Method for receiving CSI-RS and CSI feedback in NR-U

Abstract

A method for use in a wireless transmit / receive unit is disclosed. The method may comprise: obtaining a transmission opportunity of a channel state information reference signal (CSI-RS); obtaining at least one conditional transmission opportunity of the CSI-RS; and determining whether to transmit the CSI-RS in the transmission opportunity, and if the CSI-RS is not transmitted in the transmission opportunity, detecting whether to transmit the CSI-RS in one of the at least one conditional transmission opportunity.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of August 13, 2020, an application number of 202080062579.8, and an invention title of "Method for Receiving CSI-RS and CSI Feedback in NR-U".

[0002] Cross-reference to related patent applications

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 886,159, filed on August 13, 2019, the content of which is incorporated herein by reference. Background of the Invention

[0004] Transmissions in New Radio Unlicensed Spectrum (NR-U) depend on the acquired channels. Thus, signals with fixed periods may not be transmitted at every configured occasion. Examples of such signals include periodic or semi-persistent Channel State Information Reference Signals (CSI-RS). However, there are benefits to configuring periodic or semi-persistent CSI-RS in NR-U. For example, compared to aperiodic CSI-RS, there is reduced signaling overhead. The Maximum Channel Occupancy Time (COT) duration implies any reduction in signaling, and thus reducing channel acquisition is beneficial. Another benefit is that a Wireless Transmit / Receive Unit (WTRU) may even be able to receive CSI-RS outside of the officially defined COT.

[0005] However, the problem that may arise is that the WTRU must determine whether the CSI-RS is actually transmitted at a certain occasion or is discarded because the channel has not been acquired yet. This is necessary because it may affect the measurements that the WTRU may perform and can lead to incorrect assumptions about the channel characteristics. Such incorrect measurements, assumptions, and measurement feedback can lead to incorrect WTRU scheduling, which can greatly affect system throughput. Additionally, incorrect measurements can lead to unnecessary feedback reports, which may also degrade the overall system performance due to unnecessary channel acquisition. Summary of the Invention

[0006] Disclosed is a method used in a wireless transmit / receive unit. The method may include: obtaining a transmission occasion of a Channel State Information Reference Signal (CSI-RS); obtaining at least one conditional transmission occasion of the CSI-RS; and determining whether the CSI-RS is transmitted at the transmission occasion, wherein in the case where the CSI-RS is not transmitted at the transmission occasion, detecting whether the CSI-RS is transmitted at one of the at least one conditional transmission occasions.

[0007] A wireless transmit / receive unit (WTRU) is disclosed. The WTRU may include: a processor configured to obtain a transmission occasion of a channel state information reference signal (CSI-RS); obtain at least one conditional transmission occasion of the CSI-RS; and determine whether to transmit the CSI-RS in the transmission occasion, wherein, in a case where the CSI-RS is not transmitted in the transmission occasion, the processor is further configured to detect whether to transmit the CSI-RS in one of the at least one conditional transmission occasions.

[0008] As discussed, in order to prevent incorrect measurements and incorrect measurement feedback, a method for enabling the WTRU to determine whether there is a CSI-RS is needed. Considering the need to successfully acquire the channel before transmission, a method for increasing the robustness of CSI-RS transmission may also be needed. Considering lost CSI-RS transmissions, the WTRU may also need a method for handling measurements and reporting appropriate values. Additionally, considering the channel acquisition requirements, the feedback resources may also need to increase in robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the drawings, in which like reference numerals indicate like elements and in which:

[0010] Figure 1A is a system diagram showing an exemplary communication system in which one or more of the disclosed embodiments may be implemented;

[0011] Figure 1B is a system diagram showing an exemplary wireless transmit / receive unit (WTRU) that may be used within the Figure 1A shown communication system, according to one embodiment;

[0012] Figure 1C is a system diagram showing an exemplary radio access network (RAN) and an exemplary core network (CN) that may be used within the Figure 1A shown communication system, according to one embodiment;

[0013] Figure 1D is a system diagram showing another exemplary RAN and another exemplary CN that may be used within the Figure 1A shown communication system, according to one embodiment;

[0014] Figure 2 is a diagram showing an indication of the presence of a channel state information reference signal (CSI-RS) resource;

[0015] Figure 3 is a schematic diagram of a WTRU determining whether there is a previous CSI-RS based on the sequence of currently received CSI-RS; and

[0016] Figure 4A is a flowchart showing a method according to an embodiment of the present application; and

[0017] Figure 4B is a diagram of CSI-RS configured every mth time slot. DETAILED DESCRIPTION

[0018] Figure 1A is a schematic diagram showing an exemplary communication system 100 in which one or more of the disclosed embodiments may be implemented. The communication system 100 may be a multi-access system that provides content such as voice, data, video, messages, broadcasts, etc. to a plurality of wireless users. The communication system 100 may enable a plurality of 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-tail unique word discrete Fourier transform spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0019] As Figure 1AAs shown, communication 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, but it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d (any of which may be referred to as a station (STA)) 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 telephones, personal digital assistants (PDAs), smart phones, laptop computers, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearable devices, 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 environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0020] Communication system 100 may also include base station 114a and / or base station 114b. Each of base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks such as CN 106, the Internet 110, and / or other networks 112. By way of example, base stations 114a, 114b may be base transceiver stations (BTSs), NodeBs, evolved NodeBs (eNBs), home NodeBs, home evolved NodeBs, next generation NodeBs, such as gNode B (gNB), New Radio (NR) NodeB, site controllers, access points (APs), wireless routers, etc. Although base stations 114a, 114b are each depicted as a single element, it should be understood that base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0021] Base station 114a may be part of RAN 104, which may 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 may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, and the base station may be referred to as a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. The cell may provide coverage of wireless services to a specific geographical area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, the cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in the desired spatial direction.

[0022] Base stations 114a, 114b may communicate with one or more of WTRUs 102a, 102b, 102c, 102d via air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, millimeter wave, infrared (IR), ultraviolet (UV), visible light, etc.). Any suitable radio access technology (RAT) may be used to establish air interface 116.

[0023] More specifically, as noted above, communication system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, base station 114a in RAN 104 and WTRUs 102a, 102b, 102c may implement radio technologies such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish air interface 116. 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).

[0024] In one embodiment, base station 114a and WTRUs 102a, 102b, 102c may implement radio technologies such as evolved UMTS terrestrial radio access (E-UTRA), which may use Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-A Pro to establish the air interface 116.

[0025] In one embodiment, base station 114a and WTRUs 102a, 102b, 102c may implement radio technologies such as NR radio access, which may use NR to establish the air interface 116.

[0026] In one embodiment, base station 114a and WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, base station 114a and WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together using, for example, the dual connectivity (DC) principle. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions to / from multiple types of base stations (e.g., eNBs and gNBs).

[0027] In other embodiments, base station 114a and WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wi-Fi), IEEE 802.16 (i.e., 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 Rate for GSM Evolution (EDGE), GSM EDGE (GERAN), etc.

[0028] Figure 1AThe base station 114b therein can be, for example, a wireless router, a home Node B, a home evolved Node B, or an access point, and can utilize any suitable RAT to facilitate wireless connections in local areas such as commercial premises, homes, vehicles, campuses, industrial facilities, air corridors (e.g., for drones), roads, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d can 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 can 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 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 Figure 1A shown, 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.

[0029] The RAN 104 can communicate with the CN 106, which can be any type of network configured to provide voice, data, applications, and / or Internet protocol voice technology (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data can have different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 can provide call control, billing services, location-based services, prepaid calls, Internet connections, video distribution, etc., and / or perform advanced security functions, such as user authentication. Although not shown in Figure 1A it, it should be understood that the RAN 104 and / or the CN 106 can communicate directly or indirectly with other RANs using the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104 that can utilize NR radio technology, the CN 106 can also communicate with another RAN (not shown) that uses GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0030] CN 106 can also act as a gateway for WTRU 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the network 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.

[0031] Some or all of the WTRU 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRU 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, Figure 1A the illustrated WTRU 102c may be configured to communicate with a base station 114a that may employ a cellular-based radio technology and with a base station 114b that may employ an IEEE 802 radio technology.

[0032] Figure 1B is a system diagram showing an exemplary WTRU 102. As Figure 1B shown, the WTRU 102 may include a processor 118, a transceiver 120, transmit / receive elements 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripheral devices 138, among others. It should be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with the embodiments.

