Method of contention window size adjustment in unlicensed spectrum

Abstract

Methods and apparatus of communication on an unlicensed band are provided.SOLUTION: The method may include transmitting a transport block in each slot of a plurality of slots, and determining a hybrid automatic repeat request (HARQ) status for each of the transmitted transport blocks. The method may further include determining a weighting factor for each of the determined HARQ statuses, and calculating a weighted average of the HARQ statuses for the transmitted transport blocks based on the determined HARQ statuses and the weighting factors. The method may further include adjusting a listen before talk (LBT) contention window size based on the weighted average of the calculated HARQ statuses.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 805,126, filed February 13, 2019, and U.S. Provisional Patent Application No. 62 / 908,220, filed September 30, 2019, the contents of which are incorporated herein by reference. [Background technology]

[0002] Channel access in unlicensed frequency bands typically uses a listen-before-talk (LBT) mechanism or procedure. In an LBT procedure, a network node or WTRU can first detect transmissions taking place on a given channel before commencing its own transmission. In some cases, the LBT procedure is ordered regardless of whether the channel is occupied or not. In other cases, transmissions may be performed immediately after a short switching gap.

[0003] For frame-based systems, the LBT mechanism or procedure may be characterized by a clear channel assessment (CCA) time period (e.g., ~20 μs), a channel occupancy time period (e.g., minimum 1 ms, maximum 10 ms), an idle period (e.g., minimum 5% of channel occupancy time), a fixed frame period (e.g., equal to the channel occupancy time plus the idle period), a short control signaling transmission time (e.g., maximum duty cycle of 5% within a 50 ms observation period), and a CCA energy detection threshold.

[0004] For example, in a load-based system where the transmitting / receiving vehicle may not be fixed in time, the LBT procedure may be characterized by a number N corresponding to the number of clear idle slots in the extended CCA period instead of a fixed frame period. N may be randomly selected within a range. In the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard for operation in unlicensed spectrum, there are two categories of CCA periods for both uplink and downlink transmissions. In the first category, a node may sense the channel for N slot time lengths, where N may be a random value selected from a range of permitted values, called the contention window (CW). The LBT contention window size (CWS) and adjustment may depend on the channel access priority. In the second category, a node may sense the channel for a preconfigured number of slots.

[0005] In communications between a WTRU and a network node, other nodes (e.g., WiFi transmitters) may also be communicating with the network node using unlicensed spectrum, causing interference when the WTRU is close to the network node while the other nodes are not within the WTRU's detection range. Such interference, commonly known as the "hidden node problem," may backfire on the LBT procedure when one WTRU may not be able to detect transmissions by the other. To mitigate the hidden node problem, prior to each transmission, the contention window may be adjusted while considering the status of the last transmission. For example, the status of the last transmission may be indicated to the network via a received acknowledgement (ACK) or negative acknowledgement (NACK) for a downlink transmission, or in the case of an uplink transmission, a new data indicator (NDI) may be toggled. The ACK or NACK may be broadly referred to as HARQ-ACK feedback. In one exemplary implementation of the LBT procedure for downlink transmission, if at least 80% of the HARQ-ACK values ​​of the PDSCH transmissions in the reference subframe are NACKed, the CWS may be increased; otherwise, it remains unchanged. For uplink transmissions, the WTRU may increase the CWS based on whether the NDI has been toggled for the reference HARQ ID, which may correspond to the grant transmitted in the reference subframe. Summary of the Invention

[0006] Provided herein are methods and apparatus for communication over an unlicensed band. The method may include transmitting a transport block in each slot of a plurality of slots and determining a hybrid automatic repeat request (HARQ) status for each of the transmitted transport blocks. The method may further include determining a weighting factor for each of the determined HARQ statuses and calculating a weighted average of the HARQ statuses for the transmitted transport blocks based on the determined HARQ statuses and the weighting factor. The method may further include adjusting a listen-before-talk (LBT) contention window size based on the calculated weighted average of the HARQ statuses. [Brief explanation of the drawings]

[0007] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate similar elements and in which: [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communication system illustrated in FIG. 1A, according to an embodiment. [Figure 1C] 1B is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to an embodiment. [Figure 1D] 1B is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communication system illustrated in FIG. 1A, according to an embodiment. [Figure 2] FIG. 10 is a diagram illustrating the timing of scheduled HARQ feedback in relation to the corresponding PDSCH transmission. [Figure 3]FIG. 10 illustrates scheduling of HARQ-ACK feedback at various timings as may be implemented in NR. [Figure 4] 10 shows an example of a grouping and coordination procedure when performed by a WTRU. [Figure 5] 1 illustrates an example scenario in which a WTRU is configured to group HARQ-ACK statuses corresponding to a series of PUSCH transmissions. [Figure 6] 10 is a flow diagram illustrating an example process by which a WTRU adjusts a CWS using a threshold value. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, the WTRUs 102a, 102b, 102c, 102d, all of which may be referred to as stations (STAs), may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, notebooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, 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 the context of industrial and / or automated processing chains), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The WTRUs 102a, 102b, 102c, and 102d may all be referred to interchangeably as UEs.

[0010] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, the Internet 110, and / or other networks 112. For example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNodeB (eNB), a Home Node B, a Home eNodeB, a Next Generation Node B (e.g., gNode B (gNB)), a New Radio (NR) Node B, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each depicted as a single element, it will be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

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

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

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

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

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

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

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

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

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

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

[0021] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may employ a cellular-based wireless technology, and with a base station 114b, which may employ an IEEE 802.2 wireless technology.

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

[0023] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, other types of integrated circuits (ICs), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated in an electronic package or chip.

