Channel state information for spatially correlated channels

Abstract

A wireless transmit / receive unit (WTRU) may be configured to receive a channel state information (CSI) configuration. The CSI configuration may include a mapping of a set of CSI-RS ports to a plurality of sets. The WTRU may receive and / or measure a CSI-RS from a first set of CSI-RS ports and / or from shared CSI-RS ports. The WTRU may determine a component precoding matrix indicator based on the received and / or measured CSI-RS. The WTRU may determine a set of coefficients based on the received and / or measured CSI-RS. The set of coefficients may comprise a co-phasing value or vector, and / or an amplitude scaling value or vector. The WTRU may send a CSI report which includes the component PMI and / or the set of coefficients.

Description

CHANNEL STATE INFORMATION FOR SPATIALLY CORRELATED CHANNELS CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No.63 / 643,015, filed May 6, 2024, the entire contents of which are incorporated herein by reference. BACKGROUND

[0002] Transmitting wireless communications at higher frequencies has both challenges and benefits. The benefits include smaller antenna apertures. For example, at higher frequencies a larger number of antenna elements can be embedded in a given area, due to the smaller antenna aperture.

[0003] Larger numbers of antenna ports yield narrow beams. Narrow beams usually have a smaller angular spread. Angular spread determines how spread out the power of the multipath components are. Beams with larger angular spreads fade at a higher rate as compared to beams with a smaller angular spread. A single multi-path arriving from one direction has an angular spread equal to 0, whereas uniformly blasting power in all directions has the maximum angular spread, equal to 1.

[0004] Since narrow beams typically have smaller angular spreads, the using narrow beams can affect the requirement in terms of separation between the antenna elements, to have sufficiently de-correlated antennas. For example, the correlation length increases as the number of antennas increases. Thus, when a larger number of antennas is used and / or at higher frequencies, a larger spacing between the antenna elements is needed to have sufficiently decorrelated antenna elements. However, sufficiently spacing the antenna elements to satisfy the correlation distance may not be realizable at higher frequencies and / or at systems with a larger number of antennas due to space restriction or device sizes. Therefore, such systems may exhibit spatially correlated channels. SUMMARY

[0005] A wireless transmit / receive unit (WTRU) may be configured for antenna panel partitioning. The WTRU may receive channel state information (CSI) reference signals (RSs) from a subset of the CSI-RS antenna ports. The WTRU may determine component CSI(s) for the different antenna port sets. The WTRU may prioritize component CSI(s) in the event of limited physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH) resources for CSI reporting. The WTRU may determine a full CSI based on component CSI(s). WTRU assistance information for CSI-RS configuration may reduce CSI-RS and / or CSI overhead and / or enhance throughput performance.

[0006] A wireless transmit / receive unit (WTRU) may receive channel state information (CSI) configuration information. The CSI configuration information may include a mapping or otherwise indicate associations for CSI-RS antenna ports. The mapping / indication may associate a plurality of CSI-RS antenna ports with a plurality of CSI-RS ports. The plurality of CSI-RS ports may comprise at least a first set of CSI-RS ports and a second set of CSI-RS ports. The mapping may indicate a set of shared CSI-RS ports. The shared CSI-RS ports may be associated with both the first set of CSI-RS ports and the second set of CSI-RS ports. The first set of CSI-RS ports and / or the second set of CSI-RS ports may each comprise one or more subsets of CSI-RS ports. Each of the subsets may be associated with a polarization (e.g., horizontal polarization, vertical polarization).

[0007] The WTRU may receive and / or measure one or more CSI-RSs from a first set of CSI-RS ports and / or from shared CSI-RS ports. The WTRU may determine a component precoding matrix indicator (PMI) (e.g., for a first subset of the first set of CSI-RS ports) based on the received and / or measured CSI- RSs. The component PMI may comprise a vector of complex coefficients. The WTRU may determine sets of coefficients (e.g., for a second subset of the first set of CSI-RS antenna ports, for a first subset of the second set of CSI-RS antenna ports, and / or for a second subset of the second set of CSI-RS antenna ports) based on the received and / or measured CSI-RS. The set of coefficients may comprise a co-phasing value or vector, and / or an amplitude scaling value or vector. The WTRU may send a CSI report which includes the component PMI and / or the set of coefficients. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG.1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented.

[0009] FIG.1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG.1A according to an embodiment.

[0010] FIG.1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communications system illustrated in FIG.1A according to an embodiment.

[0011] FIG.1D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG.1A according to an embodiment.

[0012] FIG.2A is a diagram illustrating an example of channel state information (CSI)-reference signal (RS) ports mapping.