[0033] The processor 118 may be a general-purpose processor, a dedicated 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), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal encoding, data processing, power control, input / output processing, and / or any other functions that enable 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 elements 122. AlthoughFigure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0034] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) via the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be a transmitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive RF and optical signals. It should be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0035] Although the transmit / receive element 122 is depicted as a single element in Figure 1B the WTRU 102 may include any number of transmit / receive elements 122. More specifically, 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 via the air interface 116.

[0036] The transceiver 120 may be configured to modulate the signals to be transmitted by the transmit / receive element 122 and demodulate the signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs (such as NR and IEEE 802.11).

[0037] The processor 118 of the WTRU 102 may be coupled to the speaker / microphone 124, keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from any type of suitable memory (such as the non-removable memory 130 and / or the removable memory 132) and store data in any type of suitable memory. The non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from a memory that is not physically located on the WTRU 102 (such as on a server or a home computer (not shown)) and store data in that memory.

[0038] The processor 118 may receive power from the power supply 134 and may be configured to distribute and / or control power to other components in the WTRU 102. The power supply 134 may be any suitable device for powering the WTRU 102. For example, the power supply 134 may include one or more dry battery packs (e.g., nickel cadmium (NiCd), nickel zinc (NiZn), nickel metal hydride (NiMH), lithium ion (Li-ion), etc.), a solar cell, a fuel cell, etc.

[0039] 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 the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) via the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It should be understood that the WTRU 102 may obtain location information by any suitable location determination method while remaining consistent with the embodiments.

[0040] The processor 118 may also be coupled to other peripheral devices 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connections. For example, the peripheral devices 138 may include an accelerometer, an electronic 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, Modules, FM radio units, digital music players, media players, video game player modules, Internet browsers, virtual reality and / or augmented reality (VR / AR) devices, activity trackers, etc. Peripheral device 138 may include one or more sensors. The sensors may be one or more of the following: gyroscopes, accelerometers, Hall effect sensors, magnetometers, orientation sensors, proximity sensors, temperature sensors, time sensors; geographical location sensors, altimeters, light sensors, touch sensors, magnetometers, barometers, gesture sensors, biometric sensors, humidity sensors, etc.

[0041] WTRU 102 may include a full-duplex radio, for which the transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and DL (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via signal processing performed by hardware (e.g., chokes) or via a processor (e.g., a separate processor (not shown) or via processor 118). In one embodiment, WTRU 102 may include a half-duplex radio, for which the transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL (e.g., for reception)).

[0042] Figure 1C is a system diagram showing RAN 104 and CN 106 according to one embodiment. As described above, RAN 104 may communicate with WTRU 102a, 102b, 102c via air interface 116 using E-UTRA radio technology. RAN 104 may also communicate with CN 106.

[0043] RAN 104 may include evolved Node Bs 160a, 160b, 160c, but it should be understood that RAN 104 may include any number of evolved Node Bs while remaining consistent with the embodiment. Each of evolved Node Bs 160a, 160b, 160c may include one or more transceivers for communicating with WTRU 102a, 102b, 102c via air interface 116. In one embodiment, evolved Node Bs 160a, 160b, 160c may implement MIMO technology. Thus, evolved Node B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from WTRU 102a.

[0044] Each of evolved Node Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, etc. As Figure 1C shown, evolved Node Bs 160a, 160b, 160c may communicate with each other via the X2 interface.

[0045] Figure 1C The CN 106 shown may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (PGW) 166. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0046] The MME 162 may be connected to each of the evolved Node Bs 162a, 162b, 162c in the RAN 104 via the 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, bearer activation / deactivation, selecting a particular serving gateway during the initial attachment of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide control plane functions for handover between the RAN 104 and other RANs (not shown) employing other radio technologies such as GSM and / or WCDMA.

[0047] The SGW 164 may be connected to each of the evolved Node Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions such as anchoring the user plane during handover between evolved Node Bs, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, etc.

[0048] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to a packet switched network such as the Internet 110 to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0049] CN 106 may facilitate communication with other networks. For example, CN 106 may provide the WTRUs 102a, 102b, 102c with access to a circuit-switched network such as the PSTN 108 to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, CN 106 may include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between CN 106 and the PSTN 108 or may communicate with the IP gateway. Additionally, 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.

[0050] Although the WTRU is described in Figures 1A to 1D as a wireless terminal, it is contemplated that in some representative embodiments, such a terminal may (e.g., temporarily or permanently) use a wired communication interface with a communication network.

[0051] In a representative embodiment, the other network 112 may be a WLAN.

[0052] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a distribution system (DS) or another type of wired / wireless network that carries traffic to and / or from the BSS. Traffic originating outside the BSS and destined for an STA may reach the STA through the AP and may be delivered to the STA. Traffic originating from an STA and destined for a destination outside the BSS may be sent to the AP for delivery to the corresponding destination. Traffic between STAs within the BSS may be sent through the AP, e.g., where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between a source and destination STA (e.g., directly between them) using direct link setup (DLS). In some representative embodiments, DLS may 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 STAs) may communicate directly with each other. The IBSS communication mode may sometimes be referred to in this document as an "ad-hoc" communication mode.

[0053] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may transmit beacons on a fixed channel (such as the primary channel). The primary channel may be of a fixed width (e.g., 20 MHz bandwidth) or dynamically set width. The primary channel may be the operation channel of the BSS and may be used by the STA to establish a connection with the AP. In some representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, the STA (e.g., each STA) (including the AP) may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. Only one STA (e.g., only one station) may transmit at any given time in a given BSS.

[0054] A high throughput (HT) STA may communicate using a 40 MHz wide channel, e.g., by combining the primary 20 MHz channel with an adjacent or non - adjacent 20 MHz channel to form a 40 MHz wide channel.

[0055] An extremely high throughput (VHT) STA may support channels that are 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide. The 40 MHz and / or 80 MHz channels may be formed by combining consecutive 20 MHz channels. The 160 MHz channel may be formed by combining eight consecutive 20 MHz channels, or by combining two non - consecutive 80 MHz channels (which may be referred to as an 80 + 80 configuration). For the 80 + 80 configuration, after channel coding, the data may pass through a segment parser that may divide the data into two streams. The inverse fast Fourier transform (IFFT) processing and time - domain processing may be performed separately on each stream. These streams may be mapped to two 80 MHz channels, and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations for the 80 + 80 configuration described above may be reversed, and the combined data may be sent to the media access control (MAC).

[0056] 802.11af and 802.11ah support operation modes below 1 GHz. Compared to those used in 802.11n and 802.11ac, the channel operation bandwidth and carriers are reduced in 802.11af and 802.11ah. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV white space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, such as limited capabilities, including supporting (e.g., only supporting) certain bandwidths and / or limited bandwidths. MTC devices may include a battery with a battery life higher than a threshold (e.g., to maintain a very long battery life).

[0057] A WLAN system that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah includes a channel that can be designated as the primary channel. The primary channel may have a bandwidth equal to the maximum common operation bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or restricted by the STA (which supports the minimum bandwidth operation mode) from all STAs operating in the BSS. In an example of 802.11ah, for an STA (e.g., an MTC type device) that supports (e.g., only supports) the 1 MHz mode, the primary channel may be 1 MHz wide, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operation modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because an STA (only supporting the 1 MHz operation mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0058] In the United States, the available frequency band for 802.11ah is 902 MHz to 928 MHz. In Korea, the available frequency band is 917.5 MHz to 923.5 MHz. In Japan, the available frequency band is 916.5 MHz to 927.5 MHz. The total available bandwidth for 802.11ah is 6 MHz to 26 MHz, depending on the country code.

[0059] Figure 1D is a system diagram showing RAN 104 and CN 106 according to one embodiment. As noted above, RAN104 may employ NR radio technology to communicate with WTRU 102a, 102b, 102c via the air interface 116. RAN 104 may also communicate with CN106.

[0060] RAN 104 may include gNBs 180a, 180b, 180c, but it should be understood that RAN 104 may include any number of gNBs while remaining consistent with the embodiments. Each of gNBs 180a, 180b, 180c may include one or more transceivers to communicate with WTRUs 102a, 102b, 102c via air interface 116. In one embodiment, gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from gNBs 180a, 180b, 180c. Thus, gNB 180a, for example, may use multiple antennas to transmit wireless signals to WTRU 102a and / or receive wireless signals from WTRU 102a. In one embodiment, gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, gNB 180a may transmit multiple component carriers to WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum, while the remaining component carriers may be on licensed spectrum. In one embodiment, gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) technology. For example, WTRU 102a may receive a coordinated transmission from gNB 180a and gNB 180b (and / or gNB 180c).

