Receiving method of CSI-RS and CSI feedback in NR-U

Abstract

The present invention discloses a method used in a wireless transmission / reception unit. The method may include: 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, wherein if the CSI-RS is not transmitted in the transmission opportunity, detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities.

Description

[0001] Cross-references to related patent applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 886,159, filed on August 13, 2019, the contents of which are incorporated herein by reference. Background Art

[0003] Transmissions in the New Radio Unlicensed Spectrum (NR-U) depend on acquired channels. Therefore, a signal with a fixed period may not be transmitted at every configured opportunity. 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, signaling overhead is reduced compared to aperiodic CSI-RS. The maximum channel occupancy time (COT) duration means that any reduction in signaling and therefore channel acquisition is beneficial. Another benefit is that the WTRU (wireless transmit / receive unit) may be able to receive CSI-RS even outside the formally defined COT.

[0004] However, a problem that may arise is that the WTRU must determine whether the CSI-RS was actually transmitted in a certain opportunity or whether it was discarded because the channel has not yet been acquired. This is necessary because it may affect the measurements that the WTRU may perform and may lead to incorrect assumptions about the channel characteristics. Such incorrect measurements, assumptions, and measurement feedback may lead to incorrect WTRU scheduling, which may greatly affect system throughput. Furthermore, incorrect measurements may lead to unnecessary feedback reports, which may also degrade overall system performance due to unnecessary channel acquisition. Summary of the invention

[0005] A method used in a wireless transmission / reception unit is disclosed. The method may include: 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, wherein if the CSI-RS is not transmitted in the transmission opportunity, detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities.

[0006] A wireless transmit / receive unit (WTRU) is disclosed. The WTRU may include: a processor configured to obtain a transmission opportunity of a channel state information reference signal (CSI-RS); obtain at least one conditional transmission opportunity of the CSI-RS; and determine whether to transmit the CSI-RS in the transmission opportunity, wherein if the CSI-RS is not transmitted in the transmission opportunity, the processor is further configured to detect whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities.

[0007] As discussed, in order to prevent incorrect measurements and incorrect feedback of measurements, methods are needed to enable the WTRU to determine if a CSI-RS is present. Methods may also be needed to increase the robustness of CSI-RS transmissions given the need to successfully acquire the channel prior to transmission. The WTRU may also need methods to handle measurements and report appropriate values ​​given lost CSI-RS transmissions. In addition, feedback resources may also need to increase robustness given the channel acquisition requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] A more detailed understanding may be obtained from the following description given by way of example in conjunction with the accompanying drawings, in which like reference numerals indicate like elements, and in which:

[0009] Figure 1A is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented;

[0010] Figure 1B It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary wireless transmit / receive unit (WTRU) for use within the communication system shown;

[0011] Figure 1C It is shown that according to one embodiment, Figure 1A A system diagram of an exemplary radio access network (RAN) and an exemplary core network (CN) used within the illustrated communication system;

[0012] Figure 1D It is shown that according to one embodiment, Figure 1A A system diagram of another exemplary RAN and another exemplary CN used in the communication system shown;

[0013] Figure 2 is a diagram showing an indication of the presence of a channel state information reference signal (CSI-RS) resource;

[0014] Figure 3 is a schematic diagram of a WTRU determining whether a previous CSI-RS exists based on a sequence of a currently received CSI-RS; and

[0015] Figure 4A is a flow chart illustrating a method according to an embodiment of the present application; and

[0016] Figure 4B is a diagram of CSI-RS configured in every m-th time slot. DETAILED DESCRIPTION

[0017] Figure 1A 1 is a schematic diagram illustrating an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 100 may employ one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier FDMA (SC-FDMA), zero tail 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.

[0018] like Figure 1AAs shown, the 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), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0019] The communication system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device that is 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 the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an evolved NodeB (eNB), a Home NodeB, a Home evolved NodeB, a next generation NodeB such as a gNodeB (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0020] The base station 114a may be part of the RAN 104, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), a relay node, etc. The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as a cell (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0021] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0022] More specifically, as noted above, the communication system 100 may be a multiple access system and may employ one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 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).

[0023] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0024] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0025] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, for example using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to / from multiple types of base stations (e.g., eNBs and gNBs).

[0026] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile Communications (GSM), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0027] Figure 1AThe base station 114b in the may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish a picocell or a femtocell. As Figure 1A As shown, the base station 114 b may have a direct connection to the Internet 110. Therefore, the base station 114 b may not need to access the Internet 110 via the CN 106.

[0028] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have different quality of service (QoS) requirements, such as different throughput requirements, delay requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions, such as user authentication. Although not described in detail in the specification, the CN 106 may be configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 and / or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also be in communication with another RAN (not shown) that employs GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0029] The CN 106 may also act as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and / or the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0030] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks via different wireless links). Figure 1A The illustrated WTRU 102c may be configured to communicate with the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0031] Figure 1B is a system diagram illustrating an exemplary WTRU 102. Figure 1B As shown, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0032] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, 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 element 122. Although Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0033] 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 an 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 light signals. It should be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0034] Although the transmit / receive element 122 is Figure 1B 1 as a single element, 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 over the air interface 116.

[0035] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. 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.

[0036] The processor 118 of the WTRU 102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit) and may receive user input data therefrom. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from and store data in a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0037] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0038] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or in lieu of the information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0039] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, Module, FM radio unit, digital music player, media player, video game player module, Internet browser, virtual reality and / or augmented reality (VR / AR) device, activity tracker, etc. Peripheral device 138 may include one or more sensors. The sensor may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, orientation sensor, proximity sensor, temperature sensor, time sensor; geographic location sensor, altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor, humidity sensor, etc.

[0040] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and 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 hardware (e.g., a choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be concurrent and / or simultaneous.

[0041] Figure 1C 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As described above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0042] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0043] Each of the 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 the UL and / or DL, etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with one another via an X2 interface.

[0044] Figure 1C The illustrated CN 106 may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (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.

[0045] The MME 162 may be connected to each of the evolved Node-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0046] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0047] The SGW 164 may be connected to the PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0048] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include, or may be in communication with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0049] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments, such a terminal may (eg, temporarily or permanently) use a wired communications interface with a communications network.

[0050] In a representative embodiment, the other network 112 may be a WLAN.