[0013] FIG.2B is a diagram illustrating examples of CSI-RS transmission, CSI determination, and codebook structure for spatially static channels. DETAILED DESCRIPTION

[0014] FIG.1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 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 DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0015] As shown in FIG.1A, the communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a RAN 104 / 113, a CN 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated 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” and / or a “STA”, may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, 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, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a WTRU. Further, any description herein that is described with reference to a UE may be equally applicable to aWTRU (or vice versa). For example, a WTRU may be configured to perform any of the processes or procedures described herein as being performed by a UE (or vice versa).

[0016] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106 / 115, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0017] The base station 114a may be part of the RAN 104 / 113, which may also include other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or 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 licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one for each sector of the cell. In an 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 desired spatial directions.

[0018] 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).

[0019] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System(UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 115 / 116 / 117 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed UL Packet Access (HSUPA).

[0020] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0021] In an 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 New Radio (NR).

[0022] In an 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 instance using dual connectivity (DC) principles. Thus, the air interface utilized by 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., an eNB and a gNB).

[0023] 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, CDMA20001X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0024] The base station 114b in FIG.1A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, 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 an 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-basedRAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. As shown in FIG.1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106 / 115.

[0025] The RAN 104 / 113 may be in communication with the CN 106 / 115, which may be any type of network configured to provide voice, data, applications, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 / 115 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 shown in FIG.1A, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may be utilizing a NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0026] The CN 106 / 115 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide 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), 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 communications 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 / 113 or a different RAT.

[0027] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG.1A may be configured to communicate with 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.

[0028] FIG.1B is a system diagram illustrating an example WTRU 102. As shown in FIG.1B, the WTRU 102 may include 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, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0029] 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 in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG.1B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0030] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0031] Although the transmit / receive element 122 is depicted in FIG.1B 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.

[0032] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit / receive element 122 and to demodulate the signals that are received by the transmit / receiveelement 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11, for example.

[0033] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and / or the removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0034] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to the 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, and the like.

[0035] 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 over the air interface 116 from a base station (e.g., base stations 114a, 114b) and / or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location- determination method while remaining consistent with an embodiment.

[0036] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequencymodulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a Virtual Reality and / or Augmented Reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors, the sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor; an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, and / or a humidity sensor.

[0037] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and downlink (e.g., for reception) may be concurrent and / or simultaneous. The full duplex radio may include an interference management unit 139 to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., a separate processor (not shown) or via processor 118). In an embodiment, the WRTU 102 may include a half-duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the downlink (e.g., for reception)).

[0038] FIG.1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted 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.

[0039] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-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 eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a.

[0040] Each of the eNode-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, and the like. As shown in FIG.1C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0041] The CN 106 shown in FIG.1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (or PGW) 166. While each of theforegoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0042] The MME 162 may be connected to each of the eNode-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, and the like. 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.

[0043] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter- eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0044] 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.

[0045] 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 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 the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers.

[0046] Although the WTRU is described in FIGS.1A-1D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0047] In representative embodiments, the other network 112 may be a WLAN.

[0048] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have an access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to and / or out ofthe BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. Traffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and / or referred to as peer-to- peer traffic. The peer-to-peer traffic may be sent between (e.g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad- hoc” mode of communication.

[0049] When using the 802.11ac infrastructure mode of operation or a similar mode of operations, 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., 20 MHz wide bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by the STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example in in 802.11 systems. For CSMA / CA, the STAs (e.g., every 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.

[0050] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0051] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, theabove-described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0052] Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. The 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 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support Meter Type Control / Machine- Type Communications, such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and / or limited bandwidths. The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0053] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest 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, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode), transmitting to the AP, the entire available frequency bands may be considered busy even though a majority of the frequency bands remains idle and may be available.

[0054] In the United States, the available frequency bands, which may be used by 802.11ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is 6 MHz to 26 MHz depending on the country code.

[0055] FIG.1D is a system diagram illustrating the RAN 113 and the CN 115 according to an embodiment. As noted above, the RAN 113 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the

[0056] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating 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, gNBs 180a, 108b 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 an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

[0057] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing varying number of OFDM symbols and / or lasting varying lengths of absolute time).

[0058] 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 the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with / connect to gNBs 180a, 180b, 180c while also communicating with / connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serveas a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for servicing WTRUs 102a, 102b, 102c.

[0059] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG.1D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0060] The CN 115 shown in FIG.1D may include at least one AMF 182a, 182b, at least one UPF 184a,184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While each of the foregoing elements are depicted as part of the CN 115, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0061] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N2 interface and may serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different PDU sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of NAS signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for machine type communication (MTC) access, and / or the like. The AMF 162 may provide a control plane function for switching between the RAN 113 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.

