions, user scheduling in UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPFs) 184a, 184b, and routing of control plane information to access and mobility management functions (AMFs) 182a, 182b. As shown in Figure 1D, gNBs 180a, 180b, and 180c can communicate with each other over the Xn interface.

[0056] CN 115 shown in Figure 1D can include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possibly data networks (DNs) 185a, 185b. Although each of the above elements is depicted as part of CN 115, it will be understood that any of these elements can be owned and / or operated by entities different from the CN operator.

[0057] AMF 182a and 182b can be connected to one or more of gNBs 180a, 180b, and 180c in RAN 113 via the N2 interface and can serve as control nodes. For example, AMF 182a and 182b can authenticate users of WTRUs 102a, 102b, and 102c, support network slicing (e.g., handle different protocol data unit (PDU) sessions with different requirements), select specific SMFs 183a and 183b, manage the registration area, terminate NAS signaling, and perform mobility management, etc. Network slicing can be used by AMF 182a and 182b to customize the CN support for WTRUs 102a, 102b, and 102c based on the type of service utilized by WTRUs 102a, 102b, and 102c. For example, different network slices can be established for different use cases such as services relying on ultra-reliable low-latency (URLLC) access, services relying on high-speed large-capacity mobile broadband (eMBB) access, and / or services for machine type communication (MTC) access. AMF 182a and 182b can provide control plane functions for exchanges between RAN 113 and other RANs (not shown) that utilize other radio technologies such as non-3GPP access technologies like LTE, LTE-A, LTE-A Pro, and / or WiFi.

[0058] SMF183a and 183b can be connected to AMF182a and 182b in CN115 via the N11 interface. SMF183a and 183b can also be connected to UPF184a and 184b in CN115 via the N4 interface. SMF183a and 183b can select and control UPF184a and 184b and configure the routing of traffic through UPF184a and 184b. SMF183a and 183b can perform other functions such as managing and allocating UE (or WTRU) IP addresses, managing PDU sessions, implementing policies and controlling QoS, and providing downlink data notifications. The PDU session type can be IP-based, non-IP-based, Ethernet-based, etc.

[0059] UPF184a and 184b can be connected to one or more of gNB180a, 180b, and 180c in RAN113 via the N3 interface, and they can provide access to a packet-switched network such as the Internet 110 to WTRU102a, 102b, and 102c to facilitate communication between WTRU102a, 102b, and 102c and IP-compatible devices. UPF184a and 184b can perform other functions such as routing and forwarding packets, implementing user plane policies, supporting multi-homing PDU sessions, processing user plane QoS, buffering downlink packets, and providing mobility anchoring.

[0060] CN115 can facilitate communication with other networks. For example, CN115 can include, or communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN115 and the PSTN108. In addition, CN115 can provide access to other networks 112 to the WTRU102a, 102b, 102c, where the other networks 112 can include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRU102a, 102b, 102c can be connected to the local data network (DN) 185a, 185b through the UPF184a, 184b via an N3 interface to the UPF184a, 184b, and an N6 interface between the UPF184a, 184b and the DN185a, 185b.

[0061] In view of FIGS. 1A-1D, and the corresponding descriptions of FIGS. 1A-1D, one or more of the functions described herein with respect to one or more of the WTRU102a-d, base stations 114a-b, eNBs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other devices described herein can be performed by one or more emulation devices (not shown). An emulation device can be one or more devices configured to emulate one or more or all of the functions described herein. For example, an emulation device can be used to test other devices and / or to simulate network and / or WTRU functionality.

[0062] An emulation device can be designed to perform one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more emulation devices can execute one or more or all functions while being fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices within the communication network. One or more emulation devices can execute one or more or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. An emulation device can be directly coupled to another device for the purpose of conducting a test and / or can execute the test using over-the-air wireless communication.

[0063] One or more emulation devices can execute one or more functions including all functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, an emulation device can be utilized in a test scenario in a test laboratory and / or in a non-deployed (e.g., test) wired and / or wireless communication network to perform tests of one or more components. One or more emulation devices can be test equipment. The emulation device can use direct RF coupling and / or wireless communication via an RF circuit (which can include, for example, one or more antennas) to transmit and / or receive data.

[0064] -Typical Unlicensed Operations- Operation in an unlicensed frequency band may be subject to some restrictions on transmit power control (TPC), RF output power, and / or power density, given, for example, by the average equivalent isotropically radiated power (EIRP) and / or average EIRP density at the highest power level. Operation in an unlicensed frequency band may also be subject to requirements and / or restrictions on out-of-band emissions of the transmitter. The requirements and / or restrictions can be specific to a particular frequency band and / or geographic location.

[0065] Operation may also be subject to requirements / restrictions on the nominal channel bandwidth (NCB) and / or occupied channel bandwidth (OCB), which can be defined for the unlicensed spectrum in the 5 GHz region. The NCB (e.g., the widest frequency band including guard bands assigned to a single channel) can, for example, always be at least 5 MHz. The OCB (e.g., the bandwidth containing 99% of the power of the signal) can be in the range between 80% and 100% of the declared NCB. During an established communication, a device can be permitted to operate (e.g., temporarily operate) in a mode where it can reduce its OCB to as low as, for example, 40% of its NCB, having a minimum bandwidth (e.g., 4 MHz).

[0066] Channel access in an unlicensed frequency band can use a listen before talk (LBT) mechanism. LBT may be mandatory regardless of whether the channel is occupied (e.g., generally mandatory). In one representative embodiment, the channel can be a continuous portion of the frequency band, and in other representative embodiments, the channel can be a plurality of non - continuous portions consisting of one or more frequency bands. In the context of an unlicensed frequency band, the channel can be a spectrum resource that is available for communication and is determined by the LBT mechanism / operation. The channel can include a set of resources on which a single LBT procedure can be performed for a WTRU to acquire an occupied channel bandwidth (e.g., LBT bandwidth).

[0067] For a frame - based system, LBT can be characterized by a clear channel assessment (CCA) time (e.g., within a range of about 20 μs), a channel occupancy time (COT) (e.g., minimum 1 ms, maximum 10 ms), an idle period (e.g., minimum 5% of COT), a fixed frame period (e.g., equal to COT + idle period), a short control signaling transmission time (e.g., maximum 5% duty cycle within a 50 ms observation period), and / or a CAA energy detection threshold.

[0068] For a load - based system (e.g., where the transmit / receive structure may not be fixed in time), LBT can be characterized, for example, by a number N corresponding to the number of empty idle slots in an extended CCA instead of a fixed frame period. N can be selected (e.g., randomly selected) within a range.

[0069] The deployment scenario can include different variations of carrier aggregation (CA), which can include different stand-alone NR-based operations, different variations of dual connectivity operations, e.g., e.g., EN-DC where at least one carrier operates according to the LTE radio access technology (RAT), or e.g., NR-DC where at least two sets of one or more carriers operate according to the NR RAT, and / or e.g., different combinations of zero or more carriers of each of the LTE and NR RATs, probably also including.

[0070] For example, for LTE, any combination of the following functionalities can be implemented in a license-assisted access (LAA) system.

[0071] (1) Define LBT (CCA), which can be applied or should be applied by the device as a mechanism by which the LBT procedure (sometimes called the LBT operation) can be used by the device to apply the CCA check before using the channel. CCA can determine the presence or absence of other signals on the channel using at least energy detection to determine whether the channel is occupied or empty, respectively. Certain regulations and / or operations may mandate the use of LBT in unlicensed frequency bands. Apart from regulatory / operational requirements, carrier sensing via LBT is one way for fair sharing of the unlicensed spectrum and can be an essential feature for fair and friendly operation in the unlicensed spectrum, e.g., in a single global solution framework.

[0072] (2) Discontinuous transmission on a carrier with a limited maximum transmission duration (in unlicensed spectrum, channel availability cannot be guaranteed (e.g., it cannot always be guaranteed). For example, in some regions (such as in Europe and Japan), continuous transmission may be prohibited and / or there may be restrictions on the maximum duration of transmission bursts in unlicensed spectrum. Discontinuous transmission with a limited maximum transmission duration may be required for LAA and / or may be an appropriate function).

[0073] (3) Carrier selection (e.g., since there is a wide available bandwidth in unlicensed spectrum, carrier selection may be required for LAA nodes and / or may be appropriate to select a carrier with low interference (e.g., below a threshold level) and such a carrier for achieving good coexistence with other unlicensed spectrum deployments).

[0074] (4) TPC (e.g., TPC may be a regulatory requirement and / or in some regions it may be appropriate that the transmitting device can reduce the transmission power by a ratio of 3 dB or 6 dB compared to the maximum nominal transmission power and / or should be reduced).

[0075] (5) Radio Resource Management (RRM) measurements (e.g., including cell identification can enable mobility between SCell and / or robust operation in unlicensed frequency bands).

[0076] (6) Channel State Information (CSI) measurements (including, for example, channels and interference).

[0077] A WTRU operating on an unlicensed carrier can support frequency / time estimation and synchronization, for example, to enable RRM measurements for normal reception of information on the unlicensed frequency band.

[0078] In one representative embodiment, the gNB can perform a certain LBT study and trigger one or more WTRUs to indicate one or more next PRACH opportunities. The WTRU can determine the LBT configuration from the trigger content or trigger reception time related to the corresponding uplink transmission.

[0079] In one representative embodiment, the WTRU can explicitly and / or implicitly monitor (monitor) the PRACH resource trigger signal, for example, according to a pre-configured pattern. The trigger signal can indicate the PRACH configuration / resource.

[0080] In one representative embodiment, for example, if the WTRU is configured to use one or more switching points for the COT obtained from the gNB, via the gNB, or by the gNB, and / or is conveyed (explicitly conveyed to indicate it, or implicitly conveyed based on the situation of the random access (RA) procedure) to indicate it, the WTRU can skip and / or apply different LBT configurations before transmitting message 3 (msg3).

[0081]

[0082] In one representative embodiment, the WTRU can attempt to transmit / receive messages 1, 2, 3, and / or 4 (msg1 / 2 / 3 / 4) by performing LBT on multiple resources, perhaps on different sub-bands, BWPs, cells, and / or channels according to independent LBT (e.g., independent LBT operations).

[0083] ​In one representative embodiment, the WTRU can maintain a preamble / SR attempt counter that can be incremented each time the MAC instructs the PHY to transmit a preamble / SR, regardless of the result of the LBT, or each time a preamble / SR transmission attempt fails the LBT. The WTRU can reset the counter when switching to a different channel and / or when a related timer expires.

[0084] In one representative embodiment, the WTRU can switch to a different LBT sub-band, BWP, cell, and / or channel when the preamble / SR attempt counter exceeds a certain threshold. The WTRU can further (1) initiate a random access procedure, (2) retransmit a preamble or SR, and / or (3) report a radio link problem to a higher layer.

[0085] In one representative embodiment, the WTRU can apply a backoff value determined by the WTRU according to a preconfigured and / or transmitted value according to the channel occupancy state.

[0086] In one representative embodiment, the WTRU can apply different LBT windows and / or configurations according to the RA priority.

[0087] In one representative embodiment, the scheduling request (SR) procedure in New Radio Unlicensed (NR-U) can include any of a triggered physical uplink control channel (PUCCH) transmission, SR retransmission, SR triggering and / or cancellation, and / or SR prohibition timer adjustment.

[0088] In one representative embodiment, the WTRU can implement a method, procedure, operation, apparatus, and / or system for determining PUCCH resource availability in accordance with the reception of a PUCCH resource trigger signal. The gNB can perform a certain LBT consideration and trigger one or more WTRUs to indicate one or more next PUCCH opportunities.

[0089] In one representative embodiment, depending on the channel occupancy state or whether an LBT (e.g., LBT operation) failure has occurred for one or more PUSCH resources provided after transmitting an SR, the WTRU can implement a method, procedure, operation, apparatus, and / or system for adjusting the SR prohibition timer of the pending SR.

[0090] In one representative embodiment, a WTRU that can support and / or use, for example, multiple active bandwidth parts (BWPs) can implement a method, procedure, operation, apparatus, and / or system for triggering additional SRs (e.g., on different subbands and / or BWPs under certain conditions).

[0091] In one representative embodiment, when transmitting a PDU that includes or contains a buffer status report (BSR) media access control control element (MAC CE) and / or upon indication (e.g., from the PHY (e.g., physical layer)) that the LBT operation for the corresponding PUSCH transmission was successful, the WTRU can implement a method, procedure, operation, apparatus, and / or system for canceling the pending SR and / or the pending BSR.

[0092] In one representative embodiment, a method, procedure, operation, apparatus, and / or system for a triggered PRACH transmission (e.g., regarding when and / or how to perform the LBT operation when triggered for PRACH) can be implemented.

[0093] In certain representative embodiments, for example, when the SSB is sent opportunistically, a method, procedure, operation, apparatus, and / or system for performing a beam indication can be implemented.

[0094] In certain representative embodiments, for example, a method, procedure, operation, apparatus, and / or system for a modified LBT (e.g., modified LBT operation) to enable WTRU multiplexing of PRACH and other UL channels can be implemented.

[0095] In certain representative embodiments, for example, a method, procedure, operation, apparatus, and / or system for enabling interleaved PRACH and PUSCH (e.g., for multi-step RACH, e.g., 2-step RACH) can be implemented.

[0096] In certain representative embodiments, for example, a method, procedure, operation, apparatus, and / or system for a conditionally configured grant and its triggering can be implemented.

[0097] In certain representative embodiments, the WTRU can be configured to apply a differentiated LBT configuration to preamble transmission when starting or after starting a high-priority random access procedure.

[0098] In certain representative embodiments, the WTRU can be configured to apply a certain LBT configuration to SR transmission, whereby the LBT configuration can be selected according to a selected SR configuration and / or the logical channel that triggered the pending SR.

[0099] - Representative Operations in 3GPP Release 15 (R15) New Radio (NR)- In NR, a WTRU can operate using a bandwidth part (BWP) within a carrier. The WTRU can access a cell using an initial BWP. Thereafter, the WTRU can be configured to use a set of BWPs to continue operation. In one representative embodiment, at any given instant, the WTRU can have one active BWP. In other representative embodiments, the WTRU can have one or more active BWPs. Each BWP can be configured to use a set of core sets in which the WTRU can blindly decode physical downlink control channel (PDCCH) candidates, inter alia, for scheduling.

[0100] The NR system can support and / or implement variable transmission duration and / or feedback timing. With variable transmission duration, physical downlink shared channel (PDSCH) transmission and / or physical uplink shared channel (PUSCH) transmission can occupy a continuous subset of symbols of a slot. With variable feedback timing, downlink control information (DCI) for downlink (DL) allocation can include an indication of the feedback timing for the WTRU (e.g., by indicating a specific PUCCH resource).

[0101] The NR system can support and / or implement different types of physical uplink control channel (PUCCH) resources (e.g., two or more types of PUCCH resources), e.g., short PUCCH and / or long PUCCH. The short PUCCH can be transmitted using one or two OFDM symbols, and the long PUCCH can use up to 14 OFDM symbols. Each PUCCH type can have multiple formats that can depend, e.g., on the corresponding payload type and / or size.

[0102] In NR, the RA procedure can be prioritized, for example, according to the RA start type. The prioritized RA (e.g., RACH) procedure can use a differentiated backoff value and / or power ramping value configured by the network (e.g., a network entity).

[0103] The NR WTRU can be configured to use multiple SR configurations. The SR configuration can be a set of PUCCH resources having a certain periodicity. In one representative embodiment, radio resource control (RRC) can configure the logical channels (e.g., each logical channel) to use a single SR configuration.

[0104] In a cell to be beamformed (e.g., an NR licensed beamformed cell), the association between the beam (represented by SSB and / or CSI-RS) and the PRACH resource or preamble can be configured to assist the WTRU in indicating to the network (e.g., a network entity and / or gNB) which beam can be the best or is the best for the reception of, for example, RAR and / or further downlink signals. For example, consecutive SSBs can be mapped to consecutive PRACH occasions in the time domain. The synchronization signal (SS) burst can be a set of consecutive SSBs used to transmit synchronization signals. In the case of a beamformed NR-U cell, a subset of the beams within the SS burst may not be found due to LBT failure. The transmission timing of the missing SSB can be indicated by a timing offset and / or, for example, the missing SSB can be determined by the WTRU by assuming that it should be transmitted cyclically after the last SSB in the SS burst.

[0105] - Representative WTRU Operations in the Unlicensed Band for NR Release 16 (R16) In certain representative embodiments, methods, apparatuses, and systems for supporting operation in the unlicensed band for R16 operation, including initial access, RA, scheduling / HARQ, and / or mobility, can be implemented, along with coexistence operations / procedures with LTE-LAA and other incumbent RATs. For example, such embodiments can include NR-based LAA cells connected to an LTE anchor and / or an NR anchor cell, as well as NR-based cells operating stand-alone using unlicensed spectrum.

[0106] In certain representative embodiments, methods, apparatuses, and systems for supporting operation in the unlicensed band for RA can be implemented, including, for example, interlacing PRACH signals, such as to interlace PUSCH transmissions in eLAA, while meeting OCB requirements, including, for example, enhancements to the PRACH physical channel structure and / or RA procedures.

[0107] In certain representative embodiments, methods, apparatuses, and systems for supporting operation in the unlicensed band for RA for NR-U cells can be implemented in stand-alone mode and in LTE-NR deployment scenarios. For RA for NR-U cells, since preamble, RAR, msg3, and / or msg4 transmissions can follow LBT results, multi-step (e.g., 4-step) RA procedures may not even need to consider retransmissions and can use up to 4 independent LBT procedures before each transmission and / or as may be required. Using CCA and / or as may be required before applying a multi-step RA procedure to an NR-U cell can cause a delay (e.g., a significant delay), up to (e.g., until completion of the multi-step RA procedure).