[0051] A WLAN in infrastructure basic service set (BSS) mode may have an access point (AP) for a 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 carries traffic away from the BSS. Traffic originating from outside the BSS and leading to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and leading to a destination outside the BSS may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the BSS may be sent by the AP, for example, wherein the source STA may send traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as point-to-point traffic. Point-to-point traffic may be sent between the source and destination STAs (e.g., directly between them) using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using an independent BSS (IBSS) mode may not have an AP, and STAs (eg, all STAs) within or using the IBSS may communicate directly with each other. The IBSS communication mode may sometimes be referred to herein as an "ad-hoc" communication mode.

[0052] When using the 802.11ac infrastructure operating mode or a similar operating mode, the AP may transmit a beacon on a fixed channel (such as a primary channel). The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be an operating channel of the BSS and may be used by the STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including 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. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0053] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0054] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz and / or 80MHz channels can be formed by combining continuous 20MHz channels. A 160MHz channel can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For the 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be transmitted by transmitting STA. At the receiver of the receiving STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0055] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0056] WLAN systems that can support multiple channels and channel bandwidths such as 802.11n, 802.11ac, 802.11af, and 802.11ah include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from all STAs operating in the BSS. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only the 1MHz operating mode) is transmitting to the AP, all available frequency bands may be considered busy even if most of the available frequency bands remain idle.

[0057] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0058] Figure 1D 1 is a system diagram illustrating the RAN 104 and the CN 106 according to one embodiment. As noted above, the RAN 104 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0059] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 180b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation techniques. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement coordinated multi-point (CoMP) techniques. For example, the WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0060] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable parameter sets. For example, OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or continuously varying absolute time lengths).

[0061] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c while also not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate or connect with the gNBs 180a, 180b, 180c while also communicating or connecting with other RANs, such as eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more evolved Node-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the evolved Node-Bs 160a, 160b, 160c may serve as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0062] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, interworking between DC, NR, and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNB180a, 180b, and 180c can communicate with each other via the Xn interface.

[0063] Figure 1DThe illustrated CN 106 may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and possible data networks (DNs) 185a, 185b. Although the aforementioned 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.

[0064] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c via the N2 interface in the RAN 104 and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c based on the type of services used by the WTRU 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as WiFi.

[0065] 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 UPF 184a, 184b, and configure traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0066] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0067] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the DNs 185a, 185b via the UPFs 184a, 184b via the N3 interfaces to the UPFs 184a, 184b and the N6 interfaces between the UPFs 184a, 184b and the local DNs 185a, 185b.

[0068] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to one or more of the following may be performed by one or more simulation devices (not shown): WTRU102a-d, base station 114a-b, evolved Node B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b and / or any other device described herein. The simulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0069] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, the one or more simulation devices may 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 in order to test other devices within the communication network. The one or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or perform testing using over-the-air wireless communications.

[0070] The one or more simulation devices may 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 may be used in a test scenario in a test lab and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. The one or more simulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) may be used by the simulation device to transmit and / or receive data.

[0071] Operation in unlicensed bands may be subject to some limitations on transmit power control (TPC), radio front end (RF) output power and power density given by average effective isotropic radiated power (EIRP), and average EIRP density at the highest power level. It may be further subject to requirements on transmitter out-of-band emissions. The foregoing may be specific to frequency bands and / or geographic locations.

[0072] Operation may be further subject to the requirements for the Nominal Channel Bandwidth (NCB) and Occupied Channel Bandwidth (OCB) defined for unlicensed spectrum in the 5 GHz region. The NCB, i.e., the widest frequency band including guard bands allocated to individual channels, may always be at least 5 MHz. The OCB, i.e., the bandwidth containing 99% of the signal power, may be between 80% and 100% of the declared NCB. During established communications, a device may be allowed to temporarily operate in a mode where its OCB may be reduced to as low as 40% of its NCB, with a minimum of 4 MHz.

[0073] Channel access in unlicensed bands can typically use a listen-before-talk (LBT) mechanism. LBT can typically be enforced independently of whether the channel is occupied.

[0074] For frame-based systems, LBT may 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% channel occupancy time), fixed frame period (e.g., equal to channel occupancy time plus idle period), short control signaling transmission time (e.g., maximum duty cycle of 5% within a 50 ms observation period), and CAA energy detection threshold, etc. Typically, 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 that the LTE network is transmitting a signal.

[0075] For load-based systems (eg, the transmission / reception structure may not be fixed in time), LBT may be characterized by a number N corresponding to the number of idle slots in the extended CCA rather than a fixed time period. N may be randomly selected within a certain range.

[0076] Deployments may include different standalone NR-based operations, different variants of dual connectivity operations, for example, E-UTRAN New Radio Dual Connectivity (EN-DC) with at least one carrier operating in accordance with an LTE radio access technology (RAT) or NRDC with at least two sets of one or more carriers operating in accordance with an NR RAT, and / or different variants of carrier aggregation (CA), for example, possibly also including different combinations of zero or more carriers of each of the LTE and NR RATs.

[0077] For example, for LTE, the following functionality has been considered for a License Assisted Access (LAA) system: LBT before clear channel assessment discontinuous transmission on a carrier with a limited maximum transmission duration, carrier selection, transmit power control (TPC), radio resource management (RRM) measurements (including cell identification) and channel state information (CSI) measurements (including channel and interference). The above mentioned functionality will be described in detail below.

[0078] The LBT procedure can be defined as a mechanism by which equipment can apply a CCA check before using a channel. CCA can utilize at least energy detection to determine the presence or absence of other signals on the channel in order to determine whether the channel is occupied or idle, respectively. European and Japanese regulations require the use of LBT in unlicensed bands. In addition to regulatory requirements, carrier sensing via LBT can be a method for fair sharing of unlicensed spectrum and is therefore considered an important feature of fair and friendly operation in unlicensed spectrum within the framework of a single global solution.

[0079] In unlicensed spectrum, channel availability may not always be guaranteed. In addition, some regions (such as Europe and Japan) prohibit continuous transmission and impose restrictions on the maximum duration of transmission bursts in unlicensed spectrum. Therefore, discontinuous transmission with limited maximum transmission duration may be a required functionality for LAA.

[0080] Since there is unlicensed spectrum with larger available bandwidth, LAA nodes may need carrier selection to choose a carrier with low interference and achieve good coexistence with other unlicensed spectrum deployments through low interference.