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

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

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

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

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

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

[0030] The processor 118 may also be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a 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, an activity tracker, etc. The peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a Hall-effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, etc.

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

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

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

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

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

[0036] The MME 162 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface and may act as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies such as GSM and / or WCDMA.

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

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

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

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

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

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

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

[0044] High-throughput (HT) STAs may use 40 MHz wide channels for communication, for example, by combining a primary 20 MHz channel with adjacent or non-adjacent 20 MHz channels to form the 40 MHz wide channel.

[0045] A very high throughput (VHT) STA can support channels of 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz width. A 40 MHz and / or 80 MHz channel can be formed by combining contiguous 20 MHz channels. A 160 MHz channel can be formed by combining eight contiguous 20 MHz channels or two non-contiguous 80 MHz channels, sometimes referred to as an 80+80 configuration. In the 80+80 configuration, data can be passed through a segment parser after channel encoding, which can split the data into two streams. Inverse fast Fourier transform (IFFT) processing and time-domain processing can be performed separately on each stream. The streams can be mapped onto two 80 MHz channels, and the data can be transmitted by the transmitting STA. In the receiver of the receiving STA, the above operations for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

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

[0047] A WLAN system may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, and the WLAN system includes a channel that may be designated as a primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by the STA that supports the smallest bandwidth operating mode among all STAs operating in the BSS. In an 802.11ah example, the primary channel may be 1 MHz wide for a STA (e.g., an MTC-type device) that supports (e.g., only supports) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) setting may depend on the status of the primary channel. If the primary channel is busy, for example because a STA (which only supports 1 MHz mode of operation) is transmitting to the AP, then all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

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

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

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

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

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

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

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

[0055] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, supporting network slicing (e.g., handling different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, managing registration areas, terminating non-access stratum (NAS) signaling, mobility management, etc. Network slicing may be used by the AMF 182a, 182b to customize CN support for the WTRUs 102a, 102b, 102c based on the type of service being utilized by the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on Ultra-Reliable Low-Latency (URLLC) access, services relying on eMBB access, services for MTC access, etc. The AMFs 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies (e.g., WiFi).

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

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

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

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

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

[0061] One or more emulation devices may perform one or more functions, including all functions, without being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a test scenario in a test lab and / or in a test scenario in a non-deployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may, for example, include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0062] 3GPP is releasing standards for New Radio (NR) technology. Unlike LTE, NR can support variable transmission duration / start symbol and variable HARQ feedback timing. In variable transmission duration, a physical downlink shared channel (PDSCH) or physical uplink shared channel (PUSCH) transmission can occupy a consecutive set of symbols within a slot. When variable feedback timing is implemented, the downlink control information (DCI) containing the DL allocation can include an indication of the HARQ feedback timing for the WTRU. For example, the indication can identify a semi-statically configured time period during which to transmit HARQ feedback. Furthermore, NR can support the use of a dynamic HARQ-ACK codebook, where the size of the codebook depends on the number of scheduled transport blocks (TBs). A next-generation Node B (gNB) can indicate the number of previously scheduled TBs using a counter downlink allocation index (DAI) and / or a total DAI in the DCI. In one embodiment, the counter DAI indicator and the total DAI indicator may each or collectively have a size of 2 bits, which may allow the WTRU to retrieve up to four missing TBs. In other embodiments, the counter DAI indicator and the total DAI indicator may each or collectively have a greater or lesser number of bits, which may allow the WTRU to retrieve a greater or lesser number of bits.

[0063] 3GPP has initiated a work item to support NR operation in unlicensed spectrum. One objective of the work item may be to specify NR-based operation in unlicensed spectrum, including initial access, scheduling / HARQ, and mobility, along with coexistence methods for operation alongside LTE-LAA and other currently operating radio access technologies (RATs). Deployment scenarios may include different standalone NR-based operations. For example, variants of dual connectivity operation may be implemented, such as E-UTRAN New Radio Dual Connectivity (EN-DC) with at least one carrier operating according to the LTE RAT, or NR DC with at least two sets of one or more carriers operating according to the NR RAT. Variants of carrier aggregation (CA), possibly including different combinations of zero or more carriers for each of the LTE and NR RATs, may also be implemented.

[0064] During the study item phase, for example, it was agreed to support four categories of channel access schemes for NR-U operation. Category 1 channel access can involve immediate transmission after a short switching gap. Category 2 channel access can involve LBT operation without random backoff, while categories 3 and 4 can include LBT operation with random backoff and a fixed contention window size (CWS) and Listen-Before-Talk (LBT) operation with random backoff and a variable contention window size, respectively.

[0065] NR-U may also support the possibility to temporarily disable the transmission of HARQ-ACK feedback for a given PDSCH transmission, as well as the possibility to request HARQ-ACK feedback later using DCI without scheduling a transport block (TB).

[0066] In LTE-based operation in an unlicensed spectrum, an evolved Node B (eNB) can rely on the indicated status of one or more PDSCH transmissions to adjust the CWS. Prior to a transmission on the PDSCH, the eNB can maintain a CWS associated with a channel access priority class p. The CWS can be increased or decreased by determining a HARQ-ACK value corresponding to one or more PDSCH transmissions in a reference subframe. The reference subframe may be the starting subframe of the most recent transmission performed on the carrier by the eNB and in which HARQ-ACK is expected to be available. In LTE, HARQ-ACK feedback is transmitted over licensed spectrum and is not dependent on the success or failure of CCA. For uplink transmissions, the WTRU can adjust the CWS based on the new data indicator (NDI) of a recent uplink transmission. One problem caused by the additional procedures in NR is that HARQ-ACK feedback in NR-U may be transmitted over unlicensed spectrum. Therefore, the availability of the HARQ-ACK status of the last transmission at the gNB may not be guaranteed.