[0108] In an NR license, a physical random access channel (PRACH) occasion can represent a system access opportunity on time - frequency resources provided by a network entity (e.g., gNB) where multiple WTRUs can start a simultaneous RA procedure on the same PRACH occasion when different preambles are selected. In NR - U, a PRACH occasion can represent a conditional system access opportunity that follows the LBT result. A single WTRU transmitting a preamble on a given PRACH occasion can block other WTRUs from transmitting a different preamble on the same channel and can affect the RACH capacity in an NR - U cell. For a WTRU in connected mode, transmitting an SR or uplink control information (UCI) on a PUCCH in NR - U can follow the LBT procedure and / or use the LBT procedure.

[0109] -Typical LBT impact on RA procedure- -Typical triggered PRACH opportunities- Figure 2 illustrates a representative RA procedure 200 that transmits a PRACH transmission (e.g., PRACH 220a and / or 220b) upon receiving a trigger signal 210 (e.g., a PRACH trigger signal 210).

[0110] Referring to FIG. 2, the RA procedure 200 can include a first WTRU 102a that may desire to initiate the RA procedure 230a. Thereafter, a second WTRU 102b may desire to initiate the RA procedure 230b. The channel may be busy (e.g., over the channel busy period 215), and / or the first WTRU 102a and the second WTRU 102b may wait for the PRACH trigger signal 210. For example, a network entity (e.g., gNB 180a) may transmit the PRACH trigger signal 210 (e.g., for broadcasting, multicasting, and / or unicasting) to indicate that the first WTRU 102a and the second WTRU 102b can transmit PRACH transmissions 220a and 220b, e.g., indicating that the channel is available (e.g., the channel is not busy and / or is no longer busy). While the channel is busy (e.g., during the channel busy period 215), gNB 180a cannot transmit the PRACH trigger signal 210. After the channel becomes available (e.g., after the channel busy period 215 ends and / or after gNB 180a determines that the channel is available and / or is idle), gNB 180a can transmit the PRACH trigger signal 210. The first WTRU 102a and the second WTRU 102b can monitor and receive the PRACH trigger 210. After receiving or in response to receiving the PRACH trigger signal 210, the first WTRU 102a can transmit the RA preamble transmission 220a to, for example, initiate the RA procedure for the WTRU 102a. After receiving or in response to receiving the PRACH trigger signal 210, the second WTRU 102b can similarly transmit the RA preamble transmission 220b to, for example, initiate the RA procedure for the WTRU 102b.

[0111] The WTRUs 102a, 102b are indicated and / or can be configured to use a PRACH resource on which the WTRU 102 can transmit a PRACH preamble (e.g., PRACH preamble transmission 220) (e.g., to start or initiate a RA procedure). The PRACH resource can include, inter alia, (1) a time resource (e.g., a set of symbols), (2) a frequency resource (e.g., a set of physical resource blocks (PRBs)), (3) one or more analog / digital / hybrid precoders (e.g., one or more transmission beams), (4) one or more cover codes or preambles (e.g., to enable orthogonal or non-orthogonal multiplexing), (5) one or more interleaving patterns (e.g., a subset of subcarriers or PRBs on which to transmit), and / or (6) at least one of one or more LBT configurations. The LBT configuration can be received by the WTRU 102 from a broadcast transmission, be semi-static in configuration, be determined based on an indication (e.g., a semi-static or dynamic indication), be determined from the timing between trigger signals, and / or be determined from the time gap between a trigger signal and an applicable uplink transmission. The LBT configuration or LBT parameters can include at least (1) a channel access priority class, (2) a category or type of LBT, (3) a contention window size, and / or (4) parameters used to determine that the UE can acquire a channel or transmit an uplink signal thereon.

[0112] On a PRACH resource, in order to perform PRACH preamble transmission 220, the WTRU 102 can perform an LBT operation before configuring the resource. The WTRU 102 can use an LBT configuration that can be associated with the transmission of the PRACH preamble 220. For example, the WTRU 102 can have a specific LBT configuration that is applicable (e.g., only applicable) to the transmission of the PRACH preamble 220.

[0113] In another exemplary operation, the WTRU 102 that desires and / or needs to transmit the PRACH preamble 220 can receive a PRACH preamble transmission trigger 210 (e.g., associated with one or more PRACH resources) before transmitting the PRACH preamble 220. The WTRU can expect to receive a signal indicating that the next PRACH resource is available. The receipt of the indication may affect the type of LBT (and / or LBT parameters) used for the PRACH resource. For example, (1) for a PRACH resource for which the WTRU 102 did not receive a PRACH trigger signal 210 (e.g., preamble transmission trigger) therefor, the WTRU 102 can use a full LBT procedure before transmitting the PRACH preamble 220, and (2) for a PRACH resource for which the WTRU 102 received a PRACH preamble transmission trigger 210 (e.g., PRACH trigger signal) 210 therefor, the WTRU 102 can use a higher priority LBT (e.g., an LBT configuration whose parameters can be relaxed to increase the likelihood of channel acquisition), or not use the LBT procedure at all.

[0114] In another exemplary embodiment, a WTRU 102 (e.g., triggered to perform RA) may perform a LBT operation and / or another channel access procedure such that there can be a period of time between the end of the LBT operation and the start of PRACH preamble transmission 220. During this gap (e.g., this gap period), the WTRU 102 may listen to determine whether the PRACH trigger signal 210 has been transmitted. When the PRACH trigger signal 210 is received and / or after reception, and when the channel was previously determined to be unoccupied (e.g., the LBT operation was successful), the WTRU 102 may transmit a PRACH (e.g., PRACH preamble transmission) 220 on an applicable PRACH resource. The WTRU 102 may be configured to use a resource (e.g., LBT configuration information including timing) on which the WTRU 102 can perform LBT (e.g., the LBT operation) for a next PRACH (or other UL) transmission. For example, the WTRU 102 may be configured to use a time offset between the end of the LBT operation and an associated UL transmission resource. The timing offset may enable, for example, the WTRU 102 to listen for the PRACH trigger signal 210 to verify a UL transmission (e.g., to verify use of a PRACH resource and / or to verify a UL grant).

[0115] The WTRU 102 can determine the RA procedure type, (e.g., an RA procedure using two operations or four operations), and / or the parameters of the RA procedure (e.g., in particular, the RAR and / or contention resolution timer, and / or the backoff value, as described herein) based on the timing of the LBT operation (e.g., when, whether, or if the LBT operation is to be performed), the success or failure of the RA procedure, and the reception or non - reception of the trigger signal 210. For example, if the WTRU 102 performs an LBT operation and / or determines that the channel is idle before receiving the trigger signal 210 and then receives the trigger signal 210 from the gNB 180, the WTRU 102 can use a first RA procedure type and a first set of RA procedure parameters. In another example, if the WTRU 102 receives the trigger signal 210 without first performing an LBT operation (or after failing the LBT operation for RA before receiving the trigger signal 210), the WTRU 102 can then perform an LBT operation (the parameters of which can be determined based on the reception of the trigger signal 210) and, upon and / or after the success of the LBT operation, use a second set of RA procedure parameters and a second RA procedure type. In a further example, a WTRU 102 (e.g., that receives the trigger signal 210 and fails the LBT operation before and / or after the reception of the trigger signal 210) can perform RA using a third RA procedure type and a third set of RA procedure parameters. In another example, a WTRU 102 (e.g., that performs LBT and determines that the channel is idle but has not received the trigger signal 210) can perform RA using a fourth set of RA parameters and a fourth RA procedure. As used herein, the term UL LBT failure implies that after the CCA part of the LBT procedure, the UE was unable to acquire a channel for an uplink transmission attempt, which can be determined based, among other determination methods, on the reception of a "LBT failure notification" or "LBT failure indication" from the physical layer.When the term uplink LBT success is used, the opposite is true.

[0116] (1) Failed in the LBT operation and / or (2) Despite not receiving the trigger signal 210, the ability to perform RA can depend on the RA trigger. For example, a subset of the RA trigger can enable the WTRU to perform a PRACH transmission 220 (1) having failed in the LBT operation (e.g., before, upon, or after the reception of the trigger signal 210) and / or (2) despite having failed to receive the trigger signal 210. In another procedure / process, (1) having failed in the LBT operation and / or (2) despite not receiving the trigger signal 210, the ability to perform RA can depend on the service type for which the RA is being performed.

[0117] - Representative trigger signal - The trigger signal (e.g., the PRACH preamble transmission trigger 210) can be an implicit indication or an explicit indication. An example of implicit triggering is that when the WTRU 102 receives a transmission from the network (e.g., the gNB 180), the WTRU 102 can expect that the next PRACH resource is available. Such a transmission can include, among other things, (1) one or more discovery reference signals (DRS), (2) one or more synchronization signal blocks (SSB), (3) one or more reference signals (RS), (4) one or more control channels (e.g., PDCCH), and / or (5) one or more master information blocks (MIB) / system information blocks (SIB). For example, the WTRU 102 that receives a DL transmission from the network (e.g., a network entity such as the gNB 180) can determine and / or assume that the PRACH resource (e.g., any PRACH resource) within the COT associated with the DL transmission is available. In another example, the WTRU 102 can start a timer after or upon receiving a DL transmission, and the PRACH resource (e.g., any PRACH resource) that occurs (e.g., is used) before the expiration of the timer can be considered available by the WTRU 102 or available for transmission using a certain LBT configuration. In one representative embodiment, the WTRU 102 can use the reception of an SSB as a trigger and / or consider it a trigger for a PRACH resource associated with one or more SSBs.

[0118] The WTRU 102 can determine / anticipate that the transmission of a signal explicitly indicates that one or more next PRACH resources are valid. For example, the WTRU 102 can attempt to monitor a broadcast channel to receive an indication of a valid PRACH resource. In another example, the WTRU 102 can attempt to monitor a PDCCH (e.g., a group common PDCCH or a PDCCH destined for the WTRU) to receive a trigger signal 210 (e.g., a PRACH resource trigger signal). The WTRU 102 can monitor a certain search space and / or core set to receive a trigger signal 210 (e.g., a PRACH resource trigger signal).

[0119] Such an indication can indicate a preconfigured or scheduled PRACH resource. For example, the indication can provide a PRACH resource configuration (e.g., a dynamic PRACH resource indication).

[0120] When the WTRU 102 determines and / or anticipates using one of a preconfigured set of PRACH resources, the WTRU 102 can monitor a specific instance and / or channel for which a trigger signal 210 can be transmitted for a PRACH resource (e.g., each PRACH resource). For example, a relationship (e.g., one-to-one, many-to-one, or one-to-many) can exist between one or more triggering signals 210 and one or more PRACH resources. The WTRU 102 that determines, plans, desires, and / or wishes to use the next PRACH resource can monitor one or more specific instances for which a triggering signal 210 can be received. For such an operation, an implicit (predetermined, pre-known, and / or communicated) relationship can exist between one or more trigger signal occasions and one or more PRACH resources.

[0121] In another operation, the WTRU 102 can be configured to use a trigger signal pattern (e.g., PRACH resource trigger signal monitoring patterns). For example, when required and / or appropriate, the WTRU 102 can monitor a PRACH resource trigger signal occasion (e.g., all PRACH resource trigger signal occasions). The WTRU can expect (e.g., be configured to provide) that the trigger signal provides a PRACH resource configuration.

[0122] - Representative trigger signal content - The trigger signal 210 (e.g., a PRACH resource trigger signal) can provide a PRACH resource configuration, such as defined herein. The PRACH resource trigger signal 210 can indicate the validity of a set of preconfigured PRACH resources. For example, the PRACH resource trigger signal 210 can provide a subset of the configuration (e.g., resource allocation, preamble, and / or interleaving) for one or more next PRACH resources.

[0123] The trigger signal 210 (e.g., a PRACH resource trigger signal) can indicate the validity of PRACH resources on one or more subbands. For example, for the WTRU 102 in the connected mode, the PRACH trigger signal 210 (e.g., a PRACH resource trigger) can provide an instruction to perform RA on a given PRACH configuration. For example, the PRACH trigger signal can cause and / or instruct one or more WTRU 102s to perform an RA operation on a given subband, one or more preambles, and / or one or more PRACH resources. Similarly, the WTRU 102 can be instructed on the PDCCH to perform an RA operation, including RA on different subbands.

[0124] The PRACH resource trigger signal (e.g., PRACH resource trigger) can indicate one or more purposes (e.g., a set of purposes) for which the PRACH resource can be used, and the WTRU 102 can transmit (e.g., transmit only) a PRACH preamble if the preamble is for one of the purposes indicated by the PRACH resource trigger signal 210. The PRACH preamble purpose for a PRACH resource can likely include, along with the service type, any of (1) initial access, (2) beam failure recovery (BFR), (3) mobility (e.g., handover), (4) lost UL synchronization, (5) RRC connection re - establishment, (6) scheduling request (SR) transmission, and / or (7) timing pre - acquisition. The PRACH resource trigger can indicate either (1) the priority of the RA for which the PRACH resource is valid, and / or (2) the set of WTRUs 102 for which the PRACH resource is valid. For example, a group radio network temporary identifier (RNTI) can be included within the PRACH resource trigger.

[0125] For a NR-U cell that is beamformed, the WTRU 102 may determine that a subset of the SSBs within the SS burst was not transmitted or was delayed due to an LBT failure (e.g., an LBT operation failure), and / or similarly, for CSI-RS, the WTRU 102 may determine that one or more CSI-RSs (e.g., all or a subset of the CSI-RSs) were not transmitted or were delayed due to an LBT failure. The trigger signal after the SS burst can indicate, among other things, (1) a change in the configured association rules between the SSB (and / or CSI-RS) and the PRACH occasion / preamble, (2) the availability and / or applicability status of a subset of the SSBs (and / or CSI-RSs) for selection when determining which SSB / CSI-RS to select (or which corresponding PRACH occasion / preamble to select), (3) one or more additional PRACH occasions, such as with an association to a particular SSB / CSI-RS, and / or (4) a time offset for one or more applicable dynamic PRACH occasions, and / or can imply the same.

[0126] In one exemplary embodiment, the indication can be explicit (e.g., based on the content and / or characteristics of the trigger signal 210). In other exemplary embodiments, the indication can be implicitly determined by the WTRU 102 from (1) the trigger signal 210, (2) the sequence of SSB and / or CSI-RS transmissions, and / or (3) other gNB transmissions.

[0127] The WTRU 102 may determine that a certain SSB or certain SSBs were not transmitted or were transmitted with a timing offset with respect to a configured SSB transmission occasion, due to, for example, an LBT failure (e.g., an LBT operation failure) in a network entity (e.g., a gNB). The WTRU 102 may change (e.g., subsequently change) the association rules that map PRACH occasions and / or preambles to SSBs.

[0128] For example, the WTRU 102 may determine that a PRACH occasion and / or preamble associated with a missing SSB (and / or CSI-RS) no longer indicates the missing SSB. The WTRU 102 may further reuse the PRACH occasion / preamble associated with one or more SSBs that were not transmitted prior to the timing of these PRACH occasions, for different purposes and / or for different indications. For example, the WTRU 102 may use these PRACH resources for the indication of other transmitted SSBs.

[0129] Regarding preamble retransmission, the WTRU 102 can determine to wait for the next PRACH occasion (e.g., the WTRU 102 should wait) when the SSB selected for the initial transmission cannot be found due to an LBT failure on that SSB before the preamble retransmission. For example, when a previously selected SSB was not transmitted due to LBT (e.g., due to an LBT failure occurring), even if other SSBs are available and / or the LBT operation for other SSBs was successful, it may be useful for the WTRU 102 not to change the SSB for preamble retransmission, for example, to maintain the progress of the power ramping status for the previously selected beam. In such a case, the WTRU 102 can refrain from incrementing the power ramping counter and / or the preamble transmission counter when the associated PRACH occasion is skipped. For example, up to a limited number of retransmissions or while a certain timer (which can be configured by a higher layer and / or via network signaling) is running, the WTRU 102 can skip or further skip the RACH occasion associated with the SSB selected using a previous PRACH transmission.

[0130] In one representative embodiment, with respect to preamble retransmission in a beamformed NR-U cell, the WTRU 102 may determine that it can select a PRACH occasion / preamble associated with an SSB selected for an initial and / or previous transmission, even if the current SSB transmission is not found due to an LBT failure. The WTRU 102 may determine from an indication by the network that a particular SSB was not transmitted (e.g., due to an LBT failure), or the WTRU 102 may autonomously determine that the SSB was not transmitted (e.g., due to an LBT failure). The WTRU 102 may follow, or further follow, such behavior for example, up to a limited number of retransmissions, or while a certain timer is running, which can be configured by a higher layer and / or via network signaling.

[0131] - Representative WTRU Behavior for Receiving a Trigger Signal - After, or upon, determining that the WTRU 102 should transmit, or has been triggered to transmit, the PRACH preamble 210, the WTRU 102 may begin monitoring for a PRACH resource trigger signal. The WTRU 102 may be configured to use a monitoring pattern to detect the PRACH resource trigger signal. The configuration can be provided on a broadcast channel and / or can be RRC configured. Upon or after receiving the PRACH resource trigger signal, the WTRU 102 may attempt to transmit a PRACH preamble on the associated PRACH resource. In a first example, receiving the indication may enable the WTRU 102 to use multiple PRACH resources, for example, for PRACH retransmission. In another example, the WTRU 102 may receive different PRACH resource trigger signals for the PRACH resources used for preamble retransmission (e.g., for any PRACH resource).