[0061] WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, the OFDM symbol interval and / or the OFDM subcarrier interval may vary for different transmissions, different cells, and / or different portions of the radio transmission spectrum. WTRUs 102a, 102b, 102c may use subframes or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing different numbers of OFDM symbols and / or having an absolute time length that continuously varies) to communicate with gNBs 180a, 180b, 180c.

[0062] gNBs 180a, 180b, 180c can be configured to communicate with WTRUs 102a, 102b, 102c in a stand-alone configuration and / or a non-stand-alone configuration. In the stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c without accessing other RANs (e.g., such as evolved Node Bs 160a, 160b, 160c). In the stand-alone configuration, WTRUs 102a, 102b, 102c can use one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In the non-stand-alone configuration, WTRUs 102a, 102b, 102c can communicate with or be connected to gNBs 180a, 180b, 180c while also communicating with or being connected to other RANs (such as eNode-Bs 160a, 160b, 160c). For example, WTRUs 102a, 102b, 102c can implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more evolved Node Bs 160a, 160b, 160c substantially simultaneously. In the non-stand-alone configuration, evolved Node Bs 160a, 160b, 160c can be used as a mobility anchor for WTRUs 102a, 102b, 102c, and gNBs 180a, 180b, 180c can provide additional coverage and / or throughput for serving WTRUs 102a, 102b, 102c.

[0063] Each of gNBs 180a, 180b, 180c can be associated with a specific cell (not shown) and can be configured to handle radio resource management decisions, handover decisions, scheduling of users in 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 Figure 1D shown, gNBs 180a, 180b, 180c can communicate with each other via the Xn interface.

[0064] Figure 1DThe CN 106 shown may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possibly data networks (DN) 185a, 185b. Although the foregoing elements are depicted as part of the CN 106, it should be understood that any of these elements may be owned and / or operated by entities other than the CN operator.

[0065] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selection of a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing in order to customize CN support for the WTRUs 102a, 102b, 102c based on the type of service used by the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low-latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for machine type communication (MTC) access, etc. The AMF 182a, 182b may provide control plane functions for handover between the RAN 104 and other RANs (not shown) employing other radio technologies such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0066] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 106 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 106 via the N4 interface. The SMF 183a, 183b may select and control the UPFs 184a, 184b and configure the traffic routing through the UPFs 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0067] The UPFs 184a, 184b can be connected via the N3 interface to one or more of the gNBs 180a, 180b, 180c in the RAN 104, and these gNBs can provide the WTRUs 102a, 102b, 102c with access to a packet switched network (such as the Internet 110) to facilitate communication between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b can perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0068] The CN 106 can facilitate communication with other networks. For example, the CN 106 can include an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108 or can communicate with the IP gateway. Additionally, the CN 106 can provide the WTRUs 102a, 102b, 102c with access to other networks 112, which can include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c can be connected to the DNs 185a, 185b via the UPFs 184a, 184b through the N3 interface to the UPFs 184a, 184b and the N6 interface between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0069] In view of Figures 1A to 1D and Figures 1A to 1D In view of the corresponding descriptions, one or more or all of the functions described herein with reference to one or more of the following can be performed by one or more emulation devices (not shown): WTRUs 102a-d, base stations 114a-b, evolved Node Bs 160a-c, MMEs 162, SGWs 164, PGWs 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a-b, SMFs 183a-b, DNs 185a-b, and / or any other device described herein. The emulation device(s) can be one or more devices configured to mimic one or more or all of the functions described herein. For example, the emulation device(s) can be used to test other devices and / or simulate network and / or WTRU functions.

[0070] A simulation device can be designed to implement one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, the one or more simulation devices can perform one or more or all functions while being 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. The one or more simulation devices can perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device can be directly coupled to another device for testing purposes and / or perform tests using over-the-air wireless communication.

[0071] The one or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test laboratory and / or a test scenario in a non-deployed (e.g., test) wired and / or wireless communication network to implement tests of one or more components. The one or more simulation devices can be test devices. Direct RF coupling and / or wireless communication via an RF circuit (e.g., which can include one or more antennas) can be used by the simulation device to transmit and / or receive data.

[0072] Operation in an unlicensed band may be subject to some limitations on transmit power control (TPC), the radio front-end (RF) output power and power density given by the average effective isotropic radiated power (EIRP), and the average EIRP density at the maximum power level. It may be further subject to requirements on out-of-band emissions of the transmitter. The foregoing may be specific to a frequency band and / or a geographical location.

[0073] Operation may be further subject to requirements on the nominal channel bandwidth (NCB) and the occupied channel bandwidth (OCB) defined for the unlicensed spectrum in the 5 GHz region. The NCB, which is the widest frequency band including the guard bands assigned to a single channel, can always be at least 5 MHz. The OCB, which is the bandwidth containing 99% of the signal power, can be between 80% and 100% of the declared NCB. During an established communication, a device can be allowed to temporarily operate in a mode where its OCB can be reduced to as low as 40% of its NCB and a minimum of 4 MHz.

[0074] Channel access in an unlicensed band generally can use a listen-before-talk (LBT) mechanism. LBT generally can be enforced independently of whether the channel is occupied.

[0075] For frame-based systems, LBT can be characterized by one or more of the following: clear channel assessment (CCA) time (e.g., about 20 μs), channel occupancy time (e.g., minimum 1 ms, maximum 10 ms), idle period (e.g., minimum 5% of the channel occupancy time), fixed frame period (e.g., equal to the channel occupancy time plus the idle period), short control signaling transmission time (e.g., 5% maximum duty cycle within a 50 ms observation period), and CAA energy detection threshold, etc. Generally, a 50 ms observation period can be divided into multiple duty cycles (e.g., 5%, 10%, 20%, 40%, 60%, etc.). Here, x% represents the percentage of time during which the LTE network is transmitting signals.

[0076] For load-based systems (e.g., the transmission / reception structure may not be fixed in time), LBT can be characterized by a quantity N corresponding to the number of idle slots in the extended CCA rather than a fixed time period. N can be randomly selected within a certain range.

[0077] Deployment can include different independent NR-based operations, different variants of dual-connectivity operations, e.g., E-UTRAN New Radio Dual Connectivity (EN-DC) with at least one carrier operating according to the LTE radio access technology (RAT) or NR DC with at least two sets of one or more carriers operating according to the NR RAT, and / or different variants of carrier aggregation (CA), e.g., may also include different combinations of zero or more carriers in each of LTE and NR RAT.

[0078] For example, for LTE, the following functionality has been considered for the Licensed-Assisted Access (LAA) system: LBT before clear channel assessment discontinuous transmission on a carrier, which has a limited maximum transmission duration, carrier selection, transmission power control (TPC), radio resource management (RRM) measurements (including cell identification), and channel state information (CSI) measurements (including channels and interference). The functionality mentioned above will be described in detail below.

[0079] The LBT procedure can be defined as a mechanism by which the equipment can apply a CCA check before using the channel. CCA can determine the presence or absence of other signals on the channel at least by using energy detection, so as to determine whether the channel is occupied or idle respectively. European and Japanese regulations require the use of LBT in the unlicensed band. In addition to regulatory requirements, carrier sensing via LBT can be a method for fair sharing of the unlicensed spectrum, and thus is considered an important feature for fair and friendly operation in the unlicensed spectrum within a single global solution framework.

[0080] In unlicensed spectrum, channel availability may not always be guaranteed. In addition, continuous transmission is prohibited in some regions (such as Europe and Japan), and limits are imposed on the maximum duration of transmission bursts in unlicensed spectrum. Therefore, discontinuous transmission with a limited maximum transmission duration may be a required functionality for LAA.

[0081] Due to the existence of unlicensed spectrum with a large available bandwidth, LAA nodes may need carrier selection to select carriers with low interference and achieve good coexistence with other unlicensed spectrum deployments through low interference.

[0082] TPC is a regulatory requirement in some regions where the transmission device may be able to reduce its transmission power by 3 dB or 6 dB compared to the maximum nominal transmit power. This requirement may not require new specifications.

[0083] RRM measurements including cell identification enable mobility between SCell and robust operation in the unlicensed band.

[0084] A WTRU operating on an unlicensed carrier can also support the necessary frequency / time estimation and synchronization to enable RRM measurements and successfully receive information on the unlicensed band.