[0067] FIG. 2 illustrates the timing of scheduled HARQ feedback relative to a corresponding PDSCH transmission. As shown, a gNB may transmit a transport block on a PDSCH 210 in slot n-4 and schedule a WTRU transmission of HARQ-ACK feedback in slot n. Due to an LBT failure, the HARQ-ACK status for that PDSCH may not be available in slot n-4 as expected. At the gNB, it may not be clear whether the PDSCH transmission was not received by the WTRU or whether the HARQ-ACK transmission failed due to the WTRU's LBT mechanism. For example, it may not be clear whether a hidden node problem occurred or a collision occurred during transmission on the PDSCH. In yet another example, the PUCCH resource indicated by the PDSCH-to-HARQ parameters may fall outside the channel occupation time (COT). In the latter case, similar to an LBT failure, the HARQ-ACK status for the corresponding PDSCH will not be available until at least a new COT is established.

[0068] Another issue can be the support of flexible HARQ timing, e.g., dynamic indication of PDSCH-to-HARQ can result in multiple PDSCH transmissions occurring in the same slot and signaling of HARQ-ACK feedback in different slots, where different HARQ-ACK feedback arriving in different slots can experience different channel conditions.

[0069] FIG. 3 illustrates scheduling of HARQ-ACK feedback at various timings as may be implemented in NR. For example, for three separate PDSCH transmissions 310, 320, and 330 transmitted in slot n-4, the HARQ-ACK feedback for each arrives in slots n-3, n-2, and n-1, respectively, as shown. The transmissions for the three HARQ feedbacks may experience different channel conditions and may be contingent on the failure or success of LBT. Furthermore, as shown in FIG. 3, the PDSCH transmission durations within slot n-4 may vary. Shorter transmissions may experience different channel conditions than longer transmissions. Also, as shown, the start and / or end times of PDSCH transmissions in a given slot may also vary.

[0070] Methods and apparatuses for coordinating CWS are described herein. These solutions can consider, for example, the uncertainty of the HARQ-ACK status of previous transmissions at the transmitter side, as well as variable time lengths and timings of transmissions. As used herein, the term "transmitting node" can refer to a WTRU, a gNB, or any transmitter for wireless communication. Such devices may be configured to operate, for example, in the NR unlicensed spectrum.

[0071] Embodiments directed to CW adjustment are broadly disclosed herein. In one set of solutions, a transmitting node may be configured with a set of values ​​from which the CW may be changed. For example, a transmitting node may be configured with a set of values ​​S={W1, W2, ..., W N The contention window adjustment procedure can be configured in one or multiple steps (e.g., from W1 to W2 or from W1 to W3, where k<=N). k ), increasing the window size, either by one step or multiple steps (e.g., from W2 to W1, or W kThe method may include reducing the size (from W1 to W2) and / or resetting the window size to a default value. In one example solution, the default value may be the smallest value of the set, or the default value may be pre-configured or fixed in the specification, or may be dynamically determined. The transmitting node may determine the adjustment step and / or initial value of the contention window based on one or a combination of factors described below. For example, the transmitting node may determine the initial value and / or adjustment step based on the COT length initiated by another transmitting node. The WTRU may determine the initial value of the CWS based on the COT length when initiated by the gNB.

[0072] In some embodiments, the adjustment step and / or initial value of the CW may depend on the channel access priority, for example, the WTRU may determine the step and initial value based on the channel access priority signaled from the network.

[0073] In some embodiments, the adjustment step and / or initial value of the contention window may depend on the signal and / or channel being transmitted. For example, when the WTRU transmits a scheduling request or HARQ-ACK feedback, the WTRU may select the smallest value from a set of allowed values.

[0074] In some embodiments, the adjustment step and / or initial value of the contention window may depend on the number of contention window adjustments previously performed by the transmitting node.

[0075] In some solutions, a transmitting node may be configured to adjust the contention window corresponding to a given channel access priority (CAP) based solely on previous transmissions performed with that channel access priority. For example, a transmitting node may be configured to perform multiple channel accesses at different priority classes. The transmitting node can adjust the CWS by determining the status of previous transmissions performed using that channel access priority.

[0076] In another solution, a transmitting node may be configured to adjust a CWS corresponding to a given channel access priority based on previous transmissions performed with channel access priorities within a subset of classes for the same channel access category. For example, a transmitting node may be configured to use channel access categories with four different priority classes p1, p2, p3, and p4. Based on the channel access priority mapping shown in Table 1, which represents an example mapping between transmissions of a single CAP and other CAPs, the transmitting node can adjust a CWS for a CAP.

[0077] [Table 1]

[0078] In this example, to adjust the CW size for a transmission with channel access priority p1, the node may consider only the state of previous transmissions with channel access priority p1. For priority p4, the node may consider all transmissions with different channel access priorities p1, p2, p3, and p4 to adjust the contention window. Such mapping can be configured semi-statically using higher layer signaling, or dynamically indicated by the receiving node, for example, using DCI (in the case where the transmitting node is a WTRU and the receiving node is a gNB) or sequence-based signaling.

[0079] In another solution, the transmitting node may group transmission statuses based on the service type of the transmission and adjust the CWS for each type of service. For example, when performing CW adjustment for transmitting URLLC packets, the transmitting node may only consider the HARQ-ACK status of URLLC type services.