[0132] The trigger signal can be received from a PDCCH that is monitored in a common and / or WTRU-specific search space. The RNTI used to mask the cyclic redundancy check (CRC) of the PDCCH can be pre-determined, for example, as part of the system information, or configured by a higher layer. In addition to or instead of configuring the RNTI as part of the system information, the RNTI can be configured, for example, by dedicated signaling, or can correspond to a Cell-RNTI (C-RNTI). Enabling multiple RNTIs (e.g., one provided by the system information and a second corresponding to the C-RNTI) can enable the network to flexibly configure one or more resources for either contention-based RA and / or contention-free RA.

[0133] -Typical Triggering by RAR- In one exemplary embodiment, when it is necessary and / or desired to perform an RA procedure, the WTRU 102 can begin monitoring a pre-configured search space and attempt to receive a gNB-triggered RAR. The RAR can be transmitted by the gNB, for example, without first receiving a preamble transmission. For example, the WTRU 102 can monitor the search space and receive control signaling indicating that a spontaneous RAR has been transmitted. The RAR can provide one or more UL grants for performing msg3 transmission to one or more WTRU 102, along with applicable transmission characteristics including one or more applicable LBT configurations.

[0134] The WTRU 102 can receive a RAR that includes an identifier identifying one or more WTRU 102 for which the RAR and / or UL grant is valid. The RAR can include an RA purpose as described herein for which the indicated UL grant can be used.

[0135] The RAR can include a set of grants. For example, to determine to perform RA, the WTRU 102 that desires and / or requires can select a grant from a set of UL grants. The selection of the grant can be random (e.g., completely random). In another example, the selection of the grant depends, inter alia, on (1) the expected timing advance (TA) range (e.g., the WTRU 102 can select a grant based on the expected range of TA values), (2) the RA-RNTI, (3) the RA preamble ID, (4) the service type, (5) the UL and / or DL beam (e.g., based on measurements on the DL RS, e.g., the WTRU 102 can have a preferred UL beam and / or a preferred DL beam), (6) the amount of data to be transmitted, (7) the RA purpose, and / or (8) a previously failed msg3 transmission (e.g., if a previous UL grant transmission fails, the WTRU 102 can select a more robust UL grant for the next attempt in RA).

[0136] - Representative operations for reducing the number of LBTs per RA procedure - - Single LBT - RA procedure - To reduce the number of LBTs used or required for each message transmission in a single RA procedure, channel access can be shared between the WTRU 102 and a network entity (e.g., gNB 180) using COT sharing with one or more switching points. COT sharing can be implemented (e.g., considered) when UL and DL RA messages are transmitted on the same channel in a time-division duplex frame structure.

[0137] For example, when obtaining a channel for transmitting a message (e.g., message 2 (msg2)), gNB 180 can continue to occupy the channel until gNB 180 transmits message 4 (msg4). For each provided grant for msg3 transmission, gNB 180 can communicate or imply (e.g., based on the parameters indicated in the message or the message itself) a COT switching point together with the LBT configuration, and can stop occupying the channel during the grant PUSCH duration. WTRU 102 may or may not perform a short LBT before transmitting msg3, which can result in reducing, for example, the number of LBTs per RA procedure and / or the number of full LBTs, and each transceiver can obtain the channel a limited number of times (e.g., only once). Similarly, after transmitting msg3, WTRU 102 can hold the channel until WTRU 102 receives another grant for message 5 (msg5). In one representative embodiment, the short LBT operation can listen for a shorter period or can determine that the channel is available based on a less stringent criterion than the long LBT operation.

[0138] - Representative adjustment of the RAR timer and / or the contention resolution timer - The WTRU 102 can monitor the PDCCH during a time period before the expiration of one or more timers (e.g., ra-ResponseWindow) and / or (e.g., ra-ContentionResolutionTimer). For example, if the timer ra-ResponseWindow expires without the WTRU 102 receiving msg2, or if the ra-ContentionResolutionTimer expires without the WTRU 102 receiving msg4, the WTRU 102 can determine (e.g., assume) that a preamble retransmission is appropriate (e.g., is required). For NR-U, the gNB 180 may fail to acquire the channel after LBT, resulting in the PDCCH for msg2 and / or msg4 not being transmitted. In such cases, the WTRU 102 can benefit from extending the waiting time for msg2 and / or msg4 in order to complete the RA procedure before attempting another preamble retransmission.

[0139] The WTRU 102 may be able to determine that the gNB 180 has not acquired a channel for the transmission of the PDCCH for msg2 and / or msg4. The WTRU 102 may (1) be able to pause the timer ra-ResponseWindow and / or the ra-ContentionResolutionTimer for a period of time that the WTRU 102 determines that the channel is busy and / or the gNB 180 has not acquired the channel, (2) be able to reset the timer ra-ResponseWindow and / or the ra-ContentionResolutionTimer (e.g., once the WTRU 102 determines that the channel is busy and / or the gNB 180 has not acquired the channel), and / or (3) be able to add a time value to either the timer ra-ResponseWindow and / or the ra-ContentionResolutionTimer (e.g., once the WTRU 102 determines that the channel is busy and / or the gNB 180 has not acquired the channel), including any of several actions (e.g., helpful and / or necessary actions) to extend the PDCCH monitoring period. One or more added time values may depend on a configured value and / or be based on the duration that the channel was determined to be busy during. One or more added values may be randomly determined by the WTRU 102 from a set of possible values.

[0140] - Diversity of Representative Messages 1 / 2 / 3 / 4 - In one representative embodiment, it is possible to perform the transmission of a plurality of messages (e.g., msg1, msg2, msg3, and / or msg4) on different resources and / or, for example, within different sub-bands, which may be beneficial (e.g., each message can be associated with its own LBT procedure). For example, in a high channel occupancy state where two or more RATs can share a channel, acquiring a wideband channel using wideband LBT to transmit a single message may not be efficient, for example, based on (e.g., when considering) the OCB requirements. Diversity of the PRACH preamble, RAR, msg3, and / or msg4 can be achieved by attempting to transmit these messages with a set of different resources and / or LBT sub-bands, where each resource can use and / or require independent LBT. This diversity can provide robustness against failure to acquire a channel within one or more LBT sub-bands. The WTRU can attempt such transmit / receive diversity depending on the preamble retransmission count and / or RRC configuration, and / or any of the following, namely, inter alia, (1) the preamble attempt count and / or the preamble transmission count, (2) the indexes of the UL BWP and the DL BWP, and / or (e.g., if configured and / or if valid) the linkage between the UL BWP and the DL BWP, (3) whether a timer (e.g., the BWP inactivity timer) is running or has expired, (4) the observed channel occupancy / load state on the monitored sub-band / BWP, (5) a certain static or semi-static configuration (e.g., received via RRC and / or SI signaling) for the WTRU or applicable PRACH resources, and / or (6) the ability of the WTRU102 to support a plurality of active BWPs.

[0141] For example, the WTRU 102 can be configured to attempt to transmit multiple msg1s using different sub - bands, PRACH resources, preambles, and / or interlaces. For msg2 and / or msg4, the WTRU 102 can be configured to attempt to receive at least one RAR / Contention Resolution on different sub - bands, core sets, and / or BWPs.

[0142] For msg3, the WTRU 102 can receive multiple grants to transmit msg3. For example, the WTRU can receive a Msg2 PDU that includes or contains multiple MAC RARs for the same preamble ID (e.g., each containing or including a different uplink grant), or an extended MAC RAR that can include or contain multiple UL grants. The WTRU 102 can transmit one or more messages (e.g., msg3) according to the LBT result for a grant (e.g., each grant), e.g., for a single UL grant for which LBT was successful. For example, the WTRU 102 can receive multiple grants in msg2 for msg3 transmission on different subbands. The WTRU 102 can apply a separate LBT procedure for each selected grant for msg3. In another example, the WTRU 102 can receive multiple grants in mgs2 for msg3 transmission on the same subband. The WTRU 102 can apply a single LBT procedure and transmit multiple msg3s. In a further example, the WTRU 102 can receive one or more msg2s, each of which includes (e.g., accompanies) one or more UL grants for msg3 (e.g., each msg2 can indicate one or more different msg3 grants). The WTRU 102 can transmit a single msg3 on any one or subset of the available resources (e.g., channel resources) associated with the provided msg3 grant. For example, the availability of channel resources can be determined from the result of the LBT procedure.

[0143] -Representative LBT Procedure for PRACH Transmission- PRACH preamble selection can enable multiplexing of PRACH transmissions on the same PRACH resource by a set of WTRUs 102. When transmitting a PRACH, it is conceivable that the WTRU 102 may not perform time alignment. In such a case, an early PRACH preamble transmission by a first WTRU 102a may result in a failed LBT by a second WTRU 102b. The LBT procedure for PRACH transmission can be modified to reduce and / or substantially eliminate such interference. In a first exemplary procedure, the interference threshold used in the clear channel determination portion of LBT can be set to a different value for PRACH transmission than for other UL and / or DL transmissions.

[0144] In an exemplary procedure, the interference threshold used for clear channel determination can vary over the course of the LBT procedure. For example, the WTRU 102 can determine, and / or may need to determine, N CCA slots in which the channel is idle. For the set of CCA slots that are closest in time to the transmission of the PRACH, the WTRU 102 can use a different (e.g., higher) interference measurement threshold than for other CCA slots in the LBT procedure, e.g., it can enable the WTRU 102 to avoid determining that a CCA slot is busy when the slot is being used by one or more other WTRUs 102 with, e.g., different timing alignments.

[0145] In an exemplary procedure, the WTRU 102 can use a timing offset between the end of the LBT process / procedure and the timing of UL transmission. An LBT process / procedure that was not determined to be successful prior to the time determined by the offset and the timing of UL transmission can be considered to have failed, and it can be determined that transmission (e.g., for that UL resource) cannot occur.

[0146] In one representative procedure, the WTRU 102 can adjust the CCA window / LBT process / procedure length, the start time of the CCA, and / or the start timing of the uplink transmission using a previously obtained TA value. The WTRU 102 can determine whether the TA value is valid based on the mobility status. The WTRU 102 can estimate the TA value (e.g., based on a certain cell configuration and / or downlink measurements) to adjust the start and / or length of the CCA, or the start of the actual uplink transmission.

[0147] In one representative procedure, the WTRU 102 can use a shortened LBT process / procedure for one or more transmissions that can be multiplexed with other WTRU 102s. The shortened LBT process / procedure can use, or request that the WTRU 102 determine, a smaller number N of CCA available CCA slots, and for the remainder of the LBT, the WTRU 102 can ignore the measurements on the CCA slots and can include their durations over different times. The use of alternative LBT procedures can enable WTRU multiplexing (e.g., using a set of thresholds, using a shortened LBT process / procedure where each threshold is associated with a set of applicable CCA slots, using an offset between the end of the LBT process and the UL transmission, or being an access class category) The LBT type can be determined as a function of the UL transmission type and / or resources. This can enable multiplexing of different UL transmissions. For example, the WTRU 102 can be permitted UL resources within the same slot and / or set of symbols as PRACH resources. In such cases for (e.g., permitted and / or configured) UL transmissions, the WTRU 102 can use an LBT configuration that includes or indicates a variable CCA threshold, and / or a timing offset between the end of the LBT and the start of the transmission.

[0148] WTRU102 can determine that it can transmit a UL transmission in the same slot and / or symbol as another UL transmission from another WTRU102. Depending on whether the WTRU102 expects other WTRUs transmitting simultaneously to be time-aligned, the WTRU can use different LBT processes / procedures (and / or LBT parameters). For example, if the WTRU102 is transmitting on a resource that overlaps or can actually overlap with a PRACH resource, the WTRU102 can use a first set of LBT parameters. If the WTRU102 is transmitting on a resource that cannot overlap with a PRACH resource, the WTRU102 can use a second set of LBT parameters.

[0149] The WTRU102 can determine the type of LBT procedure, along with the associated parameters (e.g., thresholds and associated sets of CCA slots), based on, for example, the access class priority of the transmission.

[0150] The WTRU102 can indicate the presence or absence of a UL transmission in an adjacent slot that occurs before (e.g., immediately before) the UL resource of the WTRU102 (e.g., a resource for PRACH, PUSCH, and / or PUCCH, etc.). For example, it can enable the WTRU102 to use different LBT types and / or different parameters associated with the WTRU102. For example, for the case where it is indicated that another WTRU102 (e.g., another WTRU102 served by the same gNB180) is transmitting on the resource immediately before the UL resource of the WTRU102, the WTRU102 can use or require a shorter clear channel assessment time and use the LBT procedure. It can indicate the timing at which such an LBT procedure can be or should be performed. For example, the timing of the LBT procedure can be a plurality of slots before the actual transmission.

[0151] -Representative Interleaved Transmission- OFDM-based interleaving for UL transmission can be used, for example, in an unlicensed spectrum to improve UL capacity. The PUSCH channel and the PRACH channel (e.g., from the same WTRU 102 or different WTRU 102s) can be interleaved independently and / or dependently. The WTRU 102 can interleave the PUSCH and / or the PRACH in a number of ways, inter alia, based on, for example, (1) network configuration, (2) received network signaling, and / or (3) pre-set rules. The network signaling can be dynamic (e.g., using L1 / L2 signaling), semi-static (e.g., using L2 / L3 signaling), and / or pre-set. For example, the WTRU 102 can, inter alia, use any of the following procedures, in which (1) the PUSCH is interleaved and the PRACH is not interleaved (e.g., the PRACH signal can be transmitted continuously in the frequency domain (e.g., in a PRB included in or contained in a resource located in a gap between two parts (e.g., PRBs) of the other PUSCH interleaving or during the other PUSCH interleaving). In other representative embodiments, the PRACH can be transmitted in contiguous PRBs that may be interrupted by one or more PRBs used for PUSCH interleaving), (2) The PUSCH and the PRACH are transmitted using different interleaves (e.g., the PRACH and PUSCH channels, whether from the same WTRU 102 or different WTRU 102s, can be interleaved together. The WTRU 102 can determine the interleaving pattern for each channel. The WTRU 102 can determine the PRACH interleaving from the PUSCH interleaving pattern. The WTRU 102 can indicate one or more possible associations between the PRACH interleaving and the PUSCH interleaving. For example, the PRACH interleaving and / or preamble can be associated with a specific PUSCH interleaving. In another example, the WTRU 102 can determine the linkage between the PRACH interleaving and the PUSCH interleaving from a function (e.g., using the WTRU ID as an input)), and / or (3) The PUSCH and the PRACH are transmitted using, among other things, a single interleaving (e.g., this is for when PRACH transmission and PUSCH transmission are desired for a single WTRU 102. For example, the PRACH sequence can be combined with the PUSCH data before mapping the information to the sub-carriers / PRBs of the interleaving. The WTRU 102 can apply a certain remapping of the combined PRACH / PUSCH sequence before mapping it to the physical resources).

[0152] Regarding the two-step RACH operation, a single WTRU 102 can transmit both the PUSCH and the PRACH for the combined first RACH message (eMsg1, or combined Msg1) and / or may need to transmit. The WTRU 102 can transmit on both channels simultaneously or non-simultaneously based on the association between the PRACH resource / preamble used and the corresponding PUSCH used to carry the data payload. The WTRU 102 can determine whether to transmit on both channels simultaneously or non-simultaneously considering any of the following, namely, (1) the power headroom of the WTRU 102 and / or uplink transmit power, (2) the channel occupancy status and / or the remaining time in the COT, (3) the preamble retransmission count, (4) reception on network signaling including, for example, the RACH trigger signal, and / or (5) the purpose or type of the RA.

[0153] For example, the WTRU 102 can select a resource for the data to be generated in the first available UL resource for data transmission following the transmission of the preamble, and such a resource can be provided to the WTRU 102 through network signaling. The PUSCH interleaving and the PRBs selected by the WTRU 102 to transmit the data payload portion of eMsg1 can be selected by any of the procedures described below.

[0154] When eMsg1 is transmitted in an NR-U cell, the WTRU 102 can set, determine, and / or assume the association between the selected PRACH resource and the PUSCH interleaving (in addition to other PUSCH resource characteristics). The WTRU 102 can use any of the following, namely, (1) A fixed or pre - defined procedure, which is pre - configured in the WTRU102 and assumed / set for all WTRU102s. For example, the WTRU102 can select an inter - leave using a fixed or pre - defined procedure based on its WTRU identity. (2) From information provided in system information, such as through broadcast on the SIB, or provided in an access table. (3) Based on an explicit indication, such as explicitly indicated in DCI or in a downlink control message (e.g., especially, MAC CE message and / or RRC message). (4) Based on a selected preamble (e.g., the selected preamble can be associated with a specific inter - leave used. The association can be fixed or configured by the network). (5) Based on a selected PRACH resource (e.g., the PRACH resource can be associated with a specific inter - leave used. The association can be fixed or configured by the network). (6) Based on random selection (e.g., the WTRU102 can select from a set of possible PUSCH inter - leaves. The number of possible inter - leaves available to the WTRU102 can be further determined by any of the representative procedures / processes / methods described hereinabove). (In addition to other PUSCH resource characteristics), the PUSCH inter - leave associated with the selected PRACH can be determined.

[0155] - Representative RA procedures in unlicensed spectrum - - Representative back - off procedures - Figure 3 is a diagram illustrating a representative back - off procedure (e.g., a random back - off applied by the WTRU102 after an LBT failure) used with the LBT operation.

[0156] Referring to Figure 3, the RA procedure 300 can include a first WTRU 102a that can desire to initiate the RA procedure and can initiate an LBT operation 330a. The first WTRU 102a can determine that the channel is busy (e.g., during the channel busy period 315) and can start a first backoff timer. The value of the first backoff timer can be set, for example, randomly or based on the RA priority. Thereafter, a second WTRU 102 can desire to initiate the RA procedure and can initiate an LBT operation 330b. The second WTRU 102b can determine that the channel is busy (e.g., during the channel busy period 315) and can start a second backoff timer. The second backoff timer can expire before the expiration of the first backoff timer, and the second WTRU 102b can start its second LBT operation 340b. Since the channel is now available, the second WTRU 102b can transmit its RA preamble 320b. Thereafter, the first backoff timer can expire (e.g., after the expiration of the first backoff timer), and the first WTRU 102a can start its second LBT operation 340a. Depending on the timing, the channel can be available (e.g., the second WTRU 102b may not have acquired the channel yet). If so, the first WTRU 102a can transmit its RA preamble 320a. For example, if the channel is not available because the second WTRU has acquired the channel (not shown), the first WTRU 102a can start another backoff timer.