[0085] 3GPP has initiated a work item to support NR operation in the unlicensed band. One of the objectives is to specify NR-based operation in the unlicensed spectrum, including initial access, scheduling / hierarchical hybrid automatic repeat request (HARQ), and mobility, as well as coexistence methods with LTE-LAA and other existing RATs. Deployment scenarios can include different stand-alone NR-based operations, different variants of dual-connectivity operations, such as 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, and / or different variants of carrier aggregation (CA), such as different combinations that may also include zero or more carriers of each of the LTE and NR RATs.

[0086] New Radio Unlicensed (NR-U) can support four categories of channel access schemes for NR-U operation. Category 1 can include transmission immediately after a short switching gap. Category 2 can include LBT without random backoff. Category 3 can include LBT with random backoff with a fixed contention window size. Category 4 can include LBT with random backoff with a variable contention window size.

[0087] It has also been agreed to use clear channel assessment to perform LBT on the so-called 20 MHz LBT sub-band. The bandwidth part (BWP) can be a single LBT sub-band or can be composed of multiple LBT sub-bands.

[0088] The time for which a channel has been acquired for transmission can be considered the Channel Occupancy Time (COT). The COT can be acquired by the WTRU or by the base station and can subsequently be shared with another node. The total COT duration (including any sharing) shall not exceed the maximum COT.

[0089] Different embodiments according to the present application will be described below. In the present application, in view of the fact that channel acquisition failure may affect the presence of some CSI-RS transmissions, different solutions for WTRU with incomplete CSI-RS operations are disclosed. The solutions disclosed herein can be applicable to any type of RS (not only CSI-RS) and can be applicable to any signal desired by the WTRU that may not be present due to failure to acquire the channel to be transmitted by the gNB.

[0090] A first embodiment will be described below. In the first embodiment, in order to determine whether CSI-RS has been transmitted, the WTRU can determine the presence of CSI-RS resources. That is, the WTRU can be configured with CSI-RS resources for expected periodic or semi-persistent CSI-RS, and the WTRU can determine the actual presence of the CSI-RS resources before performing measurements or before feeding back such measurements in order to determine whether CSI-RS has been transmitted. In this embodiment, the WTRU can determine the presence of CSI-RS by one or more of the following items: (1) an explicit indication of the presence of CSI-RS resources, (2) an implicit indication of the presence of CSI-RS resources, (3) determining the presence of CSI-RS based on WTRU measurements, and (4) determining the presence of CSI-RS based on a condition being met. The above items and different solutions related to these items will be described with reference to specific embodiments below.

[0091] The solutions related to the explicit indication of the presence of CSI-RS resources will be described below. To determine whether CSI-RS has been transmitted, the WTRU may receive an indication from the network. For example, the WTRU may receive an indication from the gNB that provides an explicit list of the CSI-RS resources that have been transmitted. Such an indication may represent all of the CSI-RS resources expected during a certain time period prior to the indication being received by the WTRU. The indication may be a bitmap of all of the expected CSI-RS or a toggle bit indicating the CSI-RS resources that have been transmitted. In another example, the indication may provide a list of CSI-RS index values and / or a list of the times at which CSI-RS has actually been transmitted. In the present application, unless otherwise specified, the terms "CSI-RS" and "CSI-RS resource" may be used interchangeably. It should be understood that since the indication is provided by the network, it is explicit to the WTRU (i.e., the WTRU does not have to process the indication much to obtain the information it needs), and thus the indication may be considered an "explicit" indication as opposed to the "implicit" indication discussed below.

[0092] In another example, the indication may provide a list of the time resources (e.g., time slots) during which the base station (i.e., the gNB) performs transmissions. The WTRU may use the indication as a mask for all possible CSI-RS transmissions and determine that CSI-RS is transmitted only during the time slots in which the base station performs transmissions. Such an indication may be used as a post-time slot blanking mode. The WTRU may use the time slot blanking mode to better determine the time slots in which CSI-RS has been transmitted or in which interference can be measured. This may enable the WTRU to report two-step interference measurements: interference measurements during the active COT and interference measurements outside of the COT. Such values may help determine the presence of hidden nodes and the probability of acquiring the channel.

[0093] Reference will be made to Figure 2 the above indication will be further described. Figure 2 is a diagram showing an indication of the presence of CSI-RS resources. As Figure 2 shown, the WTRU may be configured with CSI-RS and channel state information interference measurement (CSI-IM) every m time slots. The WTRU may then receive an indication of the previous time slot (e.g., in time slot 2m+3) in which CSI-RS was indeed transmitted by the network. Based on the indication, the WTRU may determine the appropriate reference time slot for an upcoming CSI feedback report. In addition, the WTRU may divide the CSI-IM into two groups, one group that occurs when its serving cell has acquired an unlicensed channel (e.g., in time slots 0 and m), and another group that occurs when the serving cell has not acquired the channel (e.g., in time slot 2m). The WTRU may obtain different reports (e.g., different interference measurement reports) based on these two types of CSI-IM and may feedback multiple values.

[0094] In an embodiment, an indication of the actual transmission of CSI-RS may be received by the WTRU in a periodic CSI request. Such a request may point to a specific transmission occasion of a CSI-RS resource, and the WTRU may assume that any transmission occasion of the CSI-RS resource indicated in the periodic CSI request is actually transmitted by the gNB.

[0095] Solutions related to an implicit indication of the presence of a CSI-RS resource will be described below. In an embodiment, the implicit indication may be a parameter of a subsequent CSI-RS transmission. That is, the WTRU may determine the presence of a previous CSI-RS based on parameters of a subsequent CSI-RS transmission (e.g., a subsequent CSI-RS). For example, the parameters of the CSI-RS may cycle through some configured values upon each successful transmission. The WTRU may attempt to blindly decode the current CSI-RS using different possible parameters. When an appropriate parameter for the current transmission (e.g., the current CSI-RS) is detected, the WTRU may determine whether a previous CSI-RS resource has actually been transmitted. The CSI-RS parameters that may cycle may include at least one of the following: sequence, CSI-RS resource mapping, antenna port, orthogonal cover code, etc.

[0096] In an embodiment, the implicit indication may be a sequence of consecutive CSI-RS resources, i.e., the WTRU may be configured with CSI-RS resources having four possible seeds to generate a sequence. The seeds may cycle every four transmissions. The WTRU may be able to determine whether up to three consecutive CSI-RS resources have not been transmitted (e.g., due to a channel acquisition failure).

[0097] Reference will be made to Figure 3 further describe the above implicit indication. Figure 3 It shows that the WTRU determines whether there is a previous CSI-RS based on the sequence of the currently received CSI-RS. As Figure 3 shown, at 301, the WTRU receives CSI-RS at each configured occasion, and the WTRU performs detection by cycling through 4 sequences. At 302, the WTRU does not detect CSI-RS in time slot m or time slot 2m. Then, the WTRU may receive CSI-RS with sequence 2 in time slot 3m. This may indicate to the WTRU that CSI-RS was indeed not transmitted in time slots m and 2m. This may also be used by the WTRU to determine a reference time slot for future CSI feedback reports. At 303, the WTRU does not detect CSI-RS in time slot m or time slot 2m. Then, the WTRU may receive CSI-RS with sequence 3 in time slot 3m. This may indicate to the WTRU that it missed the transmitted CSI-RS (i.e., CSI-RS with sequence 2) in time slot m or time slot 2m. It should be understood thatFigure 3 The above examples of the 4 sequences for CSI-RS transmission shown are not intended to be exclusive or limiting of the present application. Any other sequences can be used as long as they may contribute to the realization of the principles of the present application.

[0098] In an embodiment, the WTRU may not be able to determine which time slot has an undetected CSI-RS and may not be able to use that information to determine appropriate measurements based on previously assumed non-transmitted CSI-RS. In other embodiments, the parameters of the CSI-RS can be modified to enable the WTRU to determine the specific time slot in which the CSI-RS is missing. For example, the sequence of subsequent CSI-RS can be determined based on whether one or more previous CSI-RS have been skipped and the time slots that have been skipped.

[0099] Solutions related to determining the presence of CSI-RS based on WTRU measurements will be described below. The WTRU can determine the presence of CSI-RS based on measurements made on the resources where the WTRU expects CSI-RS. For example, the WTRU can perform signal-to-interference-plus-noise ratio (SINR) measurements, and any value below a threshold can cause the WTRU to assume that CSI-RS has not been transmitted on the resource. The threshold can be configurable.