[0081] TPC is a regulatory requirement in some areas where transmitting equipment may be able to reduce its transmit power by 3dB or 6dB compared to the maximum nominal transmit power. This requirement may not require a new specification.

[0082] RRM measurements including cell identity enable mobility between SCells and robust operation in unlicensed bands.

[0083] A WTRU operating in an unlicensed carrier may also support the necessary frequency / time estimation and synchronization to enable RRM measurements and successfully receive information on the unlicensed band.

[0084] 3GPP has initiated a work item to support NR operation in unlicensed bands. One of the goals is to specify NR-based operations in unlicensed spectrum, including initial access, scheduling / hybrid automatic repeat request (HARQ) and mobility, as well as coexistence methods with LTE-LAA and other existing RATs. Deployment scenarios may include different standalone 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), which may also include different combinations of zero or more carriers of each of the LTE and NR RATs.

[0085] New Radio Unlicensed (NR-U) may support four categories of channel access schemes for NR-U operation. Category 1 may include transmission immediately after a short switching gap. Category 2 may include LBT without random backoff. Category 3 may include LBT with random backoff with fixed contention window size. Category 4 may include LBT with random backoff with variable contention window size.

[0086] It has also been agreed to perform LBT using clear channel assessment on a so called 20 MHz LBT sub-band.A bandwidth part (BWP) may be a single LBT sub-band or may consist of multiple LBT sub-bands.

[0087] The time that a channel has been acquired for transmission may be considered the channel occupation time (COT). The COT may be acquired by a WTRU or by a base station and may then be shared with another node. The total COT duration (including any sharing) may not exceed the maximum COT.

[0088] Different embodiments according to the present application are described below. In the present application, different solutions are disclosed for WTRU to operate with incomplete CSI-RS, taking into account that channel acquisition failure may affect the presence of some CSI-RS transmissions. The solutions disclosed herein may be applicable to any type of RS (not just CSI-RS) and may be applicable to any signal expected by the WTRU that may not be present due to failure to acquire a channel to be transmitted by the gNB.

[0089] The first embodiment will be described below. In the first embodiment, in order to determine whether the CSI-RS has been transmitted, the WTRU may determine the existence of CSI-RS resources. That is, the WTRU may be configured with CSI-RS resources that expect periodic or semi-persistent CSI-RS, and the WTRU may determine the actual existence of CSI-RS resources before performing measurements or before feeding back such measurements in order to determine whether the CSI-RS has been transmitted. In this embodiment, the WTRU may determine the existence of CSI-RS through one or more of the following items: (1) an explicit indication of the existence of CSI-RS resources, (2) an implicit indication of the existence of CSI-RS resources, (3) determining the existence of CSI-RS based on WTRU measurements, and (4) determining the existence of CSI-RS based on conditions being satisfied. The above items and different solutions related to these items will be described below with reference to specific embodiments.

[0090] Solutions related to explicit indication of the presence of CSI-RS resources are described below. In order to determine whether a 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 CSI-RS resources that have been transmitted. Such an indication may represent all CSI-RS resources expected within a certain period of time before the indication is received by the WTRU. The indication may be a bitmap of all expected CSI-RS or a toggle bit indicating the transmitted CSI-RS resources. In another example, the indication may provide a list of CSI-RS index values ​​and / or a list of times when the CSI-RS has actually been transmitted. In this application, unless otherwise specified, the terms "CSI-RS" and "CSI-RS resources" may be used interchangeably. It should be understood that since the indication is provided from the network, it is explicit to the WTRU (i.e., the WTRU does not have to process the indication too much to obtain the information it needs), so the indication may be considered an "explicit" indication as opposed to the "implicit" indication discussed below.

[0091] In another example, the indication may provide a list of time resources (e.g., time slots) in which the base station (i.e., gNB) performs transmissions. The WTRU may use this indication as a mask for all possible CSI-RS transmissions and determine that the CSI-RS is transmitted only in the time slots in which the base station performs transmissions. Such an indication may be used as a post-hoc slot blanking pattern. The WTRU may use the slot blanking pattern to better determine the time slots in which the CSI-RS has been transmitted or in which interference may be measured. This may enable the WTRU to report two steps of interference measurements: interference measurements during the active COT and interference measurements outside the COT. Such values ​​may help determine the presence of hidden nodes and the probability of acquiring a channel.

[0092] Reference Figure 2 The above instructions are further described. Figure 2 is a diagram showing an indication of the presence of CSI-RS resources. Figure 2 As shown, the WTRU may be configured with CSI-RS and channel state information interference measurement (CSI-IM) every m timeslots. The WTRU may then receive an indication of the previous timeslot (e.g., in timeslot 2m+3) where the CSI-RS was indeed transmitted by the network. Based on the indication, the WTRU may determine the appropriate reference timeslot for the 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 timeslots 0 and m) and the other group that occurs when the serving cell has not acquired a channel (e.g., in timeslot 2m). The WTRU may obtain different reports (e.g., different interference measurement reports) based on these two types of CSI-IM and may feed back multiple values.

[0093] 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 opportunity of a CSI-RS resource, and the WTRU may assume that any transmission opportunity of the CSI-RS resource indicated in the periodic CSI request is actually transmitted by the gNB.

[0094] Solutions related to implicit indication of the presence of CSI-RS resources are 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 the 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 configuration values ​​at each successful transmission. The WTRU may attempt to blindly decode the current CSI-RS using different possible parameters. Upon detecting appropriate parameters for the current transmission (e.g., the current CSI-RS), the WTRU may determine whether the previous CSI-RS resource has actually been transmitted. The CSI-RS parameters that may be cycled may include at least one of the following: sequence, CSI-RS resource mapping, antenna port, orthogonal cover code, etc.

[0095] 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 with four possible seeds to generate the sequence. The seeds may be cycled every four transmissions. The WTRU may be able to determine if up to three consecutive CSI-RS resources have not been transmitted (e.g., due to channel acquisition failure).