[0157] In one representative embodiment, when the channel is busy for an extended duration, a number of WTRU102s may desire or should execute the RA procedure when the channel becomes available again, so there may be a higher likelihood of collisions on the RACH. When a preamble collision occurs and the gNB180 fails to acquire the channel due to LBT (e.g., due to an LBT failure), the gNB180 does not have an opportunity to convey a backoff value for the colliding WTRU102s. In a scenario where multiple WTRU102s are attempting the RA procedure in an NR-U cell where the DL channel is occupied, the WTRU102s may continue to simultaneously retransmit the preamble on the UL channel without a backoff. Representative backoff procedures for reducing such collisions and retransmissions are described herein.

[0158] The WTRU102 can perform an LBT operation before transmitting the first preamble and can determine that the channel is not available.

[0159] Following the transmission of the preamble, the WTRU102 can determine that the RAR was not transmitted by the gNB180 (e.g., the channel is not available) due to an LBT failure. The determination can be based on, for example, among other things, (1) the WTRU102 detecting another WTRU that has acquired the channel (e.g., based on sensing a transmission having a certain characteristic that can indicate (e.g., implicitly indicate) one or more transmitters other than the gNB180 that has acquired the channel), (2) the WTRU102 detecting noise above a threshold on or for the associated resource, and / or (3) the WTRU102 not detecting a transmission having a certain characteristic (e.g., that can indicate (e.g., implicitly indicate) that the gNB180 has acquired and transmitted on the channel), such as on the PDCCH. and can be based on any of the foregoing.

[0160] In the above, the detection can be performed while the RAR timer is operating and / or when the RAR timer has expired.

[0161] In one exemplary embodiment, the WTRU 102 can then start a backoff timer. The backoff timer can start when the WTRU 102 detects that the channel is available (e.g., while detecting) and can be interrupted when the WTRU 102 detects that the channel is not available (e.g., while detecting). In one exemplary embodiment, the backoff timer can start immediately.

[0162] The WTRU 102 can receive a trigger signal as described herein. Upon receiving the trigger signal, the WTRU 102 can stop any ongoing backoff timer and / or start a new backoff timer.

[0163] The value of the backoff timer can be randomly selected between a minimum value and a maximum value. The minimum value and / or the maximum value can be, for example, predetermined, statically configured, semi-statically configured, and / or communicated. The minimum value and / or the maximum value can depend, inter alia, on (1) the subband on which the preamble was transmitted, (2) the number of preamble transmission attempts, (3) the preamble transmission counter value, (4) the channel load condition, (5) the duration of the period during which the channel was not available since the last preamble transmission, (6) whether the WTRU 102 has received a trigger signal (e.g., the minimum value and the maximum value can further depend on the characteristics of the trigger signal or can be explicitly indicated as part of the information carried by the trigger signal), (7) the priority of the logical channel (LCH) that triggered the RA (e.g., in the connected mode), and / or (8) whether the RA is considered a prioritized RA that includes an RA priority.

[0164] If the channel is busy and / or for example, if the WTRU 102 determines that the gNB 180 did not acquire the channel due to LBT, the WTRU 102 can adjust (e.g., further adjust, pause, and / or stop) the backoff timer. For example, if the WTRU 102 determines that the gNB 180 was unable to acquire or did not acquire the DL or UL channel due to LBT, for example, the WTRU 102 can pause the operating backoff timer, reset the timer, or adjust the value of the timer.

[0165] When the backoff timer expires, the WTRU 102 can perform preamble retransmission.

[0166] In another example, the WTRU 102 may determine that the RAR was not sent because the preamble was not decoded and / or not received by the gNB 180 (e.g., instead of being based on LBT), and the WTRU 102 can perform preamble retransmission without backoff.

[0167] In one exemplary embodiment, the gNB 180 can indicate in the RAR a backoff value applicable to one or more specific subbands that can be different from the subband on which the RAR with the backoff indication was received.

[0168] In one representative embodiment, where the backoff timer for a plurality of WTRUs 102 expires and the channel remains busy, the WTRU 102 can apply a further backoff (e.g., start another random backoff timer) when the channel becomes available, for example. This can be beneficial in preventing a large number of WTRUs 102 from attempting to access the channel simultaneously when the channel becomes available. The further backoff, or an indication to apply a further backoff, can be conveyed by the gNB 180 when the channel is available, configured semi-statically, and / or configured statically, among other things.

[0169] - Representative Msg1 Resource Selection Procedure - The WTRU 102 can maintain (e.g., further maintain) a preamble trial counter that can be incremented each time the MAC instructs the PHY to transmit a preamble, regardless of the result of the LBT, or each time a preamble transmission attempt fails the LBT. The WTRU can determine the number of attempts that have failed the LBT directly from the counter value or from the difference between the preamble transmission counter and the preamble trial counter.

[0170] The WTRU 102 may fail to acquire a channel for preamble transmission in Msg1, or may fail to receive a RAR after succeeding in LBT for preamble transmission. The WTRU 102 may attempt to transmit or retransmit Msg1 in different subbands, LBT bandwidths, interleaves, and / or preamble / PRACH occasions. Such channel switching may depend, inter alia, on any of the following: (1) the number of preamble retransmissions greater than a configured threshold, (2) the number of preamble attempts greater than a configured threshold, (3) the indexes of the UL BWP and the DL BWP, and / or (e.g., if configured and / or active) the linkage between the UL BWP and the DL BWP, (4) whether a timer (e.g., a BWP inactivity timer, or a timer for resetting the preamble attempt counter) is running or has expired, (5) the observed channel occupancy / loading state on the monitored subband / BWP, (6) a certain static or semi-static configuration, e.g., by RRC or SI, and / or (7) the ability of the WTRU 102 to support multiple active BWPs.

[0171] For example, the WTRU 102 can be configured to attempt to transmit or retransmit a preamble (or initiate another RA procedure) on a different subband or LBT channel compared to a previous attempt if, for example, a preamble attempt counter exceeds a configured number. The WTRU 102 can report the problem to a higher layer (e.g., notify the RRC and / or trigger an RLF). For example, the WTRU 102 can trigger an RLF after attempting a number of (LBT-failed) preamble transmission attempts on a number of LBT subbands (e.g., all subbands within an active BWP, or subbands on each BWP). In another example, the WTRU 102 can attempt to transmit or retransmit a preamble on a different subband if a BWP-inactivity timer is about to expire or has expired.

[0172] The WTRU 102 can attempt to transmit or retransmit a preamble on a UL BWP having the same index as the DL BWP that was active before RA was initiated, which can involve or include switching the active UL BWP, which can be beneficial in an NR-U situation (e.g., when the active DL BWP of the WTRU 102 has less load / channel occupancy than the DL BWP with the same index as the active UL BWP before RA was initiated). This can be contrasted with the behavior in an NR license where the WTRU 102 may switch its active DL BWP to a DL BWP having the same index as the active UL BWP when RA is initiated.

[0173] For preamble transmission attempts, when switching to different sub - bands and / or BWPs, the WTRU102 can stop the ongoing RA procedure and resume a new procedure on the new sub - band and / or BWP. In one example, the WTRU102 can continue the ongoing RA procedure after changing the sub - band and / or BWP if the PHY (e.g., PHY layer) has not transmitted any preambles since the start of the procedure. The WTRU102 can reset the preamble attempt counter when switching the BWP / sub - band and / or after switching if, for example, the RA procedure is not reset. The WTRU can also reset the preamble attempt counter when the associated reset timer configured by the RRC expires.

[0174] Since the result of LBT may not be known to the Media Access Control (MAC), the MAC may not recognize whether the PHY has transmitted a PRACH physical signal, and the MAC can increment the preamble_transmission_counter (e.g., if the PHY indicates that a preamble was transmitted after LBT was successful and no RAR and / or contention resolution was received).

[0175] After the PHY indicates to the MAC that a preamble has been transmitted and LBT was successful, the WTRU102 can start the ra - ResponseWindow. This can be beneficial, for example, to avoid unnecessary PDCCH monitoring when the preamble was not actually transmitted at the PHY (e.g., physical layer).

[0176] The MAC can consider and / or use the LBT result for preamble retransmission before changing the preamble_power_ramping_counter. For example, the MAC can increment the preamble_power_ramping_counter when any of at least the following occur, namely, (1) for a previous preamble transmission, RAR and / or contention resolution was not received, (2) the MAC selects a preamble for retransmission on the same UL / DL channel as used in the previous preamble transmission, and / or (3) the PHY indicates that the preamble was transmitted after LBT was successful.

[0177] For PRACH selection in NR-U access, the WTRU102 can calculate the RA-RNTI based on the selected PRACH resource. The WTRU102 can include information about the selected PRACH interleaving part of the RA-RNTI calculation. For example, (1) f_id can be defined / extended as a function of the selected interleaving, and / or (2) the formula can directly consider the selected interleaving ID.

[0178] -Typical RAR reception procedure- In one representative embodiment, the WTRU 102 can expect that the RAR is transmitted on any of a set consisting of a sub-band, an interlace, or a set of resources. The WTRU 102 can monitor a set of control resource sets (e.g., the RAR monitoring set). The set of control resource sets can span multiple sub-bands and can enable reception of the RAR on multiple sub-bands (e.g., to enable a greater likelihood of successful channel access for transmission of the RAR by the gNB 180). The control resource sets within the RAR monitoring set can have different periodicities and offsets (e.g., each having). The RAR monitoring set can be determined based on a broadcast channel (e.g., including the MIB and / or SIB). In one representative embodiment, the RAR monitoring set can be determined based on a selected PRACH preamble and / or PRACH resource.

[0179] The RAR (or RAR MAC CE) can include an indication regarding one or more sub-bands and / or one or more bandwidth parts (BWPs) on which the preamble was received. For example, the indicated sub-band can refer to any sub-band and / or BWP within the cell. The indication can be useful when the linkage between the UL BWP and the DL BWP is not intended / assumed (e.g., when the indices of the UL BWP and the DL BWP do not match). The RAR (or RAR MAC CE) can include an indication regarding the cell on which the preamble was received.

[0180] The WTRU 102 can monitor the RAR on multiple SSBs or CSI-RSs. For example, if a selected PRACH preamble and / or resource is associated with two or more SSBs (or two or more CSI-RSs), the WTRU 102 can monitor the RAR on the SSBs (e.g., all SSBs) associated with the selected PRACH preamble / resource.

[0181] -Typical RA prioritization procedure- In the case of NR-U access, the prioritized RA procedure can use a differentiated LBT window and / or configuration compared to non-differentiated RA. The WTRU 102 can apply different LBT windows and / or configurations, for example, according to the RA priority.

[0182] When applying a specific value to the LBT window and / or configuration, the WTRU 102 can determine and / or consider the number of preamble transmissions and / or retransmission attempts before the current attempt. When applying a specific value to the LBT window and / or configuration, the WTRU 102 can determine and / or consider the subband on which the WTRU 102 attempts to transmit the preamble. For example, the specific value for the LBT window and / or configuration can be based, inter alia, on (1) the number of preamble transmissions and / or attempts, and / or (2) the subband on which the WTRU 102 attempts to transmit the preamble.

[0183] -Typical scheduling request (SR) in unlicensed spectrum- -Typical LBT effect on PUCCH transmission- The WTRU 102 can be configured to use PUCCH resources (e.g., to transmit scheduling requests or other UCI on the PUCCH). The PUCCH resources can include any of (1) one or more time resources (e.g., a set of symbols), (2) one or more frequency resources (e.g., a set of PRBs), (3) one or more precoders (e.g., an analog / digital / hybrid precoder (e.g., for a transmission beam)), (4) one or more cover codes (e.g., to enable orthogonal or non-orthogonal multiplexing), (5) an interleaving pattern (e.g., a subset of subcarriers and / or PRBs on which to transmit) and / or (6) an LBT configuration. The LBT configuration can be received by the WTRU 102 in a broadcast, multicast, or unicast transmission. The LBT configuration can be included in the received transmission or indicated in the received transmission. For example, the LBT configuration can be an indication that can be set semi-statically (e.g., over a period of two or more TTIs, slots, or mini-slots) and / or dynamically (e.g., for each TTI, slot, or mini-slot period).

[0184] - Representative LBT configurations per - SR configuration - In order to perform an SR transmission on a PUCCH resource, for example, the WTRU 102 can perform LBT before such a transmission on the resource (e.g., a configured PUCCH resource). The WTRU 102 can use an LBT configuration associated with the transmission of the SR configuration. For example, the WTRU 102 can have a specific LBT configuration (e.g., inter alia, an LBT type, a duration, and / or a set of parameters) that is applicable to (e.g., only to) the transmission of the SR, or that is specific to, for example, a given SR configuration, an LCH, or a logical channel group (LCG). For example, the WTRU 102 can be configured (e.g., by the RRC) to use a mapping between the SR configuration and the LBT configuration (and / or the LBT access class priority). In another example, the WTRU 102 can apply an LBT configuration configured for the LCH that triggered the SR before the PUCCH transmission.

[0185] - Representative procedure for a triggered PUCCH opportunity - In one representative embodiment, the WTRU102 can perform transmission of SR (and / or other UCI) on one or more PUCCH resources when the WTRU102 receives a trigger signal (sometimes referred to as a "PUCCH transmission trigger"). The PUCCH transmission trigger and its content can be similar to the trigger signals described herein for the PRACH. For example, the PUCCH transmission trigger can consist of, or include, DCI received on the PDCCH, in the common space, and / or in the WTRU-specific search space. The PUCCH transmission trigger can indicate, among other things, (1) the type of UCI to be transmitted, such as SR and / or HARQ-ACK, (2) an index for one or more valid resources, and / or (3) any of the transmission times. For example, the WTRU102 can expect to receive a signal indicating that the next PUCCH resource is valid. The reception of the signal / indication can affect the type of LBT (and / or LBT parameters) used for one or more PUCCH resources. For example, for a PUCCH resource for which the WTRU102 does not receive a PUCCH transmission trigger therefor, the WTRU102 can use full LBT before transmitting SR or other UCI on the PUCCH. For one or more PUCCH resources for which the WTRU102 receives a PUCCH transmission trigger therefor, the WTRU102 can (1) use a higher-priority LBT (e.g., an LBT configuration with relaxed parameters to increase the likelihood of channel acquisition), or (2) not use LBT (e.g., not use LBT at all).

[0186] It is contemplated that the representative trigger signals (and their content) described herein can be equally applicable to (e.g., used for) PUCCH resources and / or PRACH resources.

[0187] In some representative embodiments, the WTRU 102 may be permitted (e.g., only permitted) to transmit an SR on a configured PUCCH resource when, or conditional on, receiving a PUCCH transmission trigger indicating that the PUCCH resource is valid.

[0188] In some representative embodiments, the WTRU 102 may be permitted to transmit an SR on any of a first PUCCH resource (e.g., a periodic resource) and / or on a second PUCCH resource indicated by a PUCCH transmission trigger. These representative embodiments can improve the latency of SR transmission in scenarios where large portions of the periodic PUCCH opportunities for SR are lost due to high channel occupancy. The first and second PUCCH resources can be selected from first and second sets of PUCCH resources configured by the RRC and / or the MAC. For example, the first set of PUCCH resources can correspond to a first PUCCH resource index (e.g., occurring periodically), and the second set of PUCCH resources can correspond to a second PUCCH resource index (e.g., having a timing indicated by a PUCCH transmission trigger).

[0189] -Representative WTRU behavior for receiving a trigger signal- When the WTRU102 triggers the SR, and / or after triggering, and / or when the WTRU102 determines that it should or needs to transmit UCI on the PUCCH, and / or after the determination, the WTRU102 can start monitoring the PUCCH resource trigger signal. The WTRU102 can be configured to use a monitoring pattern for detecting the PUCCH trigger signal. The configuration can be provided on the broadcast channel and / or can be configured by RRC. Upon receiving the trigger signal, the WTRU102 can attempt to transmit the SR on one or more associated PUCCH resources. For example, receiving such an indication (e.g., the trigger signal) can enable the WTRU102 to use multiple PUCCH resources and / or SR configurations. Typical SR Procedure in Unlicensed Spectrum -Typical SR Procedure- Since the result of the LBT may not be known to the MAC (e.g., MAC layer), the MAC may not recognize whether the PHY has transmitted the SR. Once the PHY (e.g., physical layer) indicates that the SR has been transmitted after the LBT has succeeded, and / or after the indication, the MAC can increment the SR_Counter for the applicable SR configuration. The WTRU102 can start the sr - ProhibitTimer and monitor the PDCCH once the PHY indicates to the MAC that the SR has been transmitted and the LBT has succeeded. This typical procedure can be beneficial, for example, to avoid unnecessary PDCCH monitoring when the SR is not actually transmitted at the PHY.

[0190] The WTRU 102 can maintain (e.g., further maintain) an SR trial counter, which can be incremented when (e.g., each time) the MAC commands the PHY to transmit an SR, regardless of the result of the LBT, or each time an SR transmission attempt fails the LBT. Once and / or after the SR trial counter reaches a certain number of SR trials (e.g., a threshold level), the WTRU 102 can perform, among other things, any of the following: (1) retransmit the SR and / or switch to a different interleaving, sub-band, BWP, cell, and / or use other PHY characteristics, (2) initiate a RA procedure on a given cell, (3) report the problem to a higher layer (e.g., notify the RRC and / or trigger an RLF), and / or (4) change the LBT configuration used.