[0080] In some solutions, a transmitting node may be configured to adjust the CW for a given channel access category based only on previous transmissions performed using that channel access category. For example, a transmitting node may be configured to use a single channel access category. The transmitting node may adjust the CW by determining the status of previous transmissions performed using that channel access category. In another solution, a transmitting node may be configured to adjust the CW for a given channel access category based on previous transmissions performed using a subset of the channel access categories. The transmitting node may be configured with a mapping between a single channel access category and a set of channel access categories to be considered semi-statically, e.g., using RRC signaling, or dynamically, e.g., using DCI or sequence-based signaling.

[0081] In some solutions, the transmitting node can adjust the CWS based on one parameter or a combination of parameters. For example, one parameter used to adjust the CWS may be the HARQ-ACK status of one or more PDSCH or PUSCH transmissions received in a reference subframe or set of reference subframes. Another parameter may be the HARQ-ACK status of a PDSCH or PUSCH transmission performed in the reference subframe.

[0082] The transmitting node can adjust the CWS based on one or more measurement reports or measurement results. The measurement reports or results can include a channel quality indicator (CQI) range, channel state information (CSI), an SRS transmission, an SINR estimate over a set of slots preceding a transmission, detected energy over a set of slots preceding a transmission, a radio link quality measurement (e.g., radio link monitoring (RLM)), a received power measurement for Layer 1 reference signal received power (L1-RSRP), received CSI reference signal power (CSI-RSRP), received CSI reference signal quality (CSI-RSRQ), beam-related measurements, numerology (e.g., subcarrier spacing), received signal strength indicator (RSSI), or channel occupancy (CO). CO can be determined for each LBT subband as a function of channel load, for example.

[0083] The transmitting node can adjust the CW based on the number N of slot time lengths detected during the previous CW adjustment. The adjustment may be made based on the number of slots in which the channel was determined to be clear, e.g., the number of slots in which the detected energy was below a certain threshold. The adjustment may also be made based on the number of slots in which the channel was determined to be busy, e.g., the number of slots in which the detected energy was above a certain threshold. The adjustment may be based on the total number of slots that are clear and / or the number of times an LBT procedure was postponed. The adjustment may also be based on the total time for one or more previous LBT procedures and / or the average amount of time for a set of previous LBT procedures.

[0084] In some solutions, the transmitting node may be configured to perform a CW adjustment process for each subband within the active bandwidth portion (BWP). For example, the transmitting node may operate on a wide bandwidth portion (WBWP) having multiple subbands and perform an LBT procedure for each subband. The node may perform a channel access procedure for each frequency size equal to 20 MHz. For example, if a transmission fails in a first subband, the CW of a second subband may not be increased. In a first set of solutions, the transmitting node may adjust the CW process independently of other CW adjustment processes. In another set of solutions, the transmitting node may adjust the CW process while considering the status of other CW processes. For example, if the frequency offset between two subbands is lower than a threshold, the transmitting node may consider the CW process status of an adjacent subband.

[0085] In some solutions, the transmitting node may be configured to maintain a CW adjustment process for each BWP, assuming multiple BWPs are configured within the carrier. In such cases, the transmitting node may adjust one CW adjustment process independently of other CW adjustment processes corresponding to different BWPs.

[0086] In some solutions, the transmitting node can obtain a set of LBT subbands for transmission, which may reside within the BWP. The transmitting node can use wideband LBT that covers all LBT subbands and can use a CWS process that is applicable to all LBT subbands. In another approach, a wideband CWS value may be determined as a function of all CWS values ​​for each independent LBT subband. In another approach, the transmitting node can perform multiple LBT procedures (e.g., one procedure per LBT subband) and use an independent CW adjustment process for each independent LBT subband. In yet another approach, the transmitting node can perform multiple LBT procedures, possibly using a single CWS value determined as a function of all CWS values ​​for each independent LBT subband.

[0087] When the WTRU uses a CWS value that is a function of a set of CWS values ​​determined from a set of LBT subbands, the function may be constructed from at least one of several factors. For example, the CWS value used may be the largest or smallest CWS value of all LBT subbands under consideration. The CWS value used may be an average CWS value determined from the CWS values ​​of all LBT subbands under consideration. The CWS value used may be the CWS value of the LBT subband with the highest or lowest index. The CWS value used may be a CWS value of the LBT subband that may be configurable or indicated by the network. The CWS value used may be a CWS value that is configurable or indicated by the network for the set of LBT subbands. The CWS value used may be the most recently used CWS for any LBT subband within the BWP, or the CWS value used may be an adjustment value (e.g., an incremental increase or decrease from a previously used value).

[0088] The CWS used for a set of LBT subbands may be stored within one or all of the CWS processes corresponding to each LBT subband, or may be reserved for use in one or all of the CWS processes. Any such stored CWS may be used in a subsequent LBT procedure. Alternatively, the CWS used for a set of LBT subbands may be stored in the CWS process that will be used for any future use of that particular set of LBT subbands.

[0089] In some solutions, the transmitting node can adjust the CWS based on assistance information received from the receiving node. For example, the WTRU can adjust its CWS based on information received from the gNB. Such information can be explicitly signaled, for example, via a field in the DCI, or implicitly derived from other received signals, such as RRC configuration parameters. For example, in the case where the gNB transmits a sequence-based signal to indicate the start of a shared COT, the sequence used by the gNB can indicate the CWS and / or an initial value to be used by the WTRU when adjusting the CWS. In another example, the sequence used can indicate whether a CWS adjustment is needed or not.

[0090] In yet another embodiment, the WTRU may use information such as a set of PDCCH monitoring opportunities, a control resource set (CORESET), or a search space attribute to determine information for CWS adjustment.