[0100] In another embodiment, the WTRU can perform channel acquisition measurements (e.g., clear channel assessment) before transmitting on the expected CSI-RS resources. The WTRU can determine whether the channel is busy before the CSI-RS transmission. If the WTRU determines that the channel is busy before the transmission of the expected CSI-RS resources, it can assume that the CSI-RS resources have not been transmitted in that instance. Generally, the above determination can be performed by a processor in the WTRU. In the present application, unless otherwise stated, the processes performed by the WTRU can generally be performed by its processor.

[0101] The WTRU can assume that a CSI-RS resource is present only if a condition is met. In an embodiment, if the transmission timing of the CSI-RS resource coincides with at least one of the other transmissions from the gNB and there is one of the other transmissions, the WTRU can assume that the CSI-RS resource has also been transmitted. For example, the WTRU can be configured with a signal, such as a demodulation reference signal (DMRS), to be transmitted in combination with the CSI-RS. If the WTRU successfully detects the associated DMRS, the WTRU can assume that the CSI-RS has also been transmitted.

[0102] In an embodiment, the WTRU may assume that CSI-RS exists only when it is transmitted on the resources of an active COT. For example, the WTRU may assume a CSI-RS occasion that appears on the LBT sub-band of an active COT. Thus, the WTRU may determine the existence of CSI-RS resources based on an indication of the COT structure that may be received before the transmission occasion of the CSI-RS.

[0103] A second embodiment will be described below. The second embodiment relates to increasing the robustness of CSI-RS transmission in the case where CSI-RS is missing due to a channel acquisition failure. The increased robustness of CSI-RS transmission can be achieved by increasing the transmission periodicity or the probability of semi-persistent CSI-RS. To increase the probability of transmitting CSI-RS, the WTRU may be configured to have multiple transmission occasions bound to a single CSI-RS transmission. In this case, the WTRU may not expect to transmit a single CSI-RS transmission on more than one occasion. Thus, in the second embodiment, when determining that the CSI-RS resource has indeed been transmitted in a transmission occasion, the WTRU may not need to continue monitoring other occasions (i.e., conditional occasions) bound to the CSI-RS transmission, and when determining that the CSI-RS resource has not been transmitted in the transmission occasion, the WTRU may need to continue monitoring other occasions bound to the CSI-RS transmission.

[0104] The second embodiment will be described below with reference to Figures 4A to 4B in detail. Figure 4A is a flowchart showing a method 400 according to the second embodiment. As Figure 4A shown, the method 400 may include: at 401, obtaining a transmission occasion of the CSI-RS; at 402, obtaining at least one conditional transmission occasion of the CSI-RS; and at 403, determining whether the CSI-RS is transmitted in the transmission occasion, wherein in the case where the CSI-RS is not transmitted in the transmission occasion, at 404, detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission occasions. The above processes 401 to 404 will be described below with reference to specific examples.

[0105] Thus, the WTRU may include a processor. The processor is configured to obtain a transmission occasion for a channel state information reference signal (CSI-RS); obtain at least one conditional transmission occasion of the CSI-RS; and determine whether the CSI-RS is transmitted in the transmission occasion. In the case where the CSI-RS is not transmitted in the transmission occasion, the processor is further configured to detect whether the CSI-RS is transmitted in one of the at least one conditional transmission occasions.

[0106] As Figure 4AAs shown, at 401, method 400 may include obtaining a transmission occasion of CSI-RS.

[0107] The transmission occasion can be obtained without further processing. In an embodiment, the transmission occasion may be pre-stored in the memory of the WTRU, and the WTRU may retrieve the transmission occasion from the memory. In an embodiment, the transmission occasion can be obtained from the network. In an embodiment, the transmission occasion can be obtained from a base station other than the serving base station or a third-party device. It should be understood that the above embodiments regarding different sources of the transmission occasion are not intended to be exclusive or limiting to the present application.

[0108] The transmission occasion can be obtained through additional processing. In an embodiment, the transmission occasion can be obtained by processing one or more parameters. The parameters may include a reference time slot or a default time slot, a timing offset, a periodicity, etc. Processing at least one parameter can obtain the transmission occasion.

[0109] For example, at 401, the process of determining the transmission occasion of CSI-RS may further include: obtaining a transmission occasion configuration including a timing offset and a periodicity; and determining the timing of the transmission occasion based on the timing offset and the periodicity. Thus, the WTRU may be configured to obtain a CSI-RS transmission occasion configuration including a timing offset and a periodicity, and determine the timing of the transmission occasion based on the timing offset and the periodicity. In other words, such an offset and a periodicity may enable the WTRU to determine the timing of each CSI-RS resource occasion of the CSI-RS configuration.

[0110] The transmission occasion configuration can be obtained in the same or a similar manner as the above-described transmission occasion. For example, the transmission occasion configuration can be obtained from the network, a base station, a third-party device, or the memory of the WTRU. The present application also does not limit the source of the configuration as long as the configuration may contribute to the principles of the present application.

[0111] The timing offset and the periodicity in the transmission occasion configuration can be used to determine the timing of the transmission occasion. The timing offset may represent a timing offset value relative to a reference timing (e.g., a reference time slot). The periodicity may represent the length between two consecutive transmission occasions, i.e., the number of time slots within the transmission occasion periodicity. For example, the value of the timing offset is 0, and the value of the periodicity is m. In this case, the WTRU may determine the transmission occasion as time slot 0, time slot m, time slot 2m, etc. Thus, the timing of the transmission occasion can be obtained. It should be understood that the above timing offset and periodicity and their values are given as examples, and they are not intended to be exclusive or limiting to the present application. The above processing at 401 will be further described below with reference to Figure 4B Further describe the processing at 401 above.

[0112] As shown in Figure 4, method 400 may include: at 402, obtaining at least one conditional transmission occasion of CSI-RS. That is, the WTRU may obtain one or more conditional transmission occasions associated with the CSI-RS transmission occasion obtained at 401.

[0113] The at least one conditional transmission occasion can be obtained without any further processing. The at least one conditional transmission occasion can be obtained in the same or similar manner as the above-mentioned transmission occasion. For example, the at least one conditional transmission occasion can be obtained from a network, a base station, a third-party device, or the memory of the WTRU. The present application does not limit the source of the conditional transmission occasion as long as it helps to implement the principles of the present application.

[0114] The at least one conditional transmission occasion can be obtained through additional processing. In an embodiment, the at least one conditional transmission occasion can be obtained by processing one or more parameters. The parameters may include a reference time slot or a default time slot, a timing offset, a periodicity, etc. Processing the at least one parameter can obtain the transmission occasion.

[0115] For example, at 402, the process of obtaining at least one conditional transmission occasion of CSI-RS may further include: obtaining a conditional transmission occasion configuration including at least one conditional timing value; and determining the at least one conditional transmission occasion based on the at least one conditional timing value. Therefore, in order to obtain at least one conditional transmission occasion of CSI-RS, the processor is further configured to obtain a conditional transmission occasion configuration including at least one conditional timing value, and determine at least one conditional transmission occasion based on the at least one conditional timing value.

[0116] The conditional transmission occasion configuration may indicate one or more conditional timing values associated with the CSI-RS transmission occasion obtained at 401. Such conditional timing values may provide resources for one or more conditional CSI-RS transmissions (e.g., at least one conditional transmission occasion). For example, there is a conditional timing value, i.e., 5, in the conditional transmission occasion configuration, indicating that the conditional transmission occasion is the 5th time slot after the transmission occasion obtained at 401. For example, there are two conditional timing values, i.e., 5 and 9, in the conditional transmission occasion configuration. In this case, there are two conditional transmission occasions after the transmission occasion obtained at 401, i.e., the 5th time slot and the 9th time slot. It should be understood that the above examples of conditional timing values are given by way of illustration only, and they are not intended to be exclusive or limiting to the present application. The conditional transmission occasion will be further described below with reference to Figure 4B The conditional transmission occasion is further described.

[0117] In an embodiment, the conditional transmission occasion configuration and the above-mentioned transmission occasion configuration can be combined into a single configuration. That is, the WTRU can obtain a single configuration that includes the transmission occasion configuration required for the processing at 401 and the conditional transmission occasion configuration required for the processing at 402. Therefore, the above parameters, such as timing offset, periodicity, and conditional timing values, can be included in this single configuration.