[0191] - Representative procedures for PUCCH resource selection - The WTRU102 may fail to acquire a channel for SR transmission and / or may fail to receive a PDCCH after succeeding in LBT for SR transmission. The WTRU102 may attempt to transmit or retransmit SR or RA-SR on different sub-bands, different interleaves, and / or different cells. This channel switching may depend, inter alia, on any of the following: (1) the number of SR retransmissions greater than a configured threshold, (2) the number of SR attempts greater than a configured threshold, (3) the indexes of the UL BWP and DL BWP, and / or (e.g., if configured and / or if valid) the linkage between the UL BWP and the DL BWP, (4) whether a timer (e.g., a BWP inactivity timer or a timer for resetting the SR attempt counter) is running or has expired, (5) the observed channel occupancy / loading state on the monitored sub-band / BWP, (6) a certain static or semi-static configuration, e.g., by RRC or SI, and / or (7) the ability of the WTRU102 to support multiple active BWPs.

[0192] For a WTRU102 enabling multiple active BWPs, the WTRU102 may be able to transmit an SR (e.g., transmit yet another SR) on different active BWP pairs and continue to monitor the PDCCH on the DL BWP linked to the UL BWP on which the first SR was transmitted. For example, the WTRU102 may trigger additional SRs on different sub-bands / BWPs according to (e.g., based on) the SR transmission counter and / or the SR attempt counter of the first pending SR and / or according to (e.g., based on) the channel occupancy state.

[0193] The WTRU 102 can initiate (e.g., further initiate) a RA procedure on different BWPs and / or cells when, for example, a certain number of SR retransmissions and / or attempts have been reached and / or after reaching that number. For example, the WTRU 102 can determine and / or observe that the DL BWP on which the PDCCH is transmitted is loaded (e.g., heavily loaded and / or loaded above a threshold level), while the active UL BWP is not loaded (e.g., lightly loaded and / or loaded below another threshold level). The WTRU 102 can initiate a RA procedure to change the active DL BWP of the WTRU 102. For example, the WTRU 102 can initiate a RA procedure on the UL BWP linked to the DL BWP that is lightly loaded, which may be beneficial, for example, for a WTRU 102 that allows only a single active DL BWP at a time. When switching to different LBT sub-bands and / or BWPs, the WTRU 102 can stop an ongoing SR procedure and resume a new procedure. The WTRU 102 can reset the SR attempt counter when, for example, the BWP / sub-band is switched and / or after switching, if the SR procedure is not reset. The WTRU can further reset the SR attempt counter when the associated reset timer configured by the RRC expires.

[0194] - Representative procedure for SR retransmission - FIG. 4 shows, for example, a representative procedure for SR retransmission where a timer (e.g., sr - ProhibitTimer) can be extended when the channel is busy (e.g., the U - NR DL and / or U - NR UL channel is busy).

[0195] Referring to Figure 4, a representative procedure 400 for SR retransmission can include a WTRU 102 that can trigger a buffer status report (BSR) or a scheduling request (SR). In one representative embodiment, the BSR can trigger the SR. For NR-U, the WTRU 102 can perform a LBT operation at 410 to determine, for example, whether an unlicensed frequency band uplink channel is available for transmission. If the uplink channel is available for transmission, the WTRU 102 can generate an SR and can transmit the SR to a network entity (e.g., gNB 180) at 420. A timer (e.g., an SR prohibition timer) can be started after or during the transmission of the SR, and the timer can expire after an SR prohibition period 430. If the WTRU 102 does not receive a response (e.g., a grant) before the SR prohibition timer expires, the WTRU 102 can attempt to reacquire the channel using another LBT operation at 440 and can transmit a second SR at 450. For example, if the downlink (DL) channel is busy at 460 (e.g., if the network entity cannot transmit a response (e.g., a grant)), the WTRU 102 can extend the SR prohibition timer. During the extended SR prohibition period at 470, the WTRU 102 can receive a grant via the downlink (e.g., on the PDCCH) using a predetermined or communicated delay period K2 (e.g., a delay within the range of 1 to 8 subframes or TTIs). After the delay period K2, the WTRU can attempt to acquire the channel using another LBT operation at 480 and can transmit information (e.g., a BSR) using the uplink (e.g., PUSCH), for example, via a BSR MAC CE. Thereafter, the WTRU 102 can cancel the SR.

[0196] In one representative embodiment, if the network entity (e.g., gNB 180) determines that it has failed to transmit the PDCCH due to an LBT failure (e.g., when the grant is not received by the WTRU 102), the WTRU 102 can extend or reset a timer (e.g., sr-ProhibitTimer) before the expiration of the timer. For example, the WTRU 102 can determine that the PDCCH was not transmitted because the channel was busy over a duration of time, and the WTRU 102 can add time (e.g., add a value representing the duration of time) to a timer (e.g., sr-ProhibitTimer) up to a certain maximum duration / value that it can configure (e.g., pre-configure, semi-statically configure, and / or be signaled by the network entity).

[0197] In other representative embodiments, the WTRU 102 can extend or reset a timer (e.g., sr - ProhibitTimer) when receiving a PDCCH after transmitting an SR for an uplink grant and / or after failing a LBT (e.g., LBT operation) for a grant provided by the PDCCH. The WTRU can expect to receive another UL grant when restarting and / or after restarting the sr - ProhibitTimer and can further monitor the PDCCH. For example, the WTRU 102 can reset the sr - ProhibitTimer or add a value to the sr - ProhibitTimer when receiving an uplink grant after transmitting an SR. The added value can be configurable, pre - defined, and / or dependent on the uplink grant duration and / or grant transmission time. The use of the added value can be beneficial, for example, when the WTRU 102 transmits an SR and then receives an uplink grant but cannot transmit a PUSCH, for example, due to an LBT failure. In another example, the WTRU 102 can extend or reset the sr - ProhibitTimer when and / or after failing a LBT operation for PUSCH transmission with a grant received after transmitting an SR.

[0198] Figure 5 illustrates an exemplary procedure for extending the SR prohibition timer that is used with the LBT operation (e.g., when and / or after failing a LBT for PUSCH transmission with a grant received after transmitting an SR, the WTRU 102 can extend the sr - ProhibitTimer).

[0199] Referring to FIG. 5, a representative procedure 500 for SR prohibition timer extension can include a WTRU 102 that can trigger a BSR or a scheduling request (SR). In one representative embodiment, the BSR can trigger an SR. For NR-U, the WTRU can perform an LBT operation at 520 to determine, for example, whether an unlicensed frequency band uplink channel is available for transmission. If the uplink channel is available for transmission, the WTRU 102 can generate an SR and can transmit the SR to a network entity (e.g., gNB 180) at 530. A timer (e.g., an SR prohibition timer) can be started after or at the time of transmission of the SR, and the timer can expire after an SR prohibition period 540. If the WTRU 102 receives a response (e.g., a grant 550) before the SR prohibition timer expires, the WTRU 102 can wait for a delay period K2 (e.g., a pre-determined or communicated delay period, e.g., a delay within the range of 1 to 8 sub-frames or TTIs) and can attempt to re-acquire the channel using another LBT operation at 560. If another LBT operation 560 fails, the WTRU can extend the SR prohibition timer for an extended period. At 570, a network entity (e.g., gNB 180) can transmit another grant to the WTRU 102 via a PDCCH in the DL. After receiving the grant, the WTRU 102 can wait for a delay period K2 and can perform a further LBT operation 580. After the further LBT operation is successful (e.g., the channel becomes available), the WTRU 102 can transmit information (e.g., a BSR report) using the UL (e.g., PUSCH), for example, via a BSR MAC CE. Thereafter, the WTRU 102 can cancel the SR.

[0200] In one representative embodiment, the WTRU 102 can extend or reset the sr - ProhibitTimer for a given SR configuration when and / or after transmitting a different SR on a different sub - band, BWP, and / or SR configuration. The value added to the timer can depend on (e.g., be based on) any of: (1) the periodicity of the SR configuration of the additional SR, (2) the value configured for the SR prohibition timer for the additional SR, (3) the HARQ timeline and / or round - trip time (RTT) of the BWP / sub - band on which the additional SR is transmitted, (4) the PDCCH monitoring period associated with the transmission of the additional SR, and / or (5) the characteristics of the grant received on the PDCCH. For example, the WTRU 102 can extend the sr - ProhibitTimer of a first pending SR when and / or after transmitting a different SR on a different BWP and / or SR configuration. This behavior may depend on (e.g., further depend on) the ability of the WTRU 102 to support multiple active BWPs.

[0201] - Representative Procedures for SR Cancellation - If the WTRU 102 has already transmitted an SR (e.g., after LBT has succeeded), when attempting to transmit an SR on a different sub - band and / or BWP and / or after the attempt, the WTRU 102 can (1) cancel the previous SR and trigger an additional one, or (2) hold (e.g., maintain) the previous pending SR and trigger an additional one (e.g., an additional SR). The decision by the WTRU 102 can depend on (1) the capabilities of the WTRU 102 for having (e.g., supporting) multiple active BWPs and / or BWP pairs, (2) whether the SR was actually transmitted in the original BWP at the PHY, and / or (3) the channel occupancy status on the original DL BWP (e.g., based on it). If the WTRU 102 cancels the previous pending SR, the WTRU 102 can reset (e.g., further reset) the SR attempt counter when switching BWPs / sub - bands.

[0202] For examples of NR licenses, the WTRU 102 can cancel the pending SR when transmitting and / or after transmitting a MAC PDU that includes or contains a BSR MAC CE. For NR - U, the WTRU 102 can cancel the pending SR when transmitting a MAC PDU that includes or contains a BSR MAC CE, and after LBT has succeeded, e.g., upon receiving a notification indicating LBT success, or when it is determined that no LBT failure indication has been received from the PHY (e.g., L1 or physical layer) for an SR transmission attempt, when the grant has been confirmed by the PHY to be transmitted on the PUSCH, and / or after the confirmation. Similarly, the WTRU 102 can cancel the pending BSR when transmitting and / or after transmitting a MAC PDU that includes or contains the relevant BSR MAC CE, and after LBT has succeeded, when the grant has been confirmed by the PHY (e.g., L1 or physical layer) to be transmitted on the PUSCH, and / or after the confirmation.

[0203] - Representative procedures for multiple simultaneous LBT attempts- For example, it may be beneficial to attempt several LBTs on different resources and perhaps in different sub - bands (each having its own LBT procedure) when and / or after triggering an SR. This diversity can provide robustness against the failure to acquire a channel in one or more sub - bands. Attempting multiple LBTs can further depend on any of the following, namely: (1) the SR re - transmission count, (2) the SR attempt count, (3) the indexes of the UL BWP and DL BWP, and / or (for example, if configured and / or active) the linkage between the UL BWP and the DL BWP, (4) whether a timer (e.g., the BWP inactivity timer) is running or has expired, (5) the observed channel occupancy / loading state on the monitored sub - band / BWP, (6) a certain static or semi - static configuration, e.g., by RRC or SI, and / or (7) the capabilities of the WTRU 102 to support multiple active BWPs. The WTRU 102 can further monitor the PDCCH on multiple BWPs or sub - bands (e.g., a certain BWP or sub - band) when transmitting an SR, which can depend on the configuration and / or whether the WTRU 102 enables multiple active BWPs or BWP pairs.

[0204] - Representative configured grant transmission- The WTRU102 can be configured to have the ability to perform grant - free transmissions by using configured grants. The WTRU102 can perform LBT before transmitting with a configured grant. In some cases, the LBT may fail, and the WTRU102 may have to wait until a future configured grant occasion or a scheduled grant to transmit the WTRU102's data, and / or may have to wait, for example, it may add an undesirable waiting time. The WTRU102 can be configured to use conditionally - configured grant resources. Such conditionally - configured grant resources can be used (or can only be used) if, for example, due to a failed LBT, the previous (or immediately preceding) configured grant was not used by the WTRU102. To use a conditionally - configured grant, the WTRU102 can be configured to first receive a trigger signal from a network entity (e.g., gNB180) indicating that the conditionally - configured grant is valid. The WTRU102 can perform LBT (before or after receiving the trigger signal for the conditionally - configured grant) in a similar manner as described herein for PRACH triggers.

[0205] Figure 6 is a flowchart illustrating an exemplary procedure for using one or more unlicensed frequency bands.

[0206] Referring to FIG. 6, a representative procedure 600 can be performed by the WTRU 102 to perform system access using one or more of the unlicensed frequency bands. In block 610, the WTRU 102 can obtain LBT information indicating an LBT configuration that includes parameters applicable to the transmission of a random access (RA) preamble (RAP). In block 620, the WTRU 102 can determine, based on the LBT configuration, whether one or more respective unlicensed frequency bands of the unlicensed frequency band, or an unlicensed channel among a plurality of unlicensed channels, are available for transmission. In block 630, the WTRU 102 can transmit a RAP via a RA channel (RACH) using each unlicensed frequency band or unlicensed channel, provided that each unlicensed frequency band or unlicensed channel is available for transmission.

[0207] In certain representative embodiments, the WTRU can determine any of (1) that an uplink transmission is required, (2) that a random access procedure has been initiated, or (3) that a scheduling request is pending, and in accordance with this determination, monitor for the presence of information (e.g., LBT information and / or CTT information).

[0208] In certain representative embodiments, the WTRU 102 can set the indicated parameters and transmit a RAP in accordance with the set parameters.

[0209] In one representative embodiment, the WTRU can receive LBT information from a network entity (e.g., gNB 180), receive information associated with a plurality of LBT configurations from the network entity, and select one of the plurality of LBT configurations as the selected LBT configuration and / or select one of a plurality of pre-determined LBT configurations as the selected LBT configuration.

[0210] In one representative embodiment, the WTRU 180 can monitor a preamble transmission trigger (PTT) and / or the LBT configuration can be selected according to whether the PTT is received.

[0211] In one representative embodiment, the PTT can indicate a valid RACH resource for transmitting a RAP and / or can be either an explicit trigger or an implicit trigger based on a transmission from a network entity including (i) one or more system synchronization blocks (SSBs), (ii) one or more reference signals (RSs), (iii) one or more control channels (CCHs), (iv) one or more master information blocks (MIBs), and / or (v) one or more system information blocks (SIBs).

[0212] In one representative embodiment, the PTT can indicate one or more acceptable purposes for which RACH resources can be used therefor.

[0213] In one representative embodiment, the monitoring of the PTT can include the WTRU 102 that monitors the current PTT among a plurality of PTTs. For example, the WTRU 102 that determines whether each unlicensed frequency band or unlicensed channel is available for transmission can determine whether each unlicensed frequency band or unlicensed channel is available for a current transmission or a current retransmission on the unlicensed frequency band or unlicensed channel according to the LBT configuration selected based on the current PTT.

[0214] In one representative embodiment, the PTT can be included within a random access response (RAR).

[0215] In one representative embodiment, using co-time operation (COT), after the WTRU 102 determines that each unlicensed frequency band or unlicensed channel is available, it can acquire each unlicensed frequency band or unlicensed channel for communication with a network entity (e.g., gNB 108 or network access point (NAP)) and complete a random access channel (RACH) operation (or a series of RACH operations). The WTRU 102 can maintain each acquired unlicensed frequency or unlicensed channel for communication with the network entity while completing the RACH procedure (or e.g., a series of RACH operations). After completing the RACH procedure (or e.g., a series of RACH operations), the WTRU 102 can release each acquired unlicensed frequency band or unlicensed channel. For example, the WTRU 102 can share the unlicensed frequency band or unlicensed channel with the network entity while completing the RACH procedure (or e.g., a series of RACH operations) based on a predetermined series of transmissions between the WTRU and the network entity.

[0216] COT sharing for RACH is disclosed, but the COT sharing can be used with other types of procedures / operations, including SR operations / procedures and other control signaling procedures / operations. For example, since the WTRU can acquire an unlicensed band or channel and share it over a long duration, the WTRU can initially perform only the LBT operation and not perform another LBT while completing the RACH procedure (or series of RACH operations) and during any other possible series of transmissions.

[0217] In one representative embodiment, the WTRU 102 can perform either (1) a short LBT operation or (2) a long LBT operation.

[0218] In one representative embodiment, the WTRU 102 can monitor for a response and / or, as a result of the determination, determine whether to extend, pause, or reset the expiration time of a timer based on any of (1) whether a response should be received over or on an unlicensed frequency band or unlicensed channel, (2) whether the unlicensed frequency band or unlicensed channel is busy, and / or (3) whether the network entity did not acquire the unlicensed frequency band or unlicensed channel. The WTRU 102 can extend, pause, or reset the timer according to the determined result. For example, the WTRU 102 can retransmit the RA preamble on the condition that the timer expires before the response is received.

[0219] In one representative embodiment, the WTRU 102 can adjust either the RA response timer and / or the contention resolution timer according to the channel occupancy state.

[0220] In one representative embodiment, the WTRU 102 can monitor a random access response (RAR), can send a first message, and can monitor a second message such that the RAP, RAR, first message, and second message can be sent and / or received on different resources, each using a different LBT operation.

[0221] In one representative embodiment, the WTRU 102 can apply a backoff value to a backoff timer according to a pre-set value that depends on one or more channel occupancy states.

[0222] In one representative embodiment, after transmitting the RAP, the WTRU 102 can determine that the random access response was not sent by a network entity (e.g., gNB or network access point) on an unlicensed frequency band or unlicensed channel. The WTRU 102 can detect that the unlicensed frequency band or unlicensed channel is available and can start a backoff timer. For example, the WTRU 102 can retransmit the RAP when the backoff timer expires.