[0096] Reference Figure 3 The above-mentioned implicit indication is further described. Figure 3 FIG. 4 shows that the WTRU determines whether there is a previous CSI-RS based on the sequence of the currently received CSI-RS. Figure 3 As shown, at 301, the WTRU receives CSI-RS in each configured opportunity, 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. The WTRU may then receive CSI-RS with sequence 2 in time slot 3m. This may indicate to the WTRU that there is indeed no transmitted CSI-RS in time slots m and 2m. This may also be used by the WTRU to determine the reference time slot for future CSI feedback reporting. At 303, the WTRU does not detect CSI-RS in time slot m or time slot 2m. The WTRU may then 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 using sequence 2) in time slot m or time slot 2m. It should be understood that Figure 3 The above examples of 4 sequences for CSI-RS transmission shown in are not intended to be exclusive or to limit the present application. Any other sequences may be used as long as they may help to implement the principles of the present application.

[0097] In an embodiment, the WTRU may not be able to determine which time slot has the undetected CSI-RS and may not be able to use that information to determine appropriate measurements based on the previously assumed non-transmitted CSI-RS. In other embodiments, the parameters of the CSI-RS may be modified to enable the WTRU to determine the specific time slots where the CSI-RS is missing. For example, the sequence of subsequent CSI-RS may be determined based on whether one or more previous CSI-RS were skipped and the skipped time slots.

[0098] Solutions related to determining the presence of CSI-RS based on WTRU measurements are described below. The WTRU may determine the presence of CSI-RS based on measurements made on a resource where the WTRU expects CSI-RS. For example, the WTRU may perform a signal to interference plus noise ratio (SINR) measurement, and any value below a threshold may cause the WTRU to assume that CSI-RS is not transmitted on the resource. The threshold may be configurable.

[0099] In another embodiment, the WTRU may perform channel acquisition measurements (e.g., clear channel assessment) prior to transmitting the expected CSI-RS resources. The WTRU may determine whether the channel is busy prior to CSI-RS transmission. If the WTRU determines that the channel is busy prior to transmission of the expected CSI-RS resources, it may assume that the CSI-RS resources are not transmitted in this instance. Typically, the above determination may be performed by a processor in the WTRU. In this application, unless otherwise specified, a process performed by a WTRU may generally be performed by its processor.

[0100] The WTRU may assume that a CSI-RS resource is present only if the conditions are 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 one of the other transmissions is present, the WTRU may assume that the CSI-RS resource is also transmitted. For example, the WTRU may be configured with a signal, such as a demodulation reference signal (DMRS), to be transmitted in conjunction with the CSI-RS. If the WTRU successfully detects the associated DMRS, the WTRU may assume that the CSI-RS is also transmitted.

[0101] In an embodiment, the WTRU may only assume the presence of CSI-RS when it is transmitted on resources of an active COT. For example, the WTRU may assume that CSI-RS opportunities occur on LBT subbands of an active COT. Thus, the WTRU may determine the presence of CSI-RS resources based on an indication of a COT structure that may be received prior to the transmission opportunity of the CSI-RS.

[0102] The second embodiment will be described below. The second embodiment relates to increasing the robustness of CSI-RS transmission in the event that CSI-RS is missing due to channel acquisition failure. The improvement in the robustness of CSI-RS transmission can be achieved by increasing the probability of transmitting periodic or semi-persistent CSI-RS. In order to increase the probability of transmitting CSI-RS, the WTRU can be configured to have multiple transmission opportunities bound to a single CSI-RS transmission. In this case, the WTRU may not expect to transmit a single CSI-RS transmission at more than one opportunity. Therefore, in the second embodiment, when it is determined that the CSI-RS resource has indeed been transmitted in the transmission opportunity, the WTRU may not need to continue to monitor other opportunities (i.e., conditional opportunities) bound to the CSI-RS transmission, and when it is determined that the CSI-RS resource has not been transmitted in the transmission opportunity, the WTRU may need to continue to monitor other opportunities bound to the CSI-RS transmission.

[0103] The following will refer to FIG. 4A to FIG. 4B The second embodiment is described in detail. Figure 4A 4 is a flow chart showing a method 400 according to a second embodiment. Figure 4A As shown, the method 400 may include: at 401, obtaining a transmission opportunity of a CSI-RS; at 402, obtaining at least one conditional transmission opportunity of the CSI-RS; and at 403, determining whether to transmit the CSI-RS in the transmission opportunity, wherein if the CSI-RS is not transmitted in the transmission opportunity, at 404, detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities. The above processes 401 to 404 will be described below with reference to specific examples.

[0104] Thus, the WTRU may include a processor. The processor is configured to obtain a transmission opportunity for a channel state information reference signal (CSI-RS); obtain at least one conditional transmission opportunity for the CSI-RS; and determine whether to transmit the CSI-RS in the transmission opportunity. In the event that the CSI-RS is not transmitted in the transmission opportunity, the processor is further configured to detect whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunity.

[0105] like Figure 4AAs shown, at 401, method 400 can include obtaining a transmission opportunity for a CSI-RS.

[0106] The transmission opportunity may be obtained without further processing. In an embodiment, the transmission opportunity may be pre-stored in a memory of the WTRU, and the WTRU may retrieve the transmission opportunity from the memory. In an embodiment, the transmission opportunity may be obtained from the network. In an embodiment, the transmission opportunity may be obtained from a base station or a third party device other than the base station. It should be understood that the above embodiments regarding different sources of transmission opportunities are not intended to be exclusive or limiting of the present application.

[0107] The transmission opportunity may be obtained by additional processing. In an embodiment, the transmission opportunity may 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 may obtain the transmission opportunity.

[0108] For example, at 401, the process of determining a transmission opportunity of a CSI-RS may also include: obtaining a transmission opportunity configuration including a timing offset and a periodicity; and determining the timing of the transmission opportunity based on the timing offset and the periodicity. Thus, the WTRU may be configured to obtain a CSI-RS transmission opportunity configuration including a timing offset and a periodicity, and determine the timing of the transmission opportunity based on the timing offset and the periodicity. In other words, such an offset and periodicity may enable the WTRU to determine the timing of each CSI-RS resource opportunity of the CSI-RS configuration.

[0109] The transmission timing configuration may be obtained in the same or similar manner as the above-mentioned transmission timing. For example, the transmission timing configuration may be obtained from the network, base station, third-party device, or memory of the WTRU. The present application does not limit the source of the configuration as long as the configuration may help implement the principles of the present application.