[0118] The conditional transmission occasion is used for the transmission of CSI-RS, and it is for the condition that the previously associated timing (e.g., the transmission occasion obtained at 401, the previous conditional transmission occasion obtained at 402) is not used for CSI-RS transmission. In this application, unless otherwise specified, the terms "transmission occasion", "CSI-RS transmission occasion", "CSI-RS transmission", and "CSI-RS occasion" can be used interchangeably, while the terms "conditional transmission occasion", "CSI-RS conditional transmission occasion", "CSI-RS conditional transmission", and "CSI conditional transmission occasion" can be used interchangeably.

[0119] As Figure 4A shown, after the processing at 401, the WTRU can determine that the timing offset is 0 and the periodicity is m, and can also determine to configure the CSI-RS transmission occasion every m time slots, the first CSI-RS transmission occasion is time slot 0, and the next CSI-RS transmission occasion is time slot m. In addition, after the processing at 402, the WTRU can determine that each CSI-RS transmission occasion is configured with two conditional timing values, that is, 5 and 9. Therefore, the WTRU can determine that the corresponding conditional transmission occasions relative to time slot 0 are time slot 5 and time slot 9, and the corresponding conditional transmission occasions relative to time slot m are time slot m + 5 and time slot m + 9.

[0120] Then, the method 400 can proceed to the processing at 403. At 403, the method 400 can include determining whether to transmit the CSI-RS in this transmission occasion. In the case where the CSI-RS is not transmitted in this transmission occasion, at 404, it is detected whether the CSI-RS is transmitted in one of at least one conditional transmission occasion. The method 400 can also include, under the condition that the CSI-RS is transmitted in the transmission occasion (i.e., at 403), at 405, not detecting whether the CSI-RS is transmitted in one of at least one conditional transmission occasion.

[0121] If the CSI-RS is not transmitted in (1) an associated fixed transmission occasion and (2) any previous conditional transmission occasion associated with the same fixed transmission occasion, the WTRU may only need to attempt the CSI-RS in the conditional transmission occasion. For example, if the WTRU does not detect the CSI-RS in slot 0, it monitors the CSI-RS in slot 5. Once the CSI-RS is detected in slot 5, it may not be necessary to monitor the CSI-RS transmission in slot 9. In slot m, if the WTRU detects the CSI-RS, it may not be necessary to monitor any associated conditional transmission occasions in slots m+5 and m+9. If the WTRU detects the CSI-RS in a slot, the WTRU may assume that the resources mapped to subsequent conditional CSI-RS (e.g., associated with the detected CSI-RS resources) can be reused for the transmission of other signals or channels. For example, the RE mapping of the transmission overlapping with the transmitted conditional CSI-RS may require puncturing (or rate matching) of the resources of the conditional CSI-RS. The RE mapping of the transmission overlapping with the resources of the non-transmitted conditional CSI-RS may not require puncturing (or rate matching) of the resources of the conditional CSI-RS.

[0122] In a second embodiment, the WTRU may detect the CSI-RS in the transmission occasion and the conditional transmission occasion by the method disclosed in the first embodiment above. For example, the WTRU may determine whether the CSI-RS is transmitted based on an indication of the presence of the CSI-RS resource. As another example, the WTRU may determine whether the CSI-RS is transmitted by detecting whether the channel is busy before the transmission occasion. Different detection methods for CSI-RS transmission may refer to the first embodiment above.

[0123] In the example shown in FIG. 4, slot 0 is used as a reference slot, and thus if the timing offset is 0, the reference slot will be used as the transmission occasion for the CSI-RS. It should be understood that the reference slot can be any other available slot. In addition, when the CSI-RS conditional timing value is configured, the WTRU may use any CSI-RS occasion or any CSI-RS conditional occasion associated with the original reference slot bound to the feedback measurement as the reference slot for the feedback measurement.

[0124] In an embodiment, the WTRU may perform measurements on the CSI-RS transmission occasion, and depending on whether the measurements meet a criterion (e.g., a threshold), the WTRU may determine whether to attempt to detect the CSI-RS in the upcoming associated conditional transmission occasion. Considering that the WTRU can autonomously determine the resources for providing CSI measurements, the WTRU may indicate to the network the resources (original occasion or conditional occasion) it uses when providing the feedback measurement. This may enable the network to determine whether the WTRU is affected by the hidden mode.

[0125] In an embodiment, a WTRU may be configured with CSI-RS resources, and the timing of their transmission opportunities may depend on another transmission. That is, the transmission opportunity obtained at 401 may be determined based on another transmission. For example, the WTRU may expect to determine the CSI-RS transmission opportunity to be determined based on the timing of an associated DMRS transmission or an associated DRS (discovery reference signal) transmission. Given that the DMRS transmission or DRS transmission may be transmitted at any time during a preconfigured window, the timing of the associated CSI-RS may vary according to the actual time of the DMRS transmission or DRS transmission. It should be understood that the DMRS transmission and DRS transmission discussed above are given by way of example only, and they are not intended to be exclusive or limiting to the present application. The transmission opportunity obtained at 401 may also depend on any other available transmission as long as the transmission helps to implement the principles of the present application.

[0126] In an embodiment, a WTRU may be configured with CSI-RS resources for which at least one transmission parameter (e.g., timing, bandwidth, sequence, etc.) may depend on at least one parameter. That is, the CSI-RS transmission (e.g., CSI-RS timing, CSI-RS frequency, number of ports for CSI-RS transmission during a COT, structure of CSI-RS per resource block, etc.) may be determined based on at least one other parameter. The at least one other parameter may include COT timing (e.g., start timing of the COT), density of CSI-RS transmission, etc. At least one other parameter that may be used to determine the CSI-RS transmission opportunity will be described below with reference to specific examples.

[0127] For example, the CSI-RS transmission opportunity may be determined based on the start timing of the COT. In such examples, the CSI-RS resources associated with the CSI-RS transmission opportunity may be configured with an offset based on the start timing of the COT. The CSI-RS resources may also be configured with a periodicity based on the COT duration. Since the start timing of the COT may vary, the CSI-RS transmission opportunity may also vary. In the present application, unless otherwise stated, the start timing of the COT may also be referred to as the COT timing.

[0128] In some cases, such variable timing may cause the CSI-RS transmission to conflict with other transmissions. For example, variable timing CSI-RS may conflict with non-variable timing CSI-RS, DRS, control resource set (CORESET), or DMRS. In such cases, the WTRU may use a possibly configured transmission priority to determine the location where the CSI-RS is expected to be present at a given time. For example, the CSI-RS resources may have an index, and in case of a conflict, the WTRU may only expect the presence of the CSI-RS with the highest or lowest index value.

[0129] The WTRU may expect that all types of CSI-RS use variable timing. For example, zero-power (ZP) CSI-RS for physical downlink shared channel (PDSCH) mapping may also be shifted according to the COT timing and / or duration.

[0130] The WTRU may be configured with a reporting configuration associated with one or more resource sets, the one or more resource sets indicating a set of downlink resources on which CSI measurements should be performed. However, due to the uncertainty of LBT and the start timing of the COT, the network may not shift the CSI-RS transmission or switch to another time symbol / slot / frame, and / or adjust the CSI-RS density in the frequency domain. It may also modify the per-resource-block structure of the CSI-RS transmission.

[0131] In an embodiment, the CSI-RS transmission may be determined based on the per-resource-block structure of the CSI-RS resources within the COT. For example, the CSI-RS resources associated with the CSI-RS transmission occasion may be configured with a CSI-RS resource mapping corresponding to the density of the CSI resources. That is, the transmission occasion configuration obtained at 401 may also include a CSI-RS resource mapping corresponding to the density of the CSI resources. The density of the CSI resources may be defined as the number of resource elements per resource block (N). Based on the result of LBT (e.g., the duration of the COT, the obtained bandwidth, etc.), the base station may reduce the number of ports for a given CSI-RS transmission during the COT. For this purpose, the CSI-RS configuration may consist of M aggregation sizes - x i as shown in Equation 1 below.

[0132]

[0133] Here, M represents the full-size CSI-RS resources configured by RRC. Different aggregation levels may be indexed from 1 to M.

[0134] In an embodiment, the density reduction may be explicit. The WTRU receives the density of the CSI resources during the COT in the aperiodic trigger state. The WTRU may also receive DCI with a dedicated DCI field for activating one aggregation level at the start of the COT.