[0223] In one representative embodiment, conditioned upon the WTRU determining that the unlicensed frequency band or unlicensed channel is busy, or the network entity (e.g., gNB 180 or network access point) being unable to acquire the unlicensed frequency band, the WTRU 102 can adjust, pause, or stop the backoff timer. For example, the WTRU 102 can adjust the backoff timer using a random backoff value to provide a random backoff delay when the unlicensed frequency band or unlicensed channel becomes available again.

[0224] In one representative embodiment, after (1) acquiring an unlicensed frequency band for RAP or (2) failing to receive an RA response, the WTRU 102 can retransmit the RAP on any of different sub-bands, different interlaces, and / or different preambles / RA channel RACH occasions.

[0225] In one representative embodiment, the WTRU 102 can determine an RA priority and / or can set any of a selected LBT window and / or a configuration for non-differentiated RA based on the determined RA priority.

[0226] In one representative embodiment, the WTRU 102 can skip or apply different LBT configurations prior to transmitting a first message based on a configured or transmitted handover point.

[0227] FIG. 7 is a flowchart illustrating another representative procedure that uses one or more unlicensed frequency bands.

[0228] Referring to FIG. 7, representative procedure 700 can be performed by the WTRU 102 to perform system access using one or more unlicensed frequency bands. At block 710, the WTRU 102 can monitor a preamble transmission trigger (PTT) from a network entity (e.g., gNB or NAP) indicating that an unlicensed frequency band or unlicensed channel is available. At block 720, the WTRU 102 can transmit a random access preamble (RAP) via an available unlicensed frequency band or unlicensed channel. For example, the PTT can indicate a valid RACH resource for transmitting the RAP and can be either (1) an explicit trigger or (2) an implicit trigger.

[0229] In one representative embodiment, the WTRU 102 can provide (e.g., use) a plurality of predetermined listen before talk (LBT) operations. The WTRU 102 can determine whether an LBT operation is to be performed, and conditional upon the LBT operation being performed, the WTRU 102 can select one of the plurality of LBT operations based on the received PTT. The WTRU 102 can confirm, based on the selected LBT operation, that an unlicensed frequency band or unlicensed channel is available prior to transmitting the RAP.

[0230] In one representative embodiment, the selected LBT operation can have looser requirements for availability than when the PTT is not received.

[0231] In one representative embodiment, prior to monitoring for the PTT, the WTRU 102 can determine that the WTRU is to perform system access. The WTRU 102 can set a backoff timer and wait for the PTT to be received. Conditional upon the backoff timer expiring before the PTT is received, the WTRU 102 can extend or reset the backoff timer. Conditional upon the PTT being received before the backoff timer expires, the WTRU 102 can transmit the RAP via or on an available unlicensed frequency band or unlicensed channel.

[0232] FIG. 8 is a flowchart illustrating a further representative procedure that uses one or more unlicensed frequency bands.

[0233] Referring to FIG. 8, an exemplary procedure 800 can be performed by a WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands. At block 810, the WTRU 102 can determine whether an uplink channel in the unlicensed frequency band is available for transmission. At block 820, conditional upon the uplink channel being available for transmission, the WTRU 102 can generate a first scheduling request (SR) for SR operation and can transmit the first SR to a network entity (e.g., gNB 180 or NAP). At block 830, the WTRU 102 can start a prohibit timer to prohibit further SR operation until the expiration of a first time period. At block 840, after transmitting the first SR, the WTRU 102 can determine whether a downlink channel in the unlicensed frequency band is available for transmission by a network entity (e.g., gNB 180 or NAP). At block 850, conditional upon the downlink channel not being available for transmission by a network entity (e.g., gNB 180 or NAP), the WTRU 102 can extend the expiration of the prohibit timer and can wait for a response from the network entity (e.g., gNB 180 or NAP) for the first SR for a further time period.

[0234] In one representative embodiment, the WTRU 102 can receive an uplink grant from a network entity before the expiration of a further time period. After receiving the uplink grant, the WTRU 102 can determine whether the uplink channel is available for transmission. Conditional upon the uplink channel being available for transmission, the WTRU 102 can transmit buffer status report (BSR) information over or on the uplink channel. A higher layer of the WTRU 102 can cancel the first SR conditional upon (1) the BSR information having been transmitted by the physical layer (e.g., a lower layer) and / or (2) an indication that the LBT operation for uplink channel transmission was successful having been received from the physical layer.

[0235] In one representative embodiment, conditional upon a prohibited timer having expired after either the first time period or a further time period, the WTRU 102 can initiate a further SR operation by determining whether an unlicensed frequency band uplink channel or another uplink channel is available for transmission, and conditional upon the uplink channel or other uplink channel being available for transmission, (1) generate a further SR for the further SR operation and / or (2) transmit the further SR to a network entity.

[0236] FIG. 9 is a flowchart illustrating additional representative procedures using one or more unlicensed frequency bands.

[0237] Referring to FIG. 9, an exemplary procedure 900 can be performed by a WTRU 102 to execute system access, for example, using one or more of the unlicensed frequency bands. At block 910, the WTRU 102 can determine whether an uplink channel in the unlicensed frequency band is available for transmission. At block 920, conditional on the uplink channel being available for transmission, the WTRU 102 can generate a first scheduling request (SR) for a first SR operation and can transmit the first SR to a network entity. At block 930, the WTRU 102 can start a prohibit timer to prohibit further SR operations until the expiration of a first time period. At block 940, the WTRU 102 can receive an uplink grant from the network entity before the expiration of the first time period. At block 950, after receiving the uplink grant, the WTRU 102 can determine whether the uplink channel is available for transmission. At block 960, conditional on the uplink channel being unavailable for transmission, the WTRU 102 can extend the expiration of the prohibit timer and wait for a further uplink grant from the network entity for a further time period. At block 970, the WTRU 102 can receive a further uplink grant from the network entity by the WTRU before the expiration of the further time period.

[0238] In one representative embodiment, after receiving a further uplink grant, the WTRU 102 can determine whether an uplink channel is available for transmission. Conditioned upon the uplink channel being available for transmission, the WTRU 102 can transmit buffer status report (BSR) information over the uplink channel. A higher layer of the WTRU 102 can cancel the first SR conditioned upon the BSR information being transmitted by the physical layer (e.g., a lower layer or lowest layer) and an indication that the LBT operation for uplink channel transmission was successful being transmitted from the physical layer.

[0239] FIG. 10 is a flowchart showing exemplary further procedures for performing system access using, for example, one or more unlicensed frequency bands.

[0240] Referring to FIG. 10, an exemplary procedure 1000 can be performed by the WTRU 102 using one or more of the unlicensed frequency bands. In block 1010, the WTRU 102 can determine whether any of a plurality of sub-bands and / or bandwidth parts (BWPs) are available for transmission. In block 1020, conditioned upon two or more of the plurality of sub-bands and / or bandwidth parts being available for transmission, the WTRU 102 can attempt one or more LBT procedures (e.g., simultaneously, almost simultaneously, or sequentially) on available resources to transmit a random access preamble or a scheduling request over the available sub-bands and / or bandwidth parts. In block 1030, the WTRU 102 can receive a response to the transmission from the WTRU from a network entity over any of the plurality of sub-bands or bandwidth parts.

[0241] In one representative embodiment, after receiving a response, the WTRU 102 can determine whether any of a plurality of sub-bands or bandwidth parts are available for transmission by the WTRU. For example, conditioned upon two or more of the plurality of sub-bands or bandwidth parts being available for transmission, the WTRU 102 can transmit a message via or on two or more of the available sub-bands or bandwidth parts.

[0242] In one representative embodiment, the transmission of simultaneous or nearly simultaneous random access preambles via available sub-bands or bandwidth parts can further be conditioned upon any of (1) the preamble retransmission count, (2) the radio resource control (RRC) configuration, (3) the preamble trial count, (4) the indexes of the uplink (UL) bandwidth part and the downlink (DL) bandwidth part, (5) the linkage between the UL bandwidth part and the DL bandwidth part, (6) whether the bandwidth part inactivity timer is running, (7) the observed channel occupancy and / or load condition on the sub-band and / or bandwidth part, (8) one or more specific configurations received via signaling, and / or (9) the WTRU's ability to support a plurality of active bandwidth parts.

[0243] FIG. 11 is a flowchart showing further exemplary procedures for performing system access using, for example, one or more unlicensed frequency bands.

[0244] Referring to FIG. 11, a representative procedure 1100 can be performed by the WTRU 102 using one or more of the unlicensed frequency bands. In block 1110, the WTRU 102 can determine whether a first sub-band or a first bandwidth part of the unlicensed frequency band is available for transmission or retransmission. In block 1120, conditional on the first sub-band or the first bandwidth part being available for transmission, the WTRU 102 can transmit a random access preamble via the available first sub-band or the available first bandwidth part. In block 1130, the WTRU 102 can increment a preamble trial counter after each determination of unavailability. In block 1140, conditional on the trial counter reaching a threshold level, the WTRU 102 can determine whether a second sub-band or a second bandwidth part is available for transmission or retransmission. In block 1150, conditional on the second sub-band or the second bandwidth part being available for transmission, the WTRU 102 can switch to the second available channel and / or transmit a random access preamble via the available second sub-band or the available second bandwidth part.

[0245] In one representative embodiment, conditional on the channel not being available for transmission or retransmission, a lower layer of the WTRU 102 can report the problem to a higher layer.

[0246] In one representative embodiment, the WTRU 102 can determine whether a first sub-band or a first bandwidth part is available for transmission or retransmission. For example, the WTRU 102 can transmit a random access preamble via and / or on any of the available first and second sub-bands and / or the first and second bandwidth parts.

[0247] Figure 12 is a flowchart showing a representative procedure for selecting an LBT configuration.

[0248] Referring to Figure 12, the representative procedure 1200 can be performed by the WTRU 102 using one or more of the unlicensed frequency bands. In block 1210, the WTRU 102 can receive uplink channel transmission trigger (UCTT) information in a downlink message. In block 1220, the WTRU 102 can select the type of LBT configuration to be performed based on the received UCTT information. In block 1230, the WTRU 102 can determine whether an unlicensed frequency uplink channel is available for transmission according to the selected LBT configuration. In block 1240, conditional on the unlicensed frequency uplink channel being available for transmission according to the selected LBT configuration, the WTRU 102 can transmit data or control information via or on the unlicensed frequency uplink channel.

[0249] In one representative embodiment, the selected LBT configuration can indicate for the unlicensed frequency uplink channel that (1) a full LBT operation will be performed, (2) a shortened LBT operation will be performed, and / or (3) no LBT operation will be performed.

[0250] In one representative embodiment, the UCTT information can indicate at least the uplink control channel resources for transmitting control information, and can include any of the downlink control signals received on the downlink control channel, received in the common search space, and / or received in the WTRU-specific search space. The UCTTI can indicate any of (1) the type of UCI transmitted on the uplink channel, (2) an index for one or more valid resources for the uplink channel, and / or (3) the transmission time associated with the uplink channel.

[0251] In one representative embodiment, the control information can be a scheduling request (SR), and the WTRU 102 can transmit the SR using a first set of uplink channel resources not indicated by the UCTT information and a second set of uplink channel resources indicated by the UCTT information.

[0252] In one representative embodiment, the control information can be a scheduling request (SR), and the WTRU 102 can transmit the SR using a first set of uplink channel resources indicated by a first resource index and a second set of uplink channel resources indicated by a second resource index in accordance with the UCTT information.

[0253] FIG. 13 is a flowchart illustrating an exemplary procedure for retransmission after a failure of the LBT operation.

[0254] Referring to FIG. 13, a representative procedure 1300 can be performed by the WTRU 102 using one or more of the unlicensed frequency bands. In block 1310, the WTRU 102 can determine whether a channel (e.g., a first sub-band or a first bandwidth part of one or more unlicensed frequency bands) is available for transmission. In block 1320, conditional upon the channel being available for transmission, the WTRU 102 can transmit a scheduling request (SR) over or on the available channel. In block 1330, the WTRU 102 can increment a trial counter after each determination of unavailability. In block 1340, conditional upon the trial counter reaching a threshold level, the WTRU 102 can determine any of (1) whether to determine whether additional channels are available and switch to them, (2) whether to transmit an SR on an additional channel, (3) whether to initiate a random access procedure on an additional channel, (3) whether to report the problem to a higher layer, and / or (4) whether to change the LBT configuration used. In block 1350, conditional upon the WTRU determining to retransmit an SR or an RA-SR on an additional channel, the WTRU 102 can determine whether the additional channel is available. In block 1360, the WTRU 102 can retransmit an SR or an RA-SR over or on the additional channel.

[0255] FIG. 14 is a flowchart showing a representative procedure using a preamble trigger.

[0256] Referring to FIG. 14, a representative procedure 1400 can be implemented by the WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands. At block 1410, the WTRU 102 can monitor a preamble transmission trigger (PTT). At block 1420, conditioned on the PTT being received, the WTRU 102 can transmit a random access preamble (RAP) via or on each of one or more unlicensed frequency bands.

[0257] In one representative embodiment, the WTRU 102 can monitor each unlicensed band to determine whether each unlicensed band is available for transmission and / or, based on the WTRU monitoring, after determining that an unlicensed frequency band is available, conditioned on the PTT being received, transmit a RAP via or on the unlicensed frequency band. For example, the monitoring of each unlicensed frequency band can include continuous or periodic monitoring of each unlicensed frequency band. The WTRU 102 can determine whether each unlicensed band is available for transmission by performing one or more LBT operations.

[0258] FIG. 15 is a flowchart illustrating a representative procedure that uses a selected beam.

[0259] Referring to FIG. 15, a representative procedure 1500 can be performed by the WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands and a selected beam among a plurality of candidate beams. In block 1510, the WTRU 102 can map each beam among a plurality of candidate beams, each associated with a system synchronization block, to a respective set of PRACH resources or to a respective random access preamble (RAP). In block 1520, the WTRU 102 can determine the selected beam from among the mapped beams. In block 1530, the WTRU 102 can determine whether each unlicensed frequency band among one or more unlicensed frequency bands is available for transmission. In block 1540, conditioned that each unlicensed frequency band is available for transmission, the WTRU 102 can transmit the RAP via the PRACH using each unlicensed frequency band and the selected beam.

[0260] In one representative embodiment, conditioned that each unlicensed frequency band is not available for transmission, the WTRU 102 can remap a portion of the beams among a plurality of candidate beams, each associated with a system synchronization block, to the same or a different set of PRACH resources or to the same or a different random access preamble (RAP), and / or can determine a newly selected beam from among the remapped beams. The WTRU 102 can determine whether each unlicensed frequency band among one or more unlicensed frequency bands is available for transmission. Conditioned that each unlicensed frequency band is available for transmission, the WTRU 102 can transmit the same RAP or another RAP via or on the PRACH using each unlicensed frequency band and the newly selected beam.

[0261] In one representative embodiment, conditioned on each unlicensed frequency band being unavailable for transmission, the WTRU 102 can select a new unlicensed frequency band from among one or more unlicensed frequency bands and / or can determine whether a new unlicensed frequency band is available for transmission. Conditioned on the new unlicensed frequency band being available for transmission, the WTRU 102 can transmit the same RAP or a different RAP via or on the PRACH using the new unlicensed frequency band and the selected beam.

[0262] In one representative embodiment, conditioned on each unlicensed frequency band being unavailable for transmission, the WTRU 102 can wait for the next RACH occasion. The WTRU 102 can determine whether each unlicensed frequency band among one or more unlicensed frequency bands is available for transmission during the next RACH occasion. Conditioned on each unlicensed frequency band being available for transmission, after remapping, the WTRU 102 can transmit a RAP via or on the RACH using each unlicensed frequency band and the selected beam or another beam.

[0263] In one representative embodiment, the determination of the selected beam or newly selected beam can include the WTRU 102 receiving downlink information including a plurality of synchronization signal blocks (SSBs) and determining the selected beam based on one or more signal characteristics of one of the SSBs of the plurality of SSBs associated with the selected beam.

[0264] FIG. 16 is a flowchart illustrating a representative procedure using an interference threshold.

[0265] Referring to FIG. 16, a representative procedure 1600 can be performed by the WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands. At block 1610, the WTRU 102 can determine, via the LBT operation, whether each of one or more of the unlicensed frequency bands is available for transmission. At block 1620, conditional upon each unlicensed frequency band being available for transmission, the WTRU 102 can transmit a RAP via or on the PRACH using each of one or more of the unlicensed frequency bands. For example, determining whether each unlicensed frequency band is available for transmission can include performing a clear channel assessment (CCA), as part of the LBT operation, that includes the WTRU 102 setting an interference threshold for PRACH transmission that is different from the interference threshold for other transmissions.

[0266] In one representative embodiment, the interference thresholds for PRACH transmission and other transmissions, used for CCA, vary over the course of the LBT operation.

[0267] In one representative embodiment, the WTRU 102 can receive an LBT configuration that can include, or indicate, a variable CCA threshold and / or a variable timing offset between the end of the LBT operation and the start of RAP transmission on the PRACH.

[0268] In one representative embodiment, the WTRU 102 can determine that (1) each unlicensed frequency band is available prior to a time determined by an offset and the timing of RAP transmission on the PRACH, or (2) each unlicensed frequency band is not available.

[0269] Figure 17 is a flowchart illustrating an exemplary procedure using a selected LBT operation.

[0270] Referring to Figure 17, an exemplary procedure 1700 can be performed by the WTRU 102 to execute system access, for example, using one or more of the unlicensed frequency bands. At block 1710, the WTRU 102 can determine, as a result of the determination, whether it can transmit an uplink transmission in the same slot and / or the same symbol as another uplink transmission from another WTRU. At block 1720, the WTRU 102 can select an LBT operation from a set of candidate LBT operations based on the determined result, and the selected LBT operation can be different from other candidate LBT operations in either (1) the type of LBT operation or (2) the LBT parameters used in the LBT operation. At block 1730, the WTRU 102 can determine, via the selected LBT operation, whether each of one or more of the unlicensed frequency bands is available for transmission. At block 1740, conditional upon the unlicensed frequency band being available for transmission, the WTRU 102 can transmit a RAP via or on the PRACH using each unlicensed frequency band.