[0110] The timing offset and periodicity in the transmission opportunity configuration can be used to determine the timing of the transmission opportunity. The timing offset can represent the timing offset value relative to the reference timing (e.g., the reference time slot). The periodicity can represent the length between two consecutive transmission opportunities, that is, how many time slots are within the transmission opportunity periodicity. For example, the value of the timing offset is 0, and the value of the periodicity is m. In this case, the WTRU can determine the transmission opportunity as time slot 0, time slot m, time slot 2m, etc. Therefore, the timing of the transmission opportunity can be obtained. It should be understood that the above-mentioned timing offset and periodicity and their values ​​are given as examples, and they are not intended to be exclusive or limit the present application. The following will refer to Figure 4B The above-mentioned process at 401 is further described.

[0111] 4 , method 400 may include obtaining at least one conditional transmission opportunity for a CSI-RS at 402. That is, the WTRU may obtain one or more conditional transmission opportunities associated with the CSI-RS transmission opportunity obtained at 401.

[0112] At least one conditional transmission opportunity may be obtained without any further processing. At least one conditional transmission opportunity may be obtained in the same or similar manner as the above transmission opportunity. For example, at least one conditional transmission opportunity may be obtained from a network, a base station, a third-party device, or a memory of the WTRU. The present application does not limit the source of the conditional transmission opportunity as long as it helps to implement the principles of the present application.

[0113] At least one conditional transmission opportunity may be obtained by additional processing. In an embodiment, at least one conditional transmission opportunity may 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 may obtain a transmission opportunity.

[0114] For example, at 402, the process of obtaining at least one conditional transmission opportunity of the CSI-RS may also include: obtaining a conditional transmission opportunity configuration including at least one conditional timing value; and determining the at least one conditional transmission opportunity based on the at least one conditional timing value. Therefore, in order to obtain at least one conditional transmission opportunity of the CSI-RS, the processor is further configured to obtain a conditional transmission opportunity configuration including at least one conditional timing value, and determine at least one conditional transmission opportunity based on the at least one conditional timing value.

[0115] The conditional transmission opportunity configuration may indicate one or more conditional timing values ​​associated with the CSI-RS transmission opportunity 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 opportunity). For example, there is a conditional timing value, i.e., 5, in the conditional transmission opportunity configuration, indicating that the conditional transmission opportunity is the 5th time slot after the transmission opportunity obtained at 401. For example, there are two conditional timing values, i.e., 5 and 9, in the conditional transmission opportunity configuration. In this case, there are two conditional transmission opportunities after the transmission opportunity obtained at 401, i.e., the 5th time slot and the 9th time slot. It should be understood that the above examples regarding conditional timing values ​​are given by way of example only, and they are not intended to be exclusive or to limit the present application. Reference will be made below to Figure 4B Conditional transmission opportunities are further described.

[0116] In an embodiment, the conditional transmission opportunity configuration and the above-mentioned transmission opportunity configuration may be combined into a single configuration. That is, the WTRU may obtain a single configuration that includes the transmission opportunity configuration required for the process at 401 and the conditional transmission opportunity configuration required for the process at 402. Thus, the above-mentioned parameters, such as timing offset, periodicity, and conditional timing value, may be included in this single configuration.

[0117] The conditional transmission opportunity is used for transmission of CSI-RS, and it is not used for the condition of CSI-RS transmission for the previously associated timing (e.g., the transmission opportunity obtained at 401, the previous conditional transmission opportunity obtained at 402). In the present application, unless otherwise specified, the terms "transmission opportunity", "CSI-RS transmission opportunity", "CSI-RS transmission" and "CSI-RS opportunity" may be used interchangeably, and the terms "conditional transmission opportunity", "CSI-RS conditional transmission opportunity", "CSI-RS conditional transmission" and "CSI conditional transmission opportunity" may be used interchangeably.

[0118] like Figure 4A As shown, after the processing at 401, the WTRU may determine that the timing offset is 0 and the periodicity is m, and may also determine that the CSI-RS transmission opportunity is configured every m time slots, the first CSI-RS transmission opportunity is time slot 0, and the next CSI-RS transmission opportunity is time slot m. In addition, after the processing at 402, the WTRU may determine that each CSI-RS transmission opportunity is configured with two conditional timing values, namely, 5 and 9. Therefore, the WTRU may determine that the corresponding conditional transmission opportunities relative to time slot 0 are time slot 5 and time slot 9, and the corresponding conditional transmission opportunities relative to time slot m are time slot m+5 and time slot m+9.

[0119] Then, the method 400 may proceed to the process at 403. At 403, the method 400 may include determining whether the CSI-RS is transmitted in the transmission opportunity, wherein if the CSI-RS is not transmitted in the transmission opportunity, detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities at 404. The method 400 may also include, under the condition that the CSI-RS is transmitted in the transmission opportunity (i.e., at 403), not detecting whether the CSI-RS is transmitted in one of the at least one conditional transmission opportunities at 405.

[0120] The WTRU may only need to attempt a CSI-RS in a conditional transmission opportunity if the CSI-RS is not transmitted in (1) the associated fixed transmission opportunity and (2) any previous conditional transmission opportunity associated with the same fixed transmission opportunity. For example, if the WTRU does not detect a 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 need to monitor the CSI-RS transmission in slot 9. In slot m, if the WTRU detects a CSI-RS, it may not need to monitor any associated conditional transmission opportunities in slots m+5 and m+9. If the WTRU detects a CSI-RS in a slot, the WTRU may assume that the resources mapped to the subsequent conditional CSI-RS (e.g., associated with the detected CSI-RS resources) can be reused for transmission of other signals or channels. For example, the RE mapping of a transmission that overlaps with a transmitted conditional CSI-RS may require puncturing (or rate matching) of the resources of the conditional CSI-RS. RE mapping for transmissions that overlap with resources for non-transmitted conditional CSI-RS may not require puncturing (or rate matching) of the resources for the conditional CSI-RS.

[0121] In the second embodiment, the WTRU may detect the CSI-RS in the transmission timing and conditional transmission timing by the method disclosed in the first embodiment described above. For example, the WTRU may determine whether the CSI-RS is transmitted based on an indication of the presence of CSI-RS resources. For another example, the WTRU may determine whether the CSI-RS is transmitted by detecting whether the channel is busy before the transmission timing. Different detection methods for CSI-RS transmission may refer to the first embodiment described above.

[0122] In the example shown in FIG4 , slot 0 is used as the reference slot and thus if the timing offset is 0, the reference slot will be used as the transmission opportunity for the CSI-RS. It should be understood that the reference slot may be any other available slot. Furthermore, when a CSI-RS conditional timing value is configured, the WTRU may use any CSI-RS opportunity or any CSI-RS conditional opportunity associated with the original reference slot bound to the feedback measurement as the reference slot for the feedback measurement.