[0062] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 115 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 115 via an N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating WTRU IP address, managing PDU sessions, controlling policy enforcement and QoS,providing downlink data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

[0063] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The 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 downlink packets, providing mobility anchoring, and the like.

[0064] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include, or may communicate with, an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to the other networks 112, which may include other wired and / or wireless networks that are owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local Data Network (DN) 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0065] In view of Figures 1A-1D, and the corresponding description of Figures 1A-1D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-ab, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0066] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and / or in an operator network environment. For example, the one or more emulation devices may perform the 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 emulation devices may perform the one or more, or all, functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and / or may performing testing using over-the-air wireless communications.

[0067] The one or more emulation devices may perform the one or more, including all, functions while not being implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communications via RF circuitry (e.g., which may include one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0068] Correlation and / or cross-correlation depend on the spacing between two or more antenna elements. Normally, two antenna elements are considered sufficiently de-correlated when the associated cross-correlation is below 0.4. Cross-correlation of less than 0.4 is a statistical definition of correlation length. In other words, at correlation length, the cross correlation is less than 0.4. Correlation length (^^), the angular spread (^^), and the wavelength (^^) are related through the Equation 1, below. Equation 1 ^^ ൌ^^

[0069] MIMO systems with a large number of antennas may be time and frequency resources hungry in terms of transmission of the reference signals and reporting of the channel information. For example, the channel state information (CSI)-reference signal (RS) (CSI-RS) overhead and the CSI (e.g., CSI RS resource indicator (CRI), rank of the channel, precoding matrix indicator (PMI), channel quality indicator (CQI), etc.) reporting overhead increases as a function of the number of CSI-RS antenna ports. Fortunately, in the embodiments herein, the spatial correlation or correlation among the antenna elements can be exploited to reduce both the resources needed for transmission of the reference signals (e.g., CSI- RS) and the resources needed for reporting of the determined channel information (e.g., CSI) in a larger antenna array system.

[0070] Cellular networks may use various numbers of CSI-RS antenna ports. Some cellular networks can use 2 to 32 ports for CSI-RS. Other examples of networks may use more CSI-RS antenna ports, for example, 128 ports or more. In examples, the WTRU in a cellular network may receive a CSI-RS from each CSI-RS port and determine CSI for all CSI-RS ports.

[0071] Current techniques for CSI determination can be very expensive in terms of the resources needed for transmission of the CSI-RS and reporting of the CSI. The techniques presented herein can help to exploit the spatial correlation in a larger antenna array systems and reduce CSI-RS resource needs.

[0072] In some embodiments, a WTRU may receive a CSI configuration (e.g., CSI configuration information). The CSI configuration (e.g., configuration information) may include indications for one or more of the following. The CSI configuration may include a mapping (e.g., showing associations) of the CSI-RS (e.g., antenna) ports to a plurality of sets (e.g., of CSI-RS ports). For example, the CSI-RS antenna ports can be mapped to (e.g., associated with) a first set of CSI-RS ports and a second set of CSI- RS ports. The CSI configuration may include a mapping of (e.g., an association between) the CSI-RS ports in each of the plurality of sets of CSI-RS ports to respective multiple subsets of CSI-RS ports. For example, the first set of CSI-RS ports can be mapped to a first subset of CSI-RS antenna ports and a second subset of CSI-RS antenna ports. For example, the first set of CSI-RS ports may comprise the first and second subset of CSI-RS ports, as indicated by the mapping. The first subset of CSI-RS antenna ports associated with the first set of CSI-RS ports may include the horizontal polarizations. The second subset of CSI-RS antenna ports associated with the first set of CSI-RS ports may include the vertical polarizations.

[0073] The CSI configuration (e.g., configuration information) may include number(s) and indices of one or more shared CSI-RS ports in (e.g., each of) one or more of the plurality of sets of CSI-RS antenna ports. For example, the CSI configuration may include number and indices of one or more shared CSI-RS ports in each of the first and second sets of CSI-RS ports.

[0074] The WTRU may receive and / or measure a CSI-RS from the first set of CSI-RS ports and / or from the shared CSI-RS ports in each of the other (e.g., other than the first set of CSI-RS ports) set(s) of CSI-RS ports that include shared CSI-RS ports. The WTRU may perform one or more of the following based on the reception and / or measurement of the CSI-RSs.

[0075] The WTRU may determine a first component PMI (e.g., ^^^^^^^), for the first subset of CSI-RS antenna ports associated with the first set of CSI-RS ports. For example, the WTRU may determine a first component PMI (e.g., ^^^^^^^) for the horizontal polarizations of the first set of CSI-RS ports.