[0271] Figure 18 is a flowchart illustrating an exemplary procedure using interleaving information.

[0272] Referring to FIG. 18, a representative procedure 1800 can be performed by the WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands. In block 1810, the WTRU 102 can acquire either (1) the interlace information transmitted by the network entity or (2) the preconfigured interlace rule information. In block 1820, the WTRU 102 can map either the PUSCH and / or PRACH of the WTRU to the time / frequency elements in each of the one or more unlicensed frequency bands such that the PUSCH and / or PRACH of the WTRU will be interlaced with the uplink information of one or more other WTRUs, based on the acquired information. In block 1830, the WTRU 102 can transmit the PUSCH and / or PRACH channels on the mapped time / frequency elements of each of the unlicensed frequency bands.

[0273] In certain representative embodiments, (1) the PUSCH can be interlaced and the PRACH cannot be interlaced, (2) the PUSCH and PRACH can be transmitted using different interlaces, and / or (3) the PUSCH and PRACH can be transmitted using a single interlace.

[0274] FIG. 19 is a flowchart illustrating a representative procedure using a conditional grant indicator.

[0275] Referring to FIG. 19, a representative procedure 1900 can be performed by the WTRU 102 to perform system access, for example, using one or more of the unlicensed frequency bands. In block 1910, the WTRU 102 can transmit a RAP via or on the PRACH using each of one or more of the unlicensed frequency bands. In block 1920, the WTRU 102 can receive a grant for an uplink resource associated with each of the unlicensed frequency bands. In block 1930, the WTRU 102 can determine whether each of the unlicensed frequency bands associated with the grant is available for transmission. In block 1940, the WTRU 102 can (1) transmit uplink communication using each of the unlicensed frequency bands, conditioned on each of the unlicensed frequency bands being available for transmission, or (2) transmit uplink communication using each of the unlicensed frequency bands when each of the unlicensed frequency bands becomes available, conditioned on a conditional grant indicator being set.

[0276] FIG. 20 is a flowchart illustrating a representative procedure for using channels.

[0277] Referring to FIG. 20, a representative procedure 2000 can be performed by the WTRU 102 using one or more channels in, for example, one of the unlicensed frequency bands. In block 2010, the WTRU 102 can receive a channel transmission trigger (CTT) in a downlink message. In block 2020, the WTRU 102 can select a type of listen before talk (LBT) configuration to be performed based on the received CTT. In block 2030, the WTRU 102 can determine whether the channel is available for transmission according to the selected type of LBT configuration. In block 2040, conditioned that the channel is available for transmission, the WTRU 102 can transmit data or control information on the channel.

[0278] In one representative embodiment, the selection of the type of LBT configuration to be performed can further be based on either (1) the content of the CTT and / or (2) the timing of CTT reception and the timing of the corresponding uplink transmission.

[0279] In one representative embodiment, the WTRU 102 can determine the LBT configuration implicitly based on the time difference between CTT reception and the start of uplink transmission or explicitly from the CTT content.

[0280] In one representative embodiment, the WTRU 102 can determine that transmission is required and, after determining that transmission is required, can monitor for the presence of a CTT.

[0281] In one representative embodiment, the channel can be any of (1) one or more frequency bands, (2) one or more component carriers, (3) one or more bandwidth parts, (4) one or more subbands, (5) one or more LBT bandwidths, and / or (6) time / frequency resources.

[0282] In one representative embodiment, the selected type of LBT configuration can indicate, for a channel, one of (1) that a full LBT operation will be performed, (2) that a shortened LBT operation will be performed, or (3) that no LBT operation will be performed.

[0283] In one representative embodiment, the CTT can indicate at least uplink control channel resources for transmitting control information, and / or the CTT can include downlink control information received by the WTRU in a common search space or in a WTRU-specific search space.

[0284] In one representative embodiment, the CTT can indicate any of (1) the type of UCI transmitted on the channel, (2) an index to one or more valid resources for the channel, (3) the transmission time associated with the channel, and / or (4) the LBT configuration applicable to uplink transmission after reception of the CTT.

[0285] In one representative embodiment, the control information is a scheduling request (SR), and / or transmitting the SR on the channel can include transmitting the SR using a first set of channel resources not indicated by the CTT or using a second set of channel resources indicated by the CTT.

[0286] In one representative embodiment, the WTRU 102 can obtain LBT information including at least a first type of LBT configuration and a second type of LBT configuration. For example, the first type of LBT configuration can be an LBT configuration for a shortened LBT operation, the second type of LBT configuration can be an LBT configuration for a full LBT operation, and / or the third type of LBT configuration can be an LBT configuration for no LBT operation.

[0287] In one representative embodiment, the control information can include a Random Access Preamble (RAP) or Message 3 that is used in a random access procedure. The CTT can indicate, for example, a Random Access Channel (RACH) resource for transmitting the RAP, and / or the CTT can be either (1) an explicit trigger or (2) an implicit trigger based on transmissions from a network entity that includes (i) one or more System Synchronization Blocks (SSBs), (ii) one or more Reference Signals (RSs), or (iii) one or more Downlink Control Channels (DCCHs).

[0288] In one representative embodiment, the CTT can indicate one or more acceptable purposes for which the RACH resource can be used therefor.

[0289] FIG. 21 is a flowchart illustrating another representative procedure for using a channel.

[0290] Referring to FIG. 21, the representative procedure 2100 can be performed by the WTRU102 using one or more channels of an unlicensed frequency band, for example. In block 2110, the WTRU102 can determine whether a preamble transmission or a scheduling request transmission attempt has failed the LBT operation for a first channel. In block 2120, the WTRU102 can increment a preamble / SR trial counter for each trial failure. Conditional on the trial counter reaching a threshold level, in block 2130, the WTRU102 can (1) perform a switch to a further channel, (2) transmit an SR on the further channel, (3) initiate a random access procedure on the further channel, (4) report the problem to a higher layer, and / or (5) change the LBT configuration used. For example, the further channel can be different from the first channel.

[0291] In one representative embodiment, the first channel can be any of (1) a first set of one or more frequency bands, (2) a first set of one or more component carriers, (3) a first set of one or more bandwidth parts, (4) a first set of one or more subbands, (5) a first set of one or more LBT bandwidths, (6) a first cell, (7) a first set of physical layer characteristics, and / or (8) a first set of time / frequency resources.

[0292] In one representative embodiment, a further channel can be any of (1) a second set of one or more frequency bands, (2) a second set of one or more component carriers, (3) a second set of one or more bandwidth parts, (4) a second set of one or more subbands, (5) a second set of one or more LBT bandwidths, (6) a second cell, (7) a second set of physical layer characteristics, and / or (8) a second set of time / frequency resources.

[0293] In one representative embodiment, determining whether a preamble transmission or SR transmission attempt has failed the listen-before-talk (LBT) operation for the first channel can include determining the number of failed LBT attempts for the first channel, where a trial counter is incremented after each LBT attempt failure until the trial counter reaches a threshold level, and before the trial counter reaches the threshold level, the LBT operation is repeatedly attempted on the first channel, and after the trial counter reaches the threshold level, the LBT operation is likely repeatedly attempted on a further channel.

[0294] FIG. 22 is a flowchart showing a further representative procedure using channels.

[0295] Referring to FIG. 22, a representative procedure 2200 can be performed by the WTRU 102, for example, using one or more additional channels in an unlicensed frequency band. In block 2210, the WTRU 102 can determine that the first channel is not available for transmission or retransmission and that additional channels are available for transmission or retransmission. In block 2220, the WTRU 102 can switch to an additional available channel for preamble transmission or retransmission.

[0296] In one representative embodiment, the first channel can be any of (1) a first set of one or more frequency bands, (2) a first set of one or more component carriers, (3) a first set of one or more bandwidth parts, (4) a first set of one or more subbands, (5) a first set of one or more cells, or (6) a first set of one or more time / frequency resources, and the additional channel can be any of (1) a further set of one or more frequency bands, (2) a further set of one or more component carriers, (3) a further set of one or more bandwidth parts, (4) a further set of one or more subbands, or (5) a further set of one or more time / frequency resources.

[0297] In one representative embodiment, the preamble can be a random access (RA) preamble for an ongoing RA procedure or a newly initiated procedure.

[0298] In one representative embodiment, the determination of whether an additional channel is available for transmission or retransmission can further be conditioned on whether a availability trial counter has reached a configured threshold.

[0299] FIG. 23 is a flowchart illustrating an additional representative procedure using channels.

[0300] Referring to FIG. 23, a representative procedure 2300 can be performed by the WTRU 102 using, for example, one or more channels in an unlicensed frequency band. In block 2310, the WTRU 102 can perform an LBT operation to determine whether the channel is available for transmission. In block 2320, conditional on the channel not being available, the WTRU 102 can apply a random backoff to a backoff timer immediately or after the channel becomes available, wait for the expiration of the backoff timer, and transmit on the channel after the expiration of the backoff timer.

[0301] FIG. 24 is a flowchart showing another representative procedure for using a channel.

[0302] Referring to FIG. 24, a representative procedure 2400 can be performed by the WTRU 102 using, for example, two or more channels in an unlicensed frequency band. In block 2410, the WTRU 102 can determine whether two or more channels are available for possible transmission. In block 2420, conditional on a plurality of the two or more channels being available for possible transmission, the WTRU 102 can initiate a plurality of LBT attempts to transmit control information on one or a subset of the available channels. In block 2430, the WTRU 102 can receive, from a network entity, a response to control information transmitted from the WTRU 102 on any of the available channels.

[0303] In one representative embodiment, two or more channels can be any of (1) one or more frequency bands, (2) one or more component carriers, (3) one or more bandwidth parts, (4) one or more cells, (5) one or more sub-bands, (6) one or more LBT bandwidths, (7) physical layer characteristics, and / or (8) time / frequency resources.

[0304] In one representative embodiment, transmitting control information on one or more available channels can include transmitting a random access preamble or a random access (RA) message (Msg3) on one or more available channels.

[0305] In one representative embodiment, receiving a response to control information on any of the available channels can include receiving a RA response (RAR) on any of the available channels.

[0306] In one representative embodiment, after receiving the RAR, the WTRU 102 can determine whether any of the two or more channels are available for transmission by the WTRU. For example, conditional on a plurality of the two or more channels being available for transmission by the WTRU, the WTRU can transmit further messages via or on the available channels.

[0307] In one representative embodiment, two or more channels can be either (1) one or more bandwidth parts, or (2) one or more sub-bands.

[0308] In one representative embodiment, the initiation of a plurality of LBT attempts to transmit a RA preamble on an available channel can be further conditioned by any of (1) the preamble retransmission count, (2) the radio resource control (RRC) configuration, (3) the preamble attempt count, (4) the indexes of the uplink (UL) bandwidth part and the downlink (DL) bandwidth part, (5) the linkage between the UL bandwidth part and the DL bandwidth part, (6) whether the inactive timer of the bandwidth part is running, (7) the observed channel occupancy, or (8) the load condition on the subband and / or bandwidth part, (9) one or more specific configurations received via signaling, and / or (10) the capabilities of the WTRU 102 to support a plurality of active bandwidth parts.

[0309] FIG. 25 is a flowchart showing a further representative procedure of using a channel.

[0310] Referring to FIG. 25, a representative procedure 2500 can be implemented by the WTRU 102 using one or more channels of an unlicensed frequency band, for example. At block 2510, the WTRU 102 can determine that the LBT operation has been successful such that the channel is available for transmission. At block 2520, the WTRU 102 can transmit a random access (RA) preamble using the channel. At block 2530, the WTRU 102 can start a timer associated with a RA window to monitor for the reception of a RA response (RAR) for the transmitted RA preamble. At block 2540, the WTRU 102 can monitor for the reception of the RAR during the RA window.

[0311] In one representative embodiment, the WTRU 102 can determine whether to extend, pause, or reset the expiration time of a timer based on any of (1) whether a RAR should be received on the channel, (2) the channel being busy, or (3) the network entity (such as gNB 180) not acquiring the channel as a determined result. For example, the WTRU can extend, pause, or reset the timer according to the determined result and / or can retransmit the RA preamble conditional on the timer expiring before receiving the RAR.

[0312] In one representative embodiment, RA preambles can be transmitted and RARs can be received on different resources, each using a different LBT operation.

[0313] FIG. 26 is a flowchart showing the use of channels and additional representative procedures.

[0314] Referring to FIG. 26, a representative procedure 2600 can be performed by the WTRU 102, for example, using one or more channels in an unlicensed frequency band. In block 2610, the WTRU 102 can determine whether a channel is available for a first transmission. In block 2620, conditional on the channel being available for the first transmission, the WTRU 102 can generate a first scheduling request (SR) for SR operation and can transmit the first SR to a network entity. In block 2630, the WTRU 102 can start an SR prohibition timer to prohibit further SR operation until the expiration of a first time period. In block 2640, the WTRU 102 can use a LBT operation to determine whether the channel or a further channel is available for a further transmission. In block 2650, the WTRU 102 can adjust the expiration of the SR prohibition timer according to the result of the LBT operation before the expiration of the SR prohibition timer. For example, the time period associated with the expiration of the SR prohibition timer can be adjusted to shorten or extend the expiration period.

[0315] FIG. 27 is a flowchart showing a further representative procedure of using a channel.

[0316] Referring to FIG. 27, a representative procedure 2700 can be performed by the WTRU 102 using one or more channels in, for example, one of the unlicensed frequency bands. In block 2710, the WTRU 102 can determine whether the channel is available for transmission. In block 2720, conditional on the channel being available for transmission, the WTRU 102 can generate a first scheduling request (SR) for SR operation and transmit the first SR to a network entity (e.g., gNB 180, or another network entity). In block 2730, the WTRU 102 can start a prohibit timer to prohibit further SR operation until the expiration of a first time period. In block 2740, after transmitting the first SR, the WTRU 102 can determine whether a channel used to receive a response to the first SR or another channel is available for transmission by the network entity. In block 2750, conditional on the channel or a further channel not being available for transmission by the network entity, the WTRU 102 can extend the expiration of the prohibit timer and wait for a response to the first SR for a further time period.

[0317] In one representative embodiment, the WTRU 102 may receive an uplink grant from the network entity before the expiration of the further time period, and after receiving the uplink grant, determine whether the channel is available for transmission with the provided uplink grant. For example, conditional on the channel being available for transmission, the WTRU 102 can transmit buffer status report (BSR) information on the channel. A higher layer of the WTRU 102 can cancel the first pending SR and the BSR conditional on (1) the BSR information being transmitted by the physical layer (as the lower layer) and (2) an indication from the physical layer that the LBT operation was successful for channel transmission.

[0318] In one representative embodiment, on condition that the prohibition timer has expired after a first time period or a further time period and before receiving a response to the first SR, the WTRU 102 can initiate a further SR operation by determining whether a channel or another channel is available for transmission. On condition that a channel or another channel is available for transmission, the WTRU 102 can (1) generate a further SR for a further SR operation and can transmit the further SR to a network entity. The WTRU 102 can start a prohibition timer to prohibit additional SR operations until another time period expires. The WTRU 102 may receive an uplink grant from the network entity before the expiration of another time period. After receiving the uplink grant, the WTRU 102 can determine whether a channel or another channel is available for transmission with the provided uplink grant. On condition that a channel or another channel is not available for transmission, the WTRU 102 can extend the expiration of the prohibition timer and wait for a further uplink grant from the network entity for a further time period. The WTRU can monitor for the reception of a further uplink grant before the expiration of the further time period.

[0319] FIG. 28 is a flowchart showing still additional representative procedures for using channels.

[0320] Referring to FIG. 28, a representative procedure 2800 can be performed by the WTRU 102 using one or more channels in, for example, one of the unlicensed frequency bands. At block 2810, the WTRU 102 can determine from signaling sent by a network entity (1) that a Channel Occupancy Time (COT) sharing operation is being performed on a channel acquired by the network entity, and (2) one or more switching points at which the WTRU is to transmit on the channel acquired by the network entity. At block 2820, the WTRU 102 can determine the type of LBT configuration to be performed based on the COT sharing operation and the current switching point of one or more determined switching points. At block 2830, according to the selected type of LBT configuration, the WTRU 102 can determine whether the channel is available for transmission. At block 2840, conditional on the channel being available for transmission, the WTRU 102 can transmit data or control information on the channel at the current switching point.

[0321] In one representative embodiment, the selected type of LBT configuration can indicate either (1) that a shortened LBT operation will be performed, or (3) that no LBT operation will be performed. For example, the selected type of LBT configuration can indicate a shortened LBT operation, and transmitting data or control information on the channel at the switching point can include transmitting a Random Access (RA) message on the channel at the current switching point (e.g., after completing the shortened LBT operation).

[0322] In one representative embodiment, after transmitting the RA message, the WTRU 102 can transmit data on the channel acquired by the network entity.

[0323] A system and method for processing data according to an exemplary embodiment can be executed by one or more processors that execute a series of instructions included within a memory device. Such instructions can be read into the memory device from other computer-readable media, such as a secondary data storage device. Execution of the series of instructions included within the memory device causes, for example, the processor to operate, as described above. In an alternative embodiment, a hardwired circuit can be used to implement the present invention, instead of or in combination with software instructions. Such software can operate on a processor remotely housed within a robotic assistive / device (RAA) and / or another mobile device. In the latter case, data can be transferred between the RAA, or other mobile device including a sensor, and a remote device including a processor that operates software that performs scale estimation and compensation, as described above, either wired or wirelessly. According to other exemplary embodiments, some of the processing described above with respect to location determination can be performed in a device including a sensor / camera, but the remainder of the processing can be performed in a second device after receipt of the partially processed data from the device including the sensor / camera.