[0123] In an embodiment, the WTRU may perform measurements on a CSI-RS transmission opportunity, 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 an upcoming associated conditional transmission opportunity. Given that the WTRU may autonomously determine the resources used to feedback the CSI measurements, the WTRU may indicate to the network the resources (original opportunity or conditional opportunity) that it used when providing feedback measurements. This may enable the network to determine whether the WTRU is affected by the hidden mode.

[0124] In an embodiment, the WTRU may be configured with a CSI-RS resource whose transmission timing may depend on another transmission. That is, the transmission timing obtained at 401 may be determined based on another transmission. For example, the WTRU may expect to determine the CSI-RS transmission timing to be determined based on the timing of the associated DMRS transmission or the associated DRS (discovery reference signal) transmission. Considering 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 to limit the present application. The transmission timing 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.

[0125] In an embodiment, the WTRU may be configured with a CSI-RS resource 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 may be determined based on at least one other parameter (e.g., CSI-RS timing, CSI-RS frequency, number of ports for CSI-RS transmission during COT, per-resource block structure of CSI-RS, etc.). The at least one other parameter may include COT timing (e.g., start timing of COT), density of CSI-RS transmission, etc. The at least one other parameter that may be used to determine the timing of CSI-RS transmission will be described below with reference to specific examples.

[0126] For example, the CSI-RS transmission timing may be determined based on the start timing of the COT. In such examples, the CSI-RS resource associated with the CSI-RS transmission timing may be configured with an offset based on the start timing of the COT. The CSI-RS resource may also be configured with a periodicity based on the duration of the COT. Since the start timing of the COT may vary, the CSI-RS transmission timing may also vary. In the present application, unless otherwise specified, the start timing of the COT may also be referred to as the COT timing.

[0127] In some cases, such variable timing may cause CSI-RS transmissions to collide with other transmissions. For example, a variable timing CSI-RS may collide with a non-variable timing CSI-RS, DRS, control resource set (CORESET), or DMRS. In such cases, the WTRU may use the transmission priorities that may be configured to determine 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 the event of a collision, the WTRU may only expect the presence of the CSI-RS with the highest or lowest index value.

[0128] The WTRU may expect all types of CSI-RS to use variable timing. For example, the zero-power (ZP) CSI-RS used for physical downlink shared channel (PDSCH) mapping may also be shifted according to the COT timing and / or duration.

[0129] The WTRU may be configured with an association of a reporting configuration with one or several resource sets indicating a set of downlink resources for which CSI measurements should be performed. However, due to the uncertainty of LBT and the start timing of COT, the network may not shift or switch the CSI-RS transmission 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.

[0130] In an implementation scheme, CSI-RS transmission can 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 opportunity can be configured with a CSI-RS resource mapping corresponding to the density of the CSI resources. That is, the transmission opportunity configuration obtained at 401 can also include a CSI-RS resource mapping corresponding to the density of the CSI resources. The density of the CSI resources can be defined as the number of resource elements per resource block (N). Based on the results of the LBT (e.g., the duration of the COT, the bandwidth obtained, etc.), the base station can reduce the number of ports for a given CSI-RS transmission during the COT. To this end, the CSI-RS configuration can be composed of M aggregation sizes - x i Composition, according to the following equation 1.

[0131]

[0132] Here, M represents the full-size CSI-RS resource configured by RRC. Different aggregation levels can be indexed from 1 to M.

[0133] In an embodiment, the density reduction may be explicit. The WTRU receives the density of CSI resources during the COT in an aperiodic triggered state. The WTRU may also receive a DCI with a dedicated DCI field to activate an aggregation level at the start of the COT.

[0134] In an embodiment, the density reduction may be implicit and the WTRU may be configured with a mapping between aggregation levels and COT durations. For example, the WTRU may initially be configured with a size-x M CSI resources, for COT duration T longer than K slots, are reduced in size to size - when V ≤ T < K. xM-1 , and when W≤T<V the size is reduced to size -xM-2 Etc. This may be used to allow the network to prioritize one type of transmission (eg, PDSCH for demanding WTRUs) over CSI-RS transmissions when the duration of the acquired channel is short.

[0135] Similarly, implicit density reduction may be performed by the WTRU based on the identification of subbands acquired during COT.A similar mapping between the acquired subbands and CSI resource density may be configured to the WTRU.

[0136] In an embodiment, the CSI-RS transmission may be determined based on the density of CSI-RS transmissions. For example, the per-resource block structure outlined above may need to accommodate the COT start timing. For example, if the COT starts in the middle of a slot, the structure may switch to one or more symbols within a given RB where the CSI-RS is transmitted. Thus, the WTRU may maintain the same CSI structure (i.e., same frequency and time, 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 may apply this switch only to the first slot of the COT or further to multiple slots of the COT.

[0137] In case of periodic CSI-RS transmission, the WTRU may assume that the configured CSI-RS transmission occurs once every Nth time slot.

[0138] Similarly, as described above, the WTRU may be configured with a mapping of the COT duration and the time at which CSI-RS transmissions occur. If the COT duration is greater than K slots, the WTRU may expect CSI-RS transmissions with N periodicity (e.g., every Nth slot). If the COT duration is less than K slots, the WTRU may, for example, expect CSI-RS transmissions with NT periodicity (i.e., every NT slots), where T may be a configurable value or may be determined as a function of K. This modification of the timing structure may also be signaled by the network via downlink control information (DCI) when the COT is initiated.

[0139] In an embodiment, the density of CSI-RS transmissions in frequency may be modified. For example, the per-resource block structure outlined above may need to be adjusted based on the results of base station channel acquisition. For example, the CSI-RS may be configured for CSI-RS transmission in every RB corresponding to a density equal to 1, in every two RBs corresponding to a density equal to 1 / 2, and so on. The WTRU may be further configured with a relationship between the amount of bandwidth acquired in an active DL bandwidth part (BWP) and the density of CSI-RS transmissions. For example, if the base station acquires all subbands of the active DL BWP, the WTRU may expect a minimum density of CSI-RS transmissions. While if only a subset of the subbands of the active DL BWP are acquired, the WTRU may expect a higher density of CSI-RS configured within the acquired subbands.