[0091] In some solutions, the transmitting node and the receiving node can cooperate to maintain the same CWS. Such cooperation can be supported by explicitly or implicitly exchanging CWS information. For example, the WTRU can receive the CWS to be used for uplink transmission in the scheduling DCI. In another example, the WTRU can implicitly determine the CWS used by the receiving node.

[0092] In some solutions, the transmitting node may need to take into account numerology, such as subcarrier spacing, slot time length, CP length, etc., to adjust the CW. In one example, the WTRU may detect a DCI that switches the DL BWP. If the active DL BWP and the initial DL BWP have different subcarrier spacings (SCSs) and different CP lengths, the WTRU may need to consider the numerology of the initial BWP for CW adjustment in the active BWP. In one example, if the previous CW size adjustment was based on detecting N slot time lengths with 15 KHz subcarrier spacing in the initial BWP, considering that the slot time length in the active BWP is half that of the initial BWP, the WTRU may need to consider detecting 2N slot time lengths with 30 KHz subcarrier spacing in the active BWP.

[0093] The solutions proposed in the above sections can be applied alone or in combination with the contention window adjustment solutions proposed below for uplink and downlink transmissions.

[0094] Embodiments directed to contention window adjustment for uplink transmissions are described herein. The uplink transmission may include any transmission generated by the WTRU. By way of example and not limitation, it may include a transmission using PUCCH, PUSCH, PRACH, or SRS. The following proposed solutions may be applied alone or in combination. For uplink transmissions, the WTRU may be configured to determine the HARQ-ACK status of a previous transmission based on explicit HARQ-ACK feedback from the gNB or based on NDI toggling of those HARQ IDs used in the uplink grant of the subsequent transmission.

[0095] In a first set of solutions, the WTRU may be configured to consider the HARQ-ACK status of PUSCH transmissions within a configured time window or set of slots prior to the CW adjustment procedure. The time window size may be associated with a certain channel access category or channel access priority. The WTRU may be configured to group HARQ-ACK statuses corresponding to multiple transmissions, average the HARQ-ACK values ​​within the group, and determine a weighted average over the group. The WTRU may apply a weighting factor to each of the HARQ-ACK values ​​for an individual slot or set of slots. The WTRU may be configured to group the HARQ-ACK status of uplink transmissions as described herein, or may do so autonomously based on one or more of several factors.

[0096] FIG. 4 illustrates an example of the grouping and coordination procedure as performed by a WTRU. As shown, the WTRU may determine to group HARQ-ACK statuses based on the time length of the PUSCH transmissions and / or the position of the PUSCH transmissions within a window prior to the CW coordination procedure. As shown in FIG. 4, the WTRU may be configured to transmit a series of transmissions on the PUSCH in a set of reference slots n through n+4. A first transmission 410 may be transmitted by the WTRU in slot n, a second transmission 420 may be transmitted by the WTRU in slot n+2, and a third transmission 430 may be transmitted by the WTRU in slot n+4. The PUSCH transmissions 410, 420, and 430 may have different time lengths and / or different start times, as shown. A HARQ-ACK status may be received at the WTRU from a network node, as shown at 440, 450, and 460. The WTRU may group the information and average the values ​​of the HARQ-ACK status corresponding to the HARQ-ACK feedback 440, 450, and 460 for the PUSCH transmissions 410, 420, and 430. In some embodiments, the WTRU may apply weighting factors to any or all of the determined HARQ-ACK statuses shown in FIG. 4 as C1, C2, and C3.

[0097] Described herein are factors based on which a WTRU may determine to group HARQ-ACK statuses. In some embodiments, for example, a WTRU may determine to group HARQ-ACK statuses based on whether a grant-based PUSCH transmission occurred or whether a configured grant was transmitted.

[0098] In some embodiments, the WTRU may determine to group the HARQ-ACK status based on a channel access category or priority, or the WTRU may determine to group the HARQ-ACK status based on an LBT category or priority used by the gNB to schedule the grant. The WTRU may determine to group the HARQ-ACK status based on a CORESET or search space over which the DCI scheduling the transmission is received. The WTRU may determine to group the HARQ-ACK status based on a monitoring periodicity of a search space over which the DCI scheduling the transmission is received. In some embodiments, the WTRU may determine to group the HARQ-ACK status based on a transmission configuration indicator (TCI) state over which the DCI scheduling the transmission is received. The WTRU may determine to group the HARQ-ACK status based on a bandwidth portion over which the DCI scheduling the transmission is received.

[0099] The WTRU may determine to group the HARQ-ACK status transmitted by the gNB based on some a priori knowledge, such as discontinuous transmission (DTX) at the gNB due to an LBT procedure failure at the WTRU, DTX at the gNB due to a false detection of the PUSCH, PUSCH transmission attributes such as MCS, redundancy version (RV) or number of repetitions, or knowledge of HARQ process information such as HARQ ID.

[0100] In some solutions, the WTRU may receive configuration information from the network with a weighted average coefficient for each group. For example, the WTRU may receive an RRC configuration associating a coefficient with each group. In another solution, the DCI scheduling the transmission may indicate the coefficient for that group of transmissions. In another solution, the WTRU may autonomously determine the coefficient for the weighted average based on, for example, the type of traffic scheduled within the group. The WTRU may apply a weighting coefficient across a group of HARQ-ACK values, or, as described above, the WTRU may apply a weighting coefficient to each of the HARQ-ACK values ​​for an individual slot or set of slots.