[0324] Although features and elements have been described above in certain combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with other features and elements. Additionally, the methods described herein can be implemented by a computer program, software, or firmware incorporated into a computer-readable medium for execution by a computer or processor. Examples of non-transitory computer-readable storage media include, but are not limited to, magnetic media such as read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, internal hard disks, and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVD). A processor associated with software can be used to implement a radio frequency transceiver for use in a WTRU, user equipment, terminal, base station, RNC, or any host computer.

[0325] In further embodiments described above, other devices including a processing platform, computing system, controller, and processor were described. These devices can include at least one central processing unit ("CPU") and memory. In accordance with the convention of those of ordinary skill in the art in the field of computer programming, references to acts, and to operations or instructions in symbolic representation, can be performed by various CPUs and memories. Such acts, and operations or instructions are sometimes said to be "executed," "computer-executed," or "CPU-executed."

[0326] One of ordinary skill in the art will understand that actions, and symbolic representations of actions or instructions, include the manipulation of electrical signals by a CPU. An electrical system represents data bits, which can cause the conversion or reduction of the resulting electrical signals and the maintenance of the data bits at a memory location within a memory system, thereby restructuring or otherwise changing the operation of the CPU and other processing of the signals. The memory location where the data bits are maintained is a physical location having specific electrical, magnetic, optical, or organic characteristics corresponding to or representing the data bits. Representative embodiments are not limited to the platforms or CPUs mentioned above, and it should be understood that other platforms and CPUs can support the provided methods.

[0327] Data bits can also be maintained on a computer-readable medium, including magnetic disks, optical disks, and any other volatile (e.g., random access memory (“RAM”)) or non-volatile (e.g., read-only memory (“ROM”)) mass storage systems readable by a CPU. The computer-readable medium can include cooperative or interconnected computer-readable media, which are distributed among multiple interconnected processing systems that can exist exclusively on a processing system or can be local or remote to the processing system. Representative embodiments are not limited to the memories mentioned above, and it is understood that other platforms and memories can support the described methods.

[0328] In an exemplary embodiment, any of the operations, processes, etc. described herein can be implemented as computer-readable instructions stored on a computer-readable medium. The computer-readable instructions can be executed by a processor of a mobile unit, network element, and / or any other computing device.

[0329] The differences remaining between the hardware implementation and the software implementation of the system aspects are few. Whether to use hardware or software is generally (but not always, as in some situations the choice between hardware and software can become important) a design choice representing a cost - efficiency trade - off. Various means (e.g., hardware, software, and / or firmware) by which the processes and / or systems and / or other technologies described herein may be affected can exist, and the preferred means may vary with the circumstances in which the processes and / or systems and / or other technologies are deployed. For example, if the implementer determines that speed and accuracy are of utmost priority, the implementer can primarily select hardware and / or firmware means. If flexibility is of utmost priority, the implementer can primarily select a software implementation. Alternatively, the implementer can select some combination of hardware, software, and / or firmware.

[0330] The foregoing detailed description has described various embodiments of devices and / or processes via the use of block diagrams, flowcharts, and / or examples. As long as such block diagrams, flowcharts, and / or examples include one or more functions and / or operations, it will be understood by those skilled in the art that each function and / or operation within such block diagrams, flowcharts, or examples can be implemented individually and / or collectively by a wide range of hardware, software, firmware, or substantially any combination thereof. Suitable processors include, by way of example, general-purpose processors, dedicated processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microprocessors, application specific integrated circuits (ASICs), application specific standard products (ASSPs), field programmable gate array (FPGA) circuits, any other type of integrated circuit (IC), and / or state machines.

[0331] Although features and elements were provided above in particular 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. The present disclosure is not to be limited with respect to the particular embodiments described in this application, which are intended as examples of various aspects. As will be apparent to those skilled in the art, many changes and modifications can be made without departing from its spirit and scope. Elements, acts, or instructions used in the description of this application should not be construed as critical or essential to the invention unless explicitly stated to be so. In addition to those listed herein, functionally equivalent methods and apparatuses within the scope of the present disclosure will be apparent to those skilled in the art from the foregoing description. Such changes and modifications are intended to be included within the scope of the appended claims. The present disclosure should be limited only by the claims of the appended claims, along with the full scope of equivalents to which such claims are entitled. It should be understood that the present disclosure is not limited to a particular method or system.

[0332] It should also be understood that the terms used in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting. As used in this specification and when referred to herein, the terms "station" and its abbreviation "STA", "user equipment" and its abbreviation "UE" can mean (i) a wireless transmit and / or receive unit (WTRU) as described below, (ii) any of the various embodiments of a WTRU as described below, (iii) a wireless and / or wireline-enabled (e.g., connectable) device configured to use some or all of the structure and functionality of a WTRU, as described below, (iv) a wireless and / or wireline-enabled device configured to use less structure and functionality than all of a WTRU, as described below, or (v) something similar. Details of exemplary WTRUs, which can represent any of the WTRUs listed herein, are provided below with respect to FIGS. 1A-1D.

[0333] In one representative embodiment, some parts of the invention described herein can be implemented via application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs), and / or other integrated formats. However, one skilled in the art will recognize that some aspects of the embodiments disclosed herein can be implemented equivalently, in whole or in part, as one or more computer programs operating on one or more computers (e.g., as one or more programs operating on one or more computer systems), as one or more programs operating on one or more processors (e.g., as one or more programs operating on one or more microprocessors), as firmware, or as substantially any combination thereof, and that designing the circuitry and / or writing the code for the software and / or firmware is well within the skill of one of ordinary skill in the art in light of the present disclosure. Additionally, one skilled in the art will understand that the mechanisms of the invention described herein can be distributed in a variety of forms as a program product, and that the exemplary embodiments of the invention described herein will apply regardless of the particular type of signal bearing medium used to actually carry out the distribution. Examples of signal bearing media include, but are not limited to, recordable type media such as floppy disks, hard disk drives, CDs, DVDs, digital tapes, computer memories, and transmission type media such as digital and / or analog communication media (e.g., optical fiber cables, waveguides, wired communication links, wireless communication links, etc.).

[0334] The present invention described herein sometimes exemplifies different components that are included within or connected to other different components. It should be understood that such depicted architectures are merely examples and that in practice many other architectures can be implemented that achieve the same functionality. In a conceptual sense, any arrangement of components for achieving the same functionality is effectively "associated" so as to be able to achieve the desired functionality. Thus, any two components herein combined to achieve a particular functionality can be seen as "associated" with each other such that the desired functionality is achieved, regardless of the architecture or intervening components. Similarly, any two components so associated can also be regarded as "operably connected" or "operably coupled" to each other for achieving the desired functionality, and any two components that can be so associated can also be regarded as "operably couplable" to each other for achieving the desired functionality. Particular examples of operably couplable include, but are not limited to, components that can be physically paired and / or physically interact, and / or wirelessly interact and / or wirelessly communicate, and / or logically interact and / or logically communicate with each other.

[0335] Regarding the use of substantially any plural and / or singular terms herein, one of ordinary skill in the art can translate from plural to singular and / or from singular to plural as appropriate to the situation and / or application. For clarity, various singular / plural substitutions may be explicitly described herein.

[0336] Generally, in this specification, and in particular in the appended claims (e.g., the body of the appended claims), it will be understood by those skilled in the art that the terms used are generally intended to be "open" terms (e.g., the term "including" should be construed as "including but not limited to", the term "having" should be construed as "having at least", the term "includes" should be construed as "including but not limited to", etc.). When a specific number of claim recitations is intended, such intent will be expressly recited in the claim, and it will be further understood by those skilled in the art that when no such recitation is present, no such intent exists. For example, when only one item is intended, the term "single" or similar words can be used. For purposes of understanding, the following appended claims and / or the description in this specification can include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim that includes such introduced claim recitation to embodiments that include only one such recitation (e.g., "a" and / or "an" should be construed as meaning "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. In addition, even when a specific number of introduced claim recitations is expressly recited, those skilled in the art will recognize that such recitation should be construed as meaning at least the recited number (e.g., an unadorned recitation of "two recitations" without other modifying phrases means at least two recitations, or two or more recitations).Furthermore, when conventional expressions similar to "at least one of A, B, and C" are used, generally, such syntax is intended in the sense that a person skilled in the art would understand the conventional expression (for example, "a system having at least one of A, B, and C" includes, but is not limited to, a system having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). When conventional expressions similar to "at least one of A, B, or C" are used, generally, such syntax is intended in the sense that a person skilled in the art would understand the conventional expression (for example, "a system having at least one of A, B, or C" includes, but is not limited to, a system having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). It will be further understood by those skilled in the art that substantially any disjunctive words and / or phrases presenting two or more alternatives, whether within the description, within the claims, or within the drawings, are intended to contemplate the possibility of including one of the terms, either of the terms, or both of the terms. For example, the phrase "A or B" is understood to include the possibilities of "A", or "B", or "A and B". Further, as used herein, the term "any of" followed by a list of multiple items and / or multiple categories of items is intended to include "any of" the items and / or categories of items, "any combination", "any plurality of", and / or "any combination of a plurality of" the items and / or categories of items, either individually or in combination with other items and / or other categories of items. Further, as used herein, the terms "set" or "group" are intended to include any number of items, including zero. Additionally, as used herein, the term "number" is intended to include any number, including zero.

[0337] In addition, when a feature or aspect of the present disclosure is described with respect to a Markush group, one of ordinary skill in the art will recognize that the present disclosure is thereby also described with respect to any individual member or subgroup of members of the Markush group.

[0338] As will be understood by one of ordinary skill in the art, for all purposes such as providing a written description, all ranges disclosed herein include any and all possible subranges, and combinations thereof. Any recited range can be readily recognized as also fully describing and enabling the same range decomposed into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range disclosed herein can be readily decomposed into lower thirds, middle thirds, and upper thirds, etc. Also as will be understood by one of ordinary skill in the art, all words such as "up to," "at least," "greater than," and "less than" include the recited number and refer to ranges that can later be divided into subranges as described above. Finally, as will be understood by one of ordinary skill in the art, ranges include each and every member. Thus, for example, a group having 1 to 3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1 to 5 cells refers to a group having 1, 2, 3, 4, or 5 cells, and so on for others.

[0339] Furthermore, the claims should not be read as being limited to the order or elements provided unless stated to that effect in the claims. In addition, the use of the term "means for" in any claim is intended to invoke 35 U.S.C. § 112, paragraph 6, or means-plus-function claim format, and any claim that does not include the term "means for" is not intended to be read as such.

[0340] A radio frequency transceiver can be implemented for use in a wireless transmit / receive unit (WTRU), user equipment (UE), terminal, base station, mobility management entity (MME) or evolved packet core (EPC), or any host computer, using a processor associated with software. The WTRU can be used in conjunction with other components, including hardware, and / or software modules implemented in software, including software defined radio (SDR), as well as cameras, video camera modules, videophones, speakerphones, vibration devices, speakers, microphones, television transceivers, hands-free headsets, keyboards, Bluetooth® modules, frequency modulation (FM) radio units, near field communication (NFC) modules, liquid crystal display (LCD) display units, organic light emitting diode (OLED) display units, digital music players, media players, video game player modules, Internet browsers, and / or wireless local area network (WLAN) or ultra wideband (UWB) modules.

[0341] Although the invention has been described with respect to a communication system, it is contemplated that the system can be implemented in software on a microprocessor / general purpose computer (not shown). In certain embodiments, one or more of the functions of the various components can be implemented in software that controls a general purpose computer.

[0342] In addition, although the invention has been illustrated and described herein with reference to particular embodiments, the invention is not intended to be limited to the details shown. Rather, various changes can be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

[0343] Those skilled in the art will understand that representative embodiments can be used in alternate or in combination with other representative embodiments throughout this disclosure.

[0344] Those skilled in the art will appreciate that, although features and elements are described above in certain combinations, each feature or element can be used alone or in any combination with other features and elements. Additionally, the methods described herein can be implemented by a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of non-transitory computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A radio frequency transceiver for use in a WTRU, WTRU, terminal, base station, RNC, or any host computer can be implemented using a processor associated with software.

[0345] Furthermore, in the embodiments described above, other devices including a processing platform, computing system, controller, and processor were described. These devices can include at least one central processing unit ("CPU") and memory. In accordance with the practice of those skilled in the art of computer programming, references to acts, and to symbolic representations of operations or instructions, can be performed by various CPUs and memories. Such acts and operations or instructions are sometimes said to be "executed," "computer-executed," or "CPU-executed."

[0346] One of ordinary skill in the art will appreciate that acts, and symbolic representations of operations or instructions, involve the manipulation of electrical signals by a CPU. An electrical system represents data bits, which can cause a resulting conversion or reduction of electrical signals and the maintenance of data bits at memory locations within a memory system, thereby restructuring or otherwise changing the operation of the CPU and other processing of the signals. The memory locations at which the data bits are maintained are physical locations having specific electrical, magnetic, optical, or organic characteristics corresponding to or representing the data bits.

[0347] Data bits can also be maintained on a computer-readable medium, including magnetic disks, optical disks, and any other volatile (e.g., random access memory (“RAM”)) or non-volatile (e.g., read only memory (“ROM”)) mass storage systems readable by a CPU. A computer-readable medium can include cooperative or interconnected computer-readable media, which can be distributed among multiple interconnected processing systems that exist exclusively on a processing system or can be local or remote to the processing system. Representative embodiments are not limited to the memories mentioned above, and it is understood that other platforms and memories can support the methods described.

[0348] Suitable processors include, by way of example, general-purpose processors, dedicated processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microprocessors, application specific integrated circuits (ASICs), application specific standard products (ASSPs), field programmable gate array (FPGA) circuits, any other type of integrated circuit (IC), and / or state machines.

[0349] Although the present invention has been described with respect to a communication system, it is contemplated that the system can be implemented in software on a microprocessor / general purpose computer (not shown). In certain embodiments, one or more of the functions of the various components can be implemented in software that controls a general purpose computer.

[0350] In addition, although the present invention has been illustrated and described herein with reference to particular embodiments, the present invention is not intended to be limited to the details shown. Rather, various changes may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

1. 1. A method performed by a wireless transmit / receive unit (WTRU), comprising: performing a first listen-before-talk (LBT) procedure before transmitting a physical random access channel (PRACH) preamble, the first listen-before-talk (LBT) procedure being performed according to a listen-before-talk (LBT) configuration, the listen-before-talk (LBT) configuration including a listen-before-talk (LBT) type and a channel access priority class; receiving a random access response including information indicating whether to perform a second listen-before-talk (LBT) procedure before transmitting a transmission scheduled by the random access response; performing a second listen-before-talk (LBT) procedure before transmitting the scheduled transmission, on a condition that the information included in the random access response indicates performing a second listen-before-talk (LBT) procedure; and The method includes:

2. The method of claim 1 , wherein the method includes transmitting the PRACH preamble on a condition that a channel associated with the transmission of the PRACH preamble is determined to be idle according to the first LBT procedure.

3. The method of claim 1, wherein either the first listen-before-talk (LBT) procedure or the second listen-before-talk (LBT) procedure is associated with a slot duration.

4. The method of claim 1, wherein the listen-before-talk (LBT) type includes either (1) a first LBT type associated with a PRACH preamble transmission on resources within a channel occupancy time (COT) and (2) a second LBT type associated with a shared COT.

5. The method of claim 1, wherein the channel access priority class indicates a priority level associated with one or more uplink transmissions from the WTRU.

6. 2. The method of claim 1, further comprising transmitting the scheduled transmission on a condition that a channel associated with the scheduled transmission is determined to be idle according to the second listen-before-talk (LBT) procedure.

7. The method of claim 1, comprising transmitting the scheduled transmission without sensing a channel associated with the scheduled transmission, provided that the information included in the random access response indicates that an LBT procedure is not being performed.

8. A wireless transmit / receive unit (WTRU) comprising circuitry including a processor and a transceiver, The circuit comprises: performing a first listen-before-talk (LBT) procedure before transmitting a physical random access channel (PRACH) preamble, the first listen-before-talk (LBT) procedure being performed according to a listen-before-talk (LBT) configuration, the listen-before-talk (LBT) configuration including a listen-before-talk (LBT) type and a channel access priority class; receiving a random access response including information indicating whether to perform a second listen-before-talk (LBT) procedure before transmitting a transmission scheduled by the random access response; performing a second listen-before-talk (LBT) procedure before transmitting the scheduled transmission, on a condition that the information included in the random access response indicates performing a second listen-before-talk (LBT) procedure; and A WTRU configured to perform the steps of:

9. The WTRU of claim 8 , configured to transmit the PRACH preamble on a condition that a channel associated with the transmission of the PRACH preamble is determined to be idle according to the first LBT procedure.

10. The WTRU of claim 8, wherein either the first listen-before-talk (LBT) procedure or the second listen-before-talk (LBT) procedure is associated with a slot duration.

11. The WTRU of claim 8, wherein the listen-before-talk (LBT) type includes either (1) a first LBT type associated with a PRACH preamble transmission on resources within a channel occupancy time (COT) and (2) a second LBT type associated with a shared COT.

12. The WTRU of claim 8, wherein the channel access priority class indicates a priority level associated with one or more uplink transmissions from the WTRU.

13. 10. The WTRU of claim 8, configured to transmit the scheduled transmission on a condition that a channel associated with the scheduled transmission is determined to be idle according to the second listen-before-talk (LBT) procedure.

14. The WTRU of claim 8, configured to transmit the scheduled transmission without sensing a channel associated with the scheduled transmission, provided that the information included in the random access response indicates that an LBT procedure is not being performed.

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