[0140] The WTRU may also anticipate 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 acquired a set of subbands or the WTRU has acquired a set of subbands (i.e., scenario inside the COT), it may apply a first CSI-RS transmission density. If the WTRU or the base station has not yet acquired a set of subbands (i.e., scenario outside the COT), the WTRU may apply a second density scheme.

[0141] The WTRU may be configured with an alternative CSI-RS configuration as an alternative to the resources associated with the reporting configuration of the triggered state that is used by the WTRU only when a set of conditions are met. These conditions may be associated with the transmission of at least one of the following parameters: COT duration, acquired bandwidth, number of previously reported CSI feedbacks, number of untransmitted CSI-RS, 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 may also be associated with any other parameters as long as these conditions help to implement the principles of the present application.

[0142] The configured alternative CSI-RS configuration may, for example, have a higher density in time / frequency. For example, the WTRU may be configured with an n-port CSI-RS with a given density (e.g., a single-port CSI-RS with density 3, corresponding to 3 REs per RB). The WTRU may apply an n-port CSI-RS if the acquired 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.

[0143] In an embodiment, the transmission opportunity configuration may also include a CSI-RS triggering offset. The CSI-RS triggering offset may indicate the number of time slots between the time slot containing the DCI that triggers a set of non-periodic non-zero power (NZP) CSI-RS resources and the time slot in which the CSI-RS resources are transmitted.

[0144] The CSI-RS resource may have been triggered in a DCI within one COT and transmitted in a slot of the next COT. If the network cannot obtain a long enough channel, the WTRU may assume that the CSI-RS will be transmitted at the minimum between the COT duration and the CSI-RS triggering offset.

[0145] In an alternative embodiment, if the CSI-RS transmission time slot exceeds the maximum number of time 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 statically preconfigured RRC pattern, e.g., every odd time slot; or (2) an RRC preconfigured pattern that is a function of different COT durations. For example, for a COT duration from 1 to x time slots, the WTRU may monitor the CSI at a first granularity (e.g., every time slot), for a COT duration from x+1 time slots to n time slots, the WTRU may monitor the CSI at a second granularity (e.g., every odd or even time slot); for a COT duration from n+1 time slots to y time slots, the WTRU may monitor the CSI at a third granularity (e.g., every t time slots), and so on. It should be understood that the above examples of different granularities are merely exemplary and they are not intended to be exclusive or limiting of the present application.

[0146] CSI-RS based measurements are described below. A WTRU operating with multiple LBT subbands may be configured to perform measurements on one or more CSI-RS resources present in multiple subbands. In one approach, the WTRU may expect one or more CSI-RS to be contained within a single LBT subband. In such cases, the WTRU may report feedback for one or more CSI-RS that is included in the LBT subband in which the one or more CSI-RS are transmitted. The WTRU may indicate the set of LBT subbands for which feedback is reported. 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.

[0147] In an alternative embodiment, the CSI-RS may span multiple LBT subbands. In this case, the WTRU may report measurements on a portion of the transmitted CSI-RS. For example, the WTRU may use subband reporting such that each subband measurement corresponds to a portion of the CSI-RS present.

[0148] The WTRU may report wideband CSI feedback covering multiple portions of the CSI-RS present. For example, the WTRU may be configured with CSI-RS spanning many (x) LBT subbands. However, the WTRU may receive CSI-RS only in the first LBT subband and the second LBT subband. The WTRU may determine to report wideband CSI feedback, assuming that the wideband bandwidth is the first LBT subband and the second LBT subband (i.e., all subbands where CSI-RS is received). Wideband feedback is determined only for a set of consecutive LBT subbands. The WTRU may report multiple wideband feedbacks, each for a set of consecutive LBT subbands. The wideband CSI feedback may indicate a set of CSI-RS resources (or LBT subbands) to which the wideband CSI feedback applies.

[0149] Embodiments of cross-COT measurement and reporting are described below. A WTRU may receive CSI-RS resources in a first COT but have only 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 report resource. In this application, the terms "feedback" and "feedback report" may be used interchangeably unless otherwise specified.

[0150] In an embodiment, a WTRU that feedbacks measurements in a 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 group of LBT subbands may have feedback resources only in a second COT consisting of a second group of LBT subbands. The WTRU may report at least one of the following: measurements applicable to LBT subbands of the first COT, measurements applicable to LBT subbands of the second COT, or measurements applicable to a set of LCT subbands applicable to the first COT and the second COT. In such an example, if the CSI-RS received in the first COT is applicable to the first group of LBT subbands, the second group of LBT subbands, and the third group of LBT subbands, but the second COT is valid only in the second group of LBT subbands, the WTRU may report measurements applicable only to the second group of LBT subbands.

[0151] A feedback reporting instance may be bound to a reference slot or subframe. However, in some cases, the CSI-RS in the reference slot may not exist. Therefore, the WTRU may assume that a set of reference slots is bound to each feedback reporting instance.

[0152] In one embodiment, the WTRU may report measurements only for a single CSI-RS opportunity within the set of reference slots. The WTRU may use the earliest or latest reference slot in the set where the CSI-RS is present as the reference slot. In another embodiment, the WTRU may perform measurements on a subset of reference slots within the set of reference slots where the CSI-RS is present. In another embodiment, the WTRU may perform average measurements on a subset of reference slots within the set of reference slots where the CSI-RS is present.

[0153] The WTRU may report feedback even when no CSI-RS is transmitted. This may enable a hidden annotated AN indication 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 measurement applicable to the reference slot (or set of reference slots) associated with the CSI-RS resource.

[0154] In one embodiment, the WTRU may request CSI-RS transmission, for example, if CSI-RS is not present in the reference slot set 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 acquired by the WTRU, in which case the WTRU may indicate the parameters of the COT to the network in order to activate CSI-RS with COT timing dependency.

[0155] 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. In addition, the WTRU may determine the content of the CSI feedback based on parameters associated with the CSI-RS transmission 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 complete CSI feedback report (e.g., including a subband report). 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 wideband values).

[0156] In an alternative embodiment, the content of the CSI feedback report may also depend on the time gap between the COT at which the CSI-RS resources are received and the COT at which the CSI feedback is reported. For example, as the time gap increases, the WTRU may reduce the granularity of the feedback report content.