[0101] 5 illustrates an example scenario in which a WTRU is configured to group HARQ-ACK statuses corresponding to a series of PUSCH transmissions. As shown, the WTRU may transmit a series of transmissions on the PUSCH in a set of reference slots n through n+6. A first transmission 510 may be transmitted by the WTRU in slot n, a second transmission 520 may be transmitted by the WTRU in slot n+2, a third transmission 530 may be transmitted by the WTRU in slot n+4, and a fourth transmission 540 may be transmitted by the WTRU in slot n+6. The PUSCH transmissions 510, 520, 530, and 540 may have different time lengths and / or different start times. In subsequent slots, the WTRU may receive HARQ feedback or determine HARQ-ACK statuses 551, 552, 561, and 562 corresponding to each of the PUSCH transmissions 510, 520, 530, and 540. HARQ-ACK status 551, 552, 561, and 562 may comprise a single bit value of 0 or 1 and may be received by the WTRU from a network node. Alternatively, the HARQ-ACK status may be implicitly determined based on the toggling of the NDI field in the DCI. The WTRU may group the HARQ-ACK feedback into groups 550 and 560, for example, according to one or more of the factors described in the paragraph above, and the WTRU may average the value of the HARQ-ACK status for each of the groups. In the embodiment as shown, the WTRU may also apply a weighting factor to each of the groups of HARQ-ACK status, indicated by C1 and C2.

[0102] In some solutions, the WTRU may be configured to adjust the CWS while considering the HARQ-ACK status per CBG. In a first set of solutions, the WTRU may be configured to consider the HARQ-ACK status per TB and the HARQ-ACK status per CBG differently. For example, the WTRU may perform a weighted average over all HARQ-ACK statuses, with a lower weight assigned to the HARQ-ACK status per CBG. In other solutions, the WTRU may be configured to assign the same weight to both the HARQ-ACK status per TB and per CBG, for example, when the gNB maps the CBG to the entire subband. Upon receiving an uplink grant and determining that the CBG is mapped to the entire subband, the HARQ-ACK status per CBG can provide the WTRU with the channel conditions of the entire subband. The WTRU may be configured to determine the HARQ-ACK status of the CBG using the CBG transmission indication and / or CBG flushing indication received in the DCI scheduling the UL grant.

[0103] In some solutions, the WTRU may adjust the contention window size based on a channel quality indicator (CQI) determination prior to performing the CW adjustment procedure at a reference slot, within a set of slots, or within a configured time window. For example, the WTRU may be configured to calculate an average value of the CQI determined over K slots prior to the CW adjustment. In some embodiments, the WTRU may be configured to calculate a weighted average of the CQI. For example, the WTRU may be configured to apply a higher factor to the last determined CQI than to the previous CQI. Furthermore, the WTRU may be configured with a set of CQI average thresholds, each corresponding to a step in the contention window adjustment process. For example, the WTRU may calculate a weighted average of the CQIs over {T1, T2, ..., T N} threshold can be configured. The calculated mean is T i and T i+1 If the CWS is between T and T, the CWS may be increased by one step and the calculated average i+1 and T i+2 If it is between , the CWS may be increased by two steps.

[0104] In a solution, the WTRU may be configured with a CWS based on measurements received on a configured reference signal or another signal, which may be in the form of path loss, estimated SINR, or another metric related to signal quality or signal strength.

[0105] The WTRU may be configured with one or more thresholds and one or more CWS values ​​by which to determine the applicable CWS, which may be made based on WTRU measurements or may be directed by the gNB.

[0106] FIG. 6 is a flow diagram illustrating an example process by which a WTRU adjusts a CWS using threshold values. As shown, at 610, the WTRU may be configured with an initial CW size and one or more threshold values. The initial CW size and / or threshold values ​​may be configured via semi-static signaling or may be dynamically determined. At 620, the WTRU may calculate an average or weighted average of multiple HARQ statuses, for example, according to the methods described above. If the average or weighted average of the HARQ statuses is lower than a threshold, the WTRU may determine to maintain the CW at the initial CWS. If the calculated average is equal to or exceeds a threshold value, the WTRU may determine to increase the CWS by applying CWS adjustment steps, as shown at 630. For example, as broadly described in the paragraph above with respect to CW adjustment, the WTRU may determine a set of adjustment steps S={W1, W2, ..., W N}. In some embodiments, for example, the WTRU may apply successive adjustment steps W1 or W2 depending on the number of previously performed adjustments. In another embodiment, the WTRU may apply successive adjustment steps depending on whether the calculated average or weighted average exceeds a further threshold value beyond the first one.

[0107] In the solution, the WTRU may be configured to determine the CWS based on downlink measurements, such as path loss calculations, RSSI, radio resource management (RRM) parameters, or CO values, any of which may be used to estimate the uplink SINR. In some embodiments, the WTRU may be configured with two threshold values ​​T1 and T2 along with three CWS values. Thus, based on the CQI estimation, the WTRU can select one of three pre-configured CWS values ​​by comparing the estimated CQI with the configured thresholds.

[0108] In an alternative solution, the WTRU may be configured to determine the CWS based on another configured parameter, such as the MCS for the scheduled uplink transmission. In one case, the WTRU may be configured with, for example, two threshold values ​​T1 and T2 along with three CWS values. Based on the configured MCS for the upcoming or immediate scheduled uplink transmission, the WTRU may select one of the three pre-configured CWS values, for example, by comparing the configured MCS to the configured thresholds.

[0109] In some solutions, the WTRU can adjust the contention window size based on the COT characteristics of the gNB. For example, depending on the COT duration of the gNB, the WTRU can adjust the CWS accordingly. If the COT duration of the gNB is relatively large (e.g., 10 ms), the WTRU may be configured to increase the CWS during the access channel procedure to ensure fairness among nodes using other RATs, such as wireless local area networks (WLANs).