[0135] In an embodiment, the density reduction may be implicit. The WTRU may be configured with a mapping between the aggregation level and the COT duration. For example, the WTRU may initially be configured with size - x M CSI resources for a COT duration T longer than K slots, with the size reduced to size - xM-1 when V ≤ T < K, and the size reduced to size - when W ≤ T < VxM-2 etc. When the duration of the acquired channel is very short, this can be used to make the network prioritize one type of transmission (e.g., PDSCH for a high - demand WTRU) over CSI - RS transmission.

[0136] Similarly, the implicit density reduction can be performed by the WTRU based on the identification of the sub - bands acquired during the COT. A similar mapping between the acquired sub - bands and the CSI resource density can be configured for the WTRU.

[0137] In an embodiment, the CSI - RS transmission can be determined based on the density of the CSI - RS transmission. For example, the per - resource - block structure outlined above may need to adapt to the COT start timing. For example, if the COT starts in the middle of a time slot, the structure can switch to one or more symbols within a given RB that transmits CSI - RS. Thus, the WTRU can maintain the same CSI structure (i.e., the same frequency, time - division, and code - division) for each resource block, but only apply a time offset to the start of the CSI - RS transmission within a given RB. The WTRU can apply this switch only to the first time slot of the COT or further apply it to multiple time slots of the COT.

[0138] In the case of periodic CSI - RS transmission, the WTRU can assume that the configured CSI - RS transmission occurs once every Nth time slot.

[0139] Similarly, as described above, the WTRU can be configured with a mapping of the COT duration and the time when the CSI - RS transmission occurs. If the COT duration is greater than K time slots, the WTRU can expect a CSI - RS transmission with N - periodicity (e.g., every Nth time slot). If the COT duration is less than K time slots, the WTRU can, for example, expect a CSI - RS transmission with N - T periodicity (i.e., every N - T time slots), where T can be a configurable value or can be determined as a function of K. This modification of the time structure can also be signaled by the network via downlink control information (DCI) at the start of the COT.

[0140] In an embodiment, the density of the CSI - RS transmission in frequency can be modified. For example, the per - resource - block structure outlined above may need to be adjusted based on the results of the base - station channel acquisition. For example, CSI - RS can be configured for each RB corresponding to a density equal to 1, corresponding to 1CSI-RS transmission in every two RBs with a density of 1 / 2, etc. The WTRU can be further configured with the relationship between the number of bandwidths obtained in the active DL bandwidth part (BWP) and the density of CSI-RS transmission. For example, if the base station obtains all the subbands of the active DL BWP, the WTRU can expect the lowest density of CSI-RS transmission. While if only a subset of the subbands of the active DL BWP is obtained, the WTRU may expect a higher density of CSI-RS configured within the obtained subbands.

[0141] The WTRU can also expect two different density schemes for CSI-RS transmission inside and outside the COT. If the WTRU has received an indication of channel acquisition indicating that the base station has obtained a set of subbands or the WTRU has obtained a set of subbands (i.e., the scenario within the COT), it can apply the first CSI-RS transmission density. If the WTRU or the base station has not obtained a set of subbands (i.e., the scenario outside the COT), the WTRU can apply the second density scheme.

[0142] The WTRU can be configured with an alternative CSI-RS configuration as an alternative to the resources associated with the reporting configuration of a trigger state that is used by the WTRU only when a set of conditions is met. These conditions can be associated with the transmission of at least one of the following parameters: COT duration, obtained bandwidth, number of previously reported CSI feedbacks, number of untransmitted CSI-RSs, or number of CSI reports skipped due to LBT failure, etc. It should be understood that the above parameters associated with the conditions are not intended to be exclusive or limiting to the present application. The conditions can also be associated with any other parameters as long as these conditions contribute to the implementation of the principles of the present application.

[0143] The configured alternative CSI-RS configuration can have a higher density in terms of time / frequency, for example. For example, the WTRU can be configured with an n-port CSI-RS with a given density (e.g., a single-port CSI-RS with a density of 3, corresponding to 3 REs per RB). If the obtained channel bandwidth and / or duration is below a certain value, or if the WTRU has not been able to perform any measurements on the CSI-RS resources or report feedback for the past n timing instances, the WTRU can apply the n-port CSI-RS.

[0144] In an embodiment, the transmission timing configuration can also include a CSI-RS trigger offset. The CSI-RS trigger offset can indicate the number of time slots between the time slot containing the DCI that triggers a set of aperiodic non-zero power (NZP) CSI-RS resources and the time slot for transmitting the CSI-RS resources.

[0145] CSI-RS resources may have been triggered in a DCI within a COT and transmitted in a slot of the next COT. If the network is unable to obtain a long enough channel, the WTRU may assume that the CSI-RS will be transmitted at the minimum of the COT duration and the CSI-RS triggering offset.

[0146] In an alternative embodiment, if the CSI-RS transmission slot exceeds the maximum number of slots in the COT duration, the WTRU may monitor the CSI-RS with a dedicated granularity. The granularity may be one of the following: (1) a static pre-configured RRC pattern, e.g., every odd slot; or (2) an RRC pre-configured pattern that is a function of different COT durations. For example, for a COT duration of 1 to x slots, the WTRU may monitor the CSI with a first granularity (e.g., every slot), and for a COT duration of x+1 slots to n slots, the WTRU may monitor the CSI with a second granularity (e.g., every odd or even slot); for a COT duration of n+1 slots to y slots, the WTRU may monitor the CSI with a third granularity (e.g., every t slots), etc. It should be understood that the above examples of different granularities are merely exemplary and are not intended to be exclusive or limiting of the present application.

[0147] Measurements based on CSI-RS are described below. A WTRU operating with multiple LBT sub-bands may be configured to perform measurements on one or more CSI-RS resources present in the multiple sub-bands. In one method, the WTRU may expect one or more CSI-RS to be included within a single LBT sub-band. In such cases, the WTRU may report feedback on one or more CSI-RS that includes the LBT sub-band in which the one or more CSI-RS are transmitted. The WTRU may indicate the set of LBT sub-bands for which the reported feedback is obtained. In an alternative embodiment, the WTRU may pad the feedback report to ensure a consistent size regardless of the number of CSI-RS resources actually transmitted.

[0148] In an alternative embodiment, the CSI-RS may span multiple LBT sub-bands. In this case, the WTRU may report measurements on a portion of the transmitted CSI-RS. For example, the WTRU may use sub-band reporting such that each sub-band measurement corresponds to a portion of the CSI-RS present.

[0149] A WTRU may report wideband CSI feedback for multiple portions of CSI-RS where coverage exists. For example, a WTRU may be configured with CSI-RS that spans many (x) LBT subbands. However, the WTRU may receive CSI-RS only in a first LBT subband and a second LBT subband. The WTRU may determine to report wideband CSI feedback, where it is assumed that the wideband bandwidth is the first LBT subband and the second LBT subband (i.e., all subbands in which CSI-RS is received). Wideband feedback is determined only for a set of contiguous LBT subbands. The WTRU may report multiple wideband feedbacks, each for a set of contiguous LBT subbands. The wideband CSI feedback may indicate the set of CSI-RS resources (or LBT subbands) to which the wideband CSI feedback applies.

[0150] Embodiments regarding cross-COT measurements and reporting will be described below. A WTRU may receive CSI-RS resources in a first COT, but only have applicable feedback resources in a subsequent second COT. In such cases, the WTRU may be configured with a validity timer. The WTRU may determine the validity of a feedback report based on the time between CSI-RS reception and the next upcoming valid feedback reporting resource. In this application, unless otherwise stated, the terms "feedback" and "feedback report" may be used interchangeably.

[0151] In an embodiment, a WTRU that measures in a feedback COT based on CSI-RS resources received in a previous COT may provide measurements applicable to COT parameters or feedback COT parameters. For example, a WTRU that receives CSI-RS resources in a first COT consisting of a first set of LBT subbands may only have feedback resources in a second COT consisting of a second set of LBT subbands. The WTRU may report at least one of the following: measurements applicable to the LBT subbands of the first COT, measurements applicable to the LBT subbands of the second COT, or measurements applicable to a set of LCT subbands suitable for the first COT and the second COT. In such an example, if the CSI-RS received in the first COT is applicable to a first set of LBT subbands, a second set of LBT subbands, and a third set of LBT subbands, but the second COT is only valid in the second set of LBT subbands, the WTRU may report measurements only applicable to the second set of LBT subbands.

[0152] Feedback report instances may be bound to a reference time slot or subframe. However, in some cases, CSI-RS may not be present in the reference time slot. Therefore, a WTRU may assume a set of reference time slots is bound to each feedback report instance.