[0157] In an embodiment, PUCCH resources may be dynamically triggered to transmit CSI feedback.Such dynamically triggered PUCCH resources may enable the WTRU to perform CAT1 or CAT2 PBT before accessing an unlicensed channel.

[0158] In an embodiment, the WTRU may be configured with a set of PUCCH resources. The WTRU may only use a set of PUCCH resources if they are dynamically triggered by the base station. The trigger may indicate to the WTRU a reference timeslot from which feedback report measurements should be obtained. In another solution, the dynamically triggered PUCCH resources may be preconfigured with a reference timeslot (or a set of reference timeslots) from which the CSI measurements are obtained.

[0159] Unless the WTRU can be scheduled in the DL, CSI feedback may not have 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 acquire a new COT just to transmit CSI feedback that may not be useful. If the WTRU has been indicated in the previous COT that more DL data transmissions can be expected, the WTRU may (e.g., only may) acquire a COT for the sole purpose of transmitting CSI feedback. For example, the WTRU may have received transmissions in the first COT and may have performed measurements on the CSI-RS resources that existed 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 a subsequent COT, the WTRU may attempt to acquire a channel before the CSI feedback resources in order to provide relevant CSI feedback information to the base station.

[0160] In an embodiment, the WTRU may obtain the COT and transmit CSI feedback if the WTRU also needs to transmit HARQ feedback for the previous COT. The WTRU may multiplex the CSI feedback with the HARQ feedback. In a variant of the embodiment, the WTRU may multiplex the CSI feedback only if there is at least one negative acknowledgement (NACK) in the HARQ feedback, taking into account that the WTRU may subsequently expect another DL transmission.

[0161] If the WTRU is configured to report multiple CSI feedbacks, including channel quality indicator (CQI), channel resource indicator (CRI), L1 beam measurement results, precoding matrix indicator (PMI), rank indicator (RI), 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 results 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 report only a subset of the configured number of reports. The WTRU may be configured with a priority associated with the report content, which changes based on the changes in the LBT results. For example, CRI may have the highest priority, CQI may have the second priority, L1-RSRP may have the third priority, PMI may have the fourth priority, and so on.

[0162] The WTRU may also report quantities associated with one reporting 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 reporting instances corresponding to the same trigger state.

[0163] 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 a report configuration type and a type of LBT that the WTRU may perform to obtain resources for CSI feedback. For example, if the WTRU is configured with periodic reporting on PUCCH, it may also be configured with a condition that PUCCH is only used when it requires an LBT category of 2 or lower. Although the features and elements are described above in particular combinations, a person of ordinary skill in the art will understand that each feature or element may be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over a wired or wireless connection) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media (such as internal hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor in association with software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

[0164] 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 the present application. The singular forms "a", "the" and "said" may be intended to include multiple elements. The terms "include" and "comprise" are intended to include non-exclusive inclusions. Although the present application is described in detail with reference to the aforementioned embodiments, it should be understood that the aforementioned embodiments may be modified, and such modifications do not depart from the scope of the present 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 opportunities for receiving a channel state information reference signal (CSI-RS) transmission; receiving second information indicating a second set of transmission opportunities for receiving CSI-RS transmissions; as well as In response to determining that a CSI-RS transmission is not received in a first transmission opportunity in the first group of transmission opportunities, receiving a CSI-RS transmission in at least one transmission opportunity in the second group of transmission opportunities, wherein the determination is performed by detecting that a channel associated with the first transmission opportunity in the first group of transmission opportunities is busy immediately before the first transmission opportunity in the first group of transmission opportunities.

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

3. The method of claim 1 , wherein determining whether a first CSI-RS transmission is received in the first transmission opportunity in the first set of transmission opportunities is based on a measurement, based on an indication received from a base station, or based on a parameter of another CSI-RS transmission. 4 . The method of claim 1 , wherein the second information indicating the second set of transmission opportunities for receiving CSI-RS transmissions indicates one or more time offset values ​​from one of the first set of transmission opportunities.

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

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

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

8. The method of claim 7, wherein the information indicative of 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 of claim 8, wherein the feedback associated with the CSI-RS transmission received in the time slot comprises feedback associated with multiple CSI-RS transmissions received in a corresponding plurality of time slots.

10. The method of 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).

11. A wireless transmit / receive unit (WTRU), comprising: processor; and Transceiver; The processor and the transceiver are configured to receive first information indicating a first set of transmission opportunities for receiving a channel state information reference signal (CSI-RS) transmission; The processor and the transceiver are configured to receive second information indicating a second set of transmission opportunities for receiving CSI-RS transmissions; as well as The processor and the transceiver are configured to receive a CSI-RS transmission in at least one transmission opportunity in the second group of transmission opportunities in response to determining that a CSI-RS transmission is not received in a first transmission opportunity in the first group of transmission opportunities, wherein the determination is made by detecting that a channel associated with the first transmission opportunity in the first group of transmission opportunities is busy immediately before the first transmission opportunity in the first group of transmission opportunities.

12. The WTRU of claim 11, wherein the processor and the transceiver are configured to, in response to determining that a CSI-RS transmission is received in a first transmission opportunity in the first set of transmission opportunities, receive another CSI-RS transmission in a second transmission opportunity in the first set of transmission opportunities.

13. The WTRU of claim 11, wherein determining whether a first CSI-RS transmission is received in the first transmission opportunity in the first set of transmission opportunities is based on a measurement, based on an indication received from a base station, or based on a parameter of another CSI-RS transmission.

14. The WTRU of claim 11, wherein the second information indicating the second set of transmission opportunities for receiving CSI-RS transmissions indicates one or more time offset values ​​from one of the first set of transmission opportunities.

15. The WTRU of claim 11, wherein at least one parameter of the first set of transmission opportunities or the second set of transmission opportunities is determined based on a parameter associated with a channel occupancy time (COT).

16. The WTRU of claim 15, wherein the at least one parameter comprises one or more of: time and frequency resources, or number of antenna ports.

17. The WTRU of claim 11, wherein the processor and the transceiver are configured to transmit information indicative of a feedback report, wherein content of the feedback report is based on the timing of the received CSI-RS transmission and the timing of the transmission including the information indicative of the feedback report.

18. The WTRU of claim 17, 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.

19. The WTRU of claim 18, wherein the feedback associated with the CSI-RS transmission received in the time slot comprises feedback associated with a plurality of CSI-RS transmissions received in a corresponding plurality of time slots.

20. The WTRU of claim 18, 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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