[0110] Embodiments directed to CW adjustment for downlink transmissions are described herein. The downlink transmissions may include any transmissions generated by a gNB. By way of example and not limitation, the downlink transmissions may include transmissions using PDCCH, PDSCH, PBCH, PSS / SSS, DMRS, or CSI-RS. The following proposed solutions may be applied either alone or in combination.

[0111] In some solutions, the gNB can adjust the contention window size of a transmission based on the HARQ-ACK status of a previous transmission performed within a reference slot. In one group of solutions, the gNB can group HARQ-ACK feedback based on the arrival time of each ACK / NACK feedback. For example, HARQ-ACKs arriving at the same time instance, or within the same subslot, or within the same slot, can be associated with the same group. Such feedbacks can be considered to share the same HARQ-ACK timing.

[0112] In one example solution, groups of NACKs with the same HARQ-ACK timing may be averaged. A weighted average can then be calculated from the averages obtained for each HARQ-ACK timing. The weights applied per HARQ timing group can be semi-statically configured or dynamically adapted based on WTRU measurement reports. In one scenario, the gNB can adjust the CWS if the weighted average is above a configured threshold.

[0113] Alternatively, the gNB may be configured with a set of weighted average thresholds, each corresponding to a CW adjustment step. In a corresponding scenario, the gNB may attempt to access the channel in slot n, and the reference slot may have a relative timing of n-3. The gNB may be performing an M1 PDSCH transmission in slot n-3, where it expects feedback in slot n-2. The gNB may also be performing an M2 PDSCH transmission in slot n-3, where it expects feedback in slot n-1. Finally, the gNB may be performing an M3 PDSCH transmission in slot n-3, where it expects feedback in slot n. In this example, the weighted average may be calculated as follows:

[0114]

number

[0115] In another solution, the gNB may group HARQ-ACK feedback based on the time length of the PDSCH transmission and / or based on the position of the PDSCH transmission within the slot. Each HARQ-ACK value associated with a certain starting position and / or time length may be averaged. A weighted average may then be calculated among the averages obtained for each HARQ-ACK group. The weight of each HARQ group may be semi-statically configured or dynamically adapted based on any of the above-mentioned downlink measurements reported by the WTRU.

[0116] In one set of solutions, to adjust the CW, the gNB may consider the status of HARQ-ACK feedback transmitted by WTRUs using certain channel access categories and / or priorities. In one example, the gNB may consider HARQ-ACK status from WTRUs using a channel access category that specifies immediate transmission after a short switching gap. In another example, the gNB may consider HARQ-ACK status from WTRUs that used a channel access category without random backoff. In another example, the gNB may group the HARQ-ACK status based on the channel access category used by the WTRU. A weighted average may be calculated among the groups, with each group having a different weight. For example, a group of HARQ-ACK status from WTRUs that used a channel access category with immediate transmission after a short switching gap may have a higher weight compared to HARQ-ACK feedback from WTRUs that performed channel access without random backoff.

[0117] In other solutions, the gNB may consider HARQ-ACK feedback that is not scheduled but triggered by DCI. For example, these solutions may apply when the gNB schedules transport blocks without providing HARQ-ACK timing and triggers the transmission of HARQ-ACK feedback corresponding to the scheduled transport blocks later, e.g., in a subsequent slot. Such HARQ-ACK feedback may have a higher priority or a higher weighting factor when used to calculate the weighted average.

[0118] In some solutions, the gNB may determine that a NACK is indicated for a given transmission based on one or more conditions. In one exemplary condition, the gNB may simply receive a NACK from the WTRU. In another exemplary condition, no HARQ-ACK feedback is received or DTX is detected for K number of slots and / or symbols. In another event, no HARQ-ACK feedback may be received within the scheduled HARQ-ACK time frame, but one or more uplink transmissions may be received from the WTRU in one or more subsequent slots or symbols. The uplink transmissions may include scheduling requests, PRACH transmissions, PUSCH transmissions of configured grants, and / or grant-based PUSCH transmissions. In another condition, the number of NACKs received per CBG of a transport block may exceed a threshold.

[0119] In some solutions, the gNB can adjust the contention window size while considering the HARQ-ACK status per CBG. In a first set of solutions, the gNB can consider the HARQ-ACK status per TB and the HARQ-ACK status per CBG differently. For example, the gNB can perform a weighted average over all ACK / NACK values, with a lower weight assigned to the HARQ-ACK feedback per CBG. In another set of solutions, the gNB can assign the same weight to both the HARQ-ACK status per TB and per CBG. For example, the gNB can map the CBG to the entire subband. In such a case, the HARQ-ACK status per CBG can indicate the channel conditions of the entire subband.

[0120] In some solutions, the WTRU may be configured with a CWS based on measurements of a configured reference signal or another signal. The measurements may be in the form of SNR, SINR, CO, RSSI, or another metric. In some solutions, the gNB may adjust the CWS prior to the CWS adjustment based on the WTRU's CQI report received in the reference slot or measurements by the WTRU within the reference slot or set of slots. For example, the gNB may calculate the average CQI reported by different WTRUs within the reference slot or set of slots.

[0121] The WTRU may be configured with one or more thresholds and one or more CWS values ​​to determine the applicable CWS. The determination may be based on WTRU measurements or may be directed by the gNB.

[0122] In some solutions, the WTRU may be configured to determine the CWS based on downlink measurements, such as CSI-RS or DMRS, and estimate the downlink CQI or SINR. In one case, the WTRU may be configured with two threshold values ​​T1 and T2 along with three CWS values. Thus, based on its CQI estimation, the WTRU can select one of three pre-configured CWS values ​​by comparing the estimated CQI with the configured thresholds.