[0153] In one embodiment, the WTRU may report measurements for only a single CSI-RS occasion within a set of reference time slots. The WTRU may use the earliest or latest reference time slot within the set in which the CSI-RS is present as the reference time slot. In another embodiment, the WTRU may perform measurements on a subset of the reference time slots within the set of reference time slots in which the CSI-RS is present. In another embodiment, the WTRU may perform averaged measurements on a subset of the reference time slots within the set of reference time slots in which the CSI-RS is present.

[0154] Even when there is no CSI-RS transmission, the WTRU may report feedback. This may enable AN indication of hidden notes at the WTRU. Such feedback may indicate that no valid measurements are available. In another solution, the WTRU may report interference values without the desired channel measurements applicable to the reference time slot (or set of reference time slots) associated with the CSI-RS resource.

[0155] In one embodiment, the WTRU may request CSI-RS transmission, e.g., if there is no CSI-RS in the set of reference time slots associated with the feedback reporting occasion. The WTRU's request for CSI-RS may be directed to a specific aperiodic / periodic / semi-persistent CSI-RS resource. For example, the WTRU's request may come from a COT obtained by the WTRU, in which case the WTRU may indicate the parameters of the COT to the network in order to activate a CSI-RS with COT timing dependence.

[0156] The WTRU may determine the content of the CSI feedback based on the relative timing of the associated CSI-RS resource and the physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH) resource used for CSI feedback. Additionally, the WTRU may determine the content of the CSI feedback based on parameters associated with the transmission of the CSI-RS and the transmission of the CSI feedback. For example, the WTRU may determine the content of the feedback, and possibly whether to report the feedback, based on whether the CSI-RS resource and the CSI feedback resource are in the same COT. For example, if the CSI feedback resource is in the same COT as the associated CSI-RS resource, the WTRU may provide a full CSI feedback report (e.g., including subband reporting). If the CSI feedback resource is in a COT after the COT in which the associated CSI-RS resource is located, the WTRU may provide a reduced set of CSI reports (e.g., only broadband values).

[0157] In an alternative embodiment, the content of the CSI feedback report may also depend on the time gap between the COT in which the CSI-RS resource is received and the COT in which the CSI feedback is reported. For example, as the time gap increases, the WTRU may reduce the granularity of the feedback report content.

[0158] In an embodiment, PUCCH resources can be dynamically triggered to transmit CSI feedback. Such dynamically triggered PUCCH resources can enable the WTRU to perform CAT1 or CAT2 PBT before accessing an unlicensed channel.

[0159] In an embodiment, the WTRU can be configured with a set of PUCCH resources. If the set of PUCCH resources is dynamically triggered by the base station, the WTRU can use only them. The trigger can indicate to the WTRU the reference time slot from which the feedback report measurements should be obtained. In another solution, the dynamically triggered PUCCH resources can be pre-configured with a reference time slot (or a set of reference time slots) from which the CSI measurements are obtained.

[0160] Unless the WTRU can be scheduled in the DL, the CSI feedback may have no value. For the case where the WTRU does not have valid resources to feedback CSI with the current COT, it may not make sense to obtain a new COT just for transmitting CSI feedback that may not be useful. If the WTRU has been indicated in a previous COT that it can expect more DL data transmissions, the WTRU can (e.g., only can) obtain a COT for the sole purpose of transmitting CSI feedback. For example, the WTRU may have received a transmission in the first COT and may have performed measurements on CSI-RS resources present during the first COT. The WTRU may not have any more feedback resources within the first COT. If the WTRU receives an indication that it may expect more DL data transmissions in subsequent COTs, the WTRU can attempt to obtain a channel before the CSI feedback resources in order to provide relevant CSI feedback information to the base station.

[0161] In an embodiment, the WTRU can obtain a COT and, if the WTRU also needs to transmit HARQ feedback for a previous COT, transmit the CSI feedback. The WTRU can multiplex the CSI feedback with the HARQ feedback. In a variant of the embodiment, considering that the WTRU may subsequently expect another DL transmission, the WTRU can multiplex the CSI feedback only if there is at least one negative acknowledgement (NACK) present in the HARQ feedback.

[0162] If the WTRU is configured to report multiple CSI feedbacks, including a Channel Quality Indicator (CQI), a Channel Resource Indicator (CRI), L1 beam measurement results, a Precoding Matrix Indicator (PMI), a Rank Indicator (RI), a Layer Indicator (LI), the WTRU may need to perform LBT to obtain UL resources to transmit the CSI feedback report and base the content of the feedback report on the result of the LBT or the timing of a successful LBT. For example, if the WTRU is configured to report multiple types of feedback, the WTRU may only report a subset of the configured number of reports. The WTRU may be configured with priorities associated with the report content, which vary according to the result of the LBT. For example, the CRI may have the highest priority, the CQI may have the second priority, the L1-RSRP may have the third priority, the PMI may have the fourth priority, and so on.

[0163] The WTRU may also report the quantity associated with one report instance in different reports based on the amount of UL resources obtained or the LBT result. The WTRU may further indicate to the network the association between two different quantities reported in two different report instances corresponding to the same trigger state.

[0164] The time domain behavior of the CSI-ReportConfig is indicated by the higher layer parameter reportConfigType and can be set to "aperiodic", "semiPersistentOnPUCCH", "semiPersistentOnPUSCH", or "periodic". The WTRU may have an association between the report configuration type and the type of LBT that the WTRU may perform to obtain resources for CSI feedback. For example, if the WTRU is configured with a periodic report on the PUCCH, it may also be configured with a condition that it uses the PUCCH only if it requires an LBT category of 2 or lower. Although the features and elements have been described above in specific combinations, those of ordinary skill in the art will understand that each feature or element may be used alone or in any combination with other features and elements. Additionally, 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 a processor. Examples of computer-readable media include electronic signals (transmitted via 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 the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

[0165] It should be understood that the terms used in this application are for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" may be intended to include a plurality of elements. The terms "comprising" and "including" are intended to include non-exclusive inclusion. Although this application has been described in detail with reference to the foregoing embodiments, it should be understood that the foregoing embodiments may be modified and such modifications do not depart from the scope of this application.

Claims

1. A method for use in a wireless transmit / receive unit (WTRU), the method comprising: Receiving first information indicating a first set of transmission occasions for receiving channel state information reference signal (CSI-RS) transmissions; Receiving second information indicating a second set of transmission occasions for receiving CSI-RS transmissions; And In response to determining that a CSI-RS transmission is not received in a first transmission occasion of the first set of transmission occasions, receiving a CSI-RS transmission in at least one transmission occasion of the second set of transmission occasions, wherein the determination is made by detecting that a channel associated with the first transmission occasion of the first set of transmission occasions is busy immediately before the first transmission occasion of the first set of transmission occasions.

2. The method according to claim 1, further comprising: In response to determining that a CSI-RS transmission is received in a first transmission occasion of the first set of transmission occasions, receiving another CSI-RS transmission in a second transmission occasion of the first set of transmission occasions.

3. The method according to claim 1, wherein determining whether a first CSI-RS transmission is received in the first transmission occasion of the first set of transmission occasions is based on a measurement, an indication received from a base station, or a parameter of another CSI-RS transmission.

4. The method according to claim 1, wherein the second information indicating the second set of transmission occasions for receiving CSI-RS transmissions indicates one or more time offset values from one of the first set of transmission occasions.

5. The method according to claim 1, wherein at least one parameter of the first set of transmission occasions or the second set of transmission occasions is determined based on a parameter associated with a channel occupancy time (COT).

6. The method according to claim 5, wherein the at least one parameter comprises one or more of the following: time and frequency resources, or the number of antenna ports.

7. The method according to claim 1, further comprising transmitting information indicating a feedback report, wherein the content of the feedback report is based on the timing of the received CSI-RS transmissions and the timing of the transmission including the information indicating the feedback report.

8. The method according to claim 7, wherein the information indicating the feedback report provides feedback associated with a CSI-RS transmission received in a time slot, wherein the time slot is one of a plurality of time slots associated with the feedback report.

9. The method according to claim 8, wherein the feedback associated with the CSI-RS transmission received in the time slot includes feedback associated with a plurality of CSI-RS transmissions received in corresponding plurality of time slots.

10. The method according to claim 8, wherein the feedback report comprises one or more of a signal-to-interference-plus-noise ratio (SINR) measurement, a channel quality indicator (CQI), a channel resource indicator (CRI), a precoding matrix indicator (PMI), a rank indicator, or a layer indicator (LI).

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