[0123] In an alternative solution, the WTRU may be configured to determine the CWS based on another configured parameter, such as the MCS for the scheduled transmission. In a typical case, the WTRU may be configured with two threshold values ​​T1 and T2 along with three CWS values. Based on its configured MCS for a forthcoming or immediate scheduled transmission, the WTRU can select one of the three pre-configured CWS values ​​by comparing the configured MCS to the configured thresholds. In other cases, a larger or smaller number of threshold values ​​and / or a larger or smaller number of CWS values ​​may be implemented.

[0124] The WTRU may be configured to report the presence of a hidden node. The WTRU can possibly determine the presence of a hidden node as a function of interference measurements. In another method, the WTRU can determine the presence of a hidden node based on past attempts by the WTRU and perform an LBT procedure. For example, the WTRU can perform an LBT procedure at configurable time instances and determine, from that perspective, whether the channel is clear. The WTRU can then possibly report such results in a future transmission.

[0125] While features and elements have been described above in separate combinations, those skilled in the art will recognize that each feature or element may be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor associated with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. 1. A wireless transmit / receive unit (WTRU) comprising a processor and a memory, The processor and memory receiving a first hybrid automatic repeat request (HARQ) feedback corresponding to a reference time window; adjusting or resetting a contention window size (CWS) based on a first HARQ feedback corresponding to the reference time window, wherein the WTRU is configured to use a first CWS adjustment rule when the HARQ feedback corresponds to a transport block (TB)-based HARQ feedback, and the WTRU is configured to use a second CWS adjustment rule when the HARQ feedback corresponds to a code block group (CBG)-based HARQ feedback; determining that a channel used to transmit a physical uplink shared channel (PUSCH) transmission is clear based on the adjusted or reset CWS; and transmitting the PUSCH transmission based on a determination that the channel is clear according to the adjusted or reset CWS; The WTRU is configured to perform the following:

2. 2. The WTRU of claim 1, wherein the first CWS adjustment rule is applied to TB-based HARQ feedback, the second CWS adjustment rule is applied to CBG-based HARQ feedback, and the first CWS adjustment rule is applied to criteria for determining whether to adjust or reset the CWS, the criteria being different from the criteria applied when using the second CWS adjustment rule.

3. The processor: determining, based on the adjusted or reset CWS, that a channel used to transmit at least a third PUSCH transmission is clear; and transmitting a third PUSCH transmission based on a determination that the channel is clear according to the adjusted or reset CWS; The WTRU of claim 1 , further configured to:

4. 2. The WTRU of claim 1, wherein the first CWS adjustment rule includes applying a first weighting factor based on whether the HARQ feedback corresponds to the TB-based HARQ feedback and comparing the weighted HARQ feedback to a first threshold, and the second CWS adjustment rule includes applying a second weighting factor based on whether the HARQ feedback corresponds to the CBG-based HARQ feedback and comparing the weighted HARQ feedback to a second threshold.

5. The WTRU of claim 4 , wherein the first weighting factor and the second weighting factor are different.

6. The WTRU of claim 1 , wherein the HARQ feedback corresponds to an ACK for the reference time window.

7. The WTRU of claim 1 , wherein the HARQ feedback corresponds to a respective ACK or a respective NACK for each of the CBGs.

8. The WTRU of claim 1 , wherein the reference time window corresponds to a number of slots.

9. The WTRU of claim 1 , wherein the reference time window corresponds to a channel occupancy time.

10. 1. A method performed by a wireless transmit / receive unit (WTRU), comprising: receiving a first hybrid automatic repeat request (HARQ) feedback corresponding to a reference time window; adjusting or resetting a contention window size (CWS) based on a first HARQ feedback corresponding to the reference time window, wherein the WTRU is configured to use a first CWS adjustment rule when the HARQ feedback corresponds to a transport block (TB)-based HARQ feedback, and the WTRU is configured to use a second CWS adjustment rule when the HARQ feedback corresponds to a code block group (CBG)-based HARQ feedback; determining that a channel used to transmit a physical uplink shared channel (PUSCH) transmission is clear based on the adjusted or reset CWS; and transmitting the PUSCH transmission based on a determination that the channel is clear according to the adjusted or reset CWS; A method comprising:

11. 11. The method of claim 10, wherein the first CWS adjustment rule is applied to TB-based HARQ feedback, the second CWS adjustment rule is applied to CBG-based HARQ feedback, and the first CWS adjustment rule is applied to criteria for determining whether to adjust or reset the CWS, the criteria being different from the criteria applied when using the second CWS adjustment rule.

12. determining, based on the adjusted or reset CWS, that a channel used to transmit at least a third PUSCH transmission is clear; and transmitting a third PUSCH transmission based on a determination that the channel is clear according to the adjusted or reset CWS; 11. The method of claim 10, further comprising:

13. 11. The method of claim 10, wherein the first CWS adjustment rule includes applying a first weighting factor based on whether the HARQ feedback corresponds to the TB-based HARQ feedback and comparing the weighted HARQ feedback to a first threshold, and the second CWS adjustment rule includes applying a second weighting factor based on whether the HARQ feedback corresponds to the CBG-based HARQ feedback and comparing the weighted HARQ feedback to a second threshold.

14. The method of claim 13 , wherein the first weighting factor and the second weighting factor are different.

15. The method of claim 10 , wherein the HARQ feedback corresponds to an ACK for the reference time window.

16. The method of claim 10 , wherein the HARQ feedback corresponds to a respective ACK or a respective NACK for each of the CBGs.

17. The method of claim 10 , wherein the reference time window corresponds to a number of slots.

18. The method of claim 10 , wherein the reference time window corresponds to a channel occupancy time.

Images