[0076] The WTRU may determine at least one of a first set of coefficient(s) (e.g., ^^^), a second set of coefficient(s) (e.g., ^^ଶ), and / or a third set of coefficient(s) (e.g., ^^ଷ). Each set of coefficient(s) may comprise a single co-phasing value or a vector of co-phasing values. Additionally, or alternatively, each set of coefficient(s) may comprise a single amplitude scaling value or a vector of amplitude scaling values.

[0077] The first component PMI combined with (e.g., via a mathematical function) one or more of the first, second and / or third sets of coefficients may indicate (e.g., yield) one or more of a second component PMI (e.g., for the CSI-ports in the first set with vertical polarization), a third component PMI (e.g., for the CSI- ports in the second set with horizontal polarization) and / or a fourth component PMI (e.g., for the CSI-ports in the second set with vertical polarization). For example, the first, second, and / or third sets of coefficients may be used, in combination with the first component PMI, to compute or derive the second, third, and / or fourth component PMIs.

[0078] The WTRU may send a CSI report which includes indications for the first component PMI and / or one or more of the first set of coefficient(s), the second set of coefficient(s), and / or the third set of coefficient(s).

[0079] The WTRU may receive CSI-RS from a set of antenna ports, where the set of antenna port changes over time and / or frequency, with common / shared antenna ports in different antenna sets. The WTRU may determine a CSI for the set of antenna ports and use it to derive a CSI for antenna ports in other sets.

[0080] A WTRU may perform actions and / or steps to: receive CSI-RS from a subset of CSI-RS antenna ports, determine CSI, prioritize CSI for CSI reporting, and / or provide WTRU assistance information for CSI- RS configuration. These actions / and or steps may provide benefits, for example, reducing CSI-RS and CSI overhead.

[0081] CSI-RS Configuration is discussed herein.

[0082] A WTRU may be semi-statically or dynamically configured (e.g., by RRC, MAC-CE and / or DCI) to receive a CSI configuration (e.g., CSI configuration information). The CSI configuration may include one or more of the following.

[0083] The CSI configuration may include a number of CSI-RS antenna ports (e.g., the antenna panel has ^^ number of CSI-RS antenna ports).

[0084] The CSI configuration may include a number of CSI-RS antenna ports on the first dimension of the antenna panel, (e.g., the first dimension of the antenna panel has ^^^number of CSI-RS antenna ports).

[0085] The CSI configuration may include a number of CSI-RS antenna ports on the second dimension of the antenna panel, (e.g., the second dimension of the antenna panel has ^^ଶnumber of CSI-RS antenna ports).

[0086] The CSI configuration may include a Type of CSI-RS antenna ports, (e.g., dual-polarized antenna ports or single polarized antenna ports). For example, the total number of antenna ports per panel may beequal to ^^ ൌ ^^^^^ଶ if the gNB is using single polarized antenna ports and may equal ^^ ൌ 2^^^^^ଶ if thegNB is using dual-polarized antenna ports.

[0087] The CSI configuration may include an indication that the CSI-RS antenna ports are divided, partitioned, or grouped into two or more sets of CSI-RS antenna ports. For example, an indication that the ^^ number of CSI-RS antenna ports are divided into even-numbered CSI-RS antenna ports, termed as the first set of CSI-RS antenna ports and odd-numbered CSI-RS antenna ports, termed as the second set of CSI-RS antenna ports.

[0088] The CSI configuration may include an indication that the first set of antenna ports and / or the second set of antenna ports are divided, partitioned, or grouped into a first subset of antenna ports, a second subset of antenna ports and / or a third set of antenna ports, For example, the first (e.g., or second, or third) set of CSI-RS ports may be mapped to a first subset of CSI-RS ports and a second subset of CSI- RS ports. The first subset of CSI-RS ports associated with the first set of CSI-RS ports may include the horizontal polarizations. The second subset of CSI-RS ports associated with the first set of CSI-RS ports may include the vertical polarizations. The first subset of CSI-RS ports associated with the first set of CSI- RS ports may include the even numbered or odd numbered CSI-RS ports within the first set of CSI-RS antenna ports.

[0089] The CSI configuration may include an indication of a third set of antenna ports, and an association of the third set of antenna ports to the first set of antenna ports and to the second set of antenna ports. For example, the third set of antenna ports may also be termed as shared / common antenna ports. For example, the shared / common ports or third set of antenna ports may be associated with the first and second set of ports. For example, the shared / common ports or third set of antenna ports may be a set of antenna ports that are common or shared ports in the first set of antenna ports and in the second set of antenna ports. For example, the shared / common ports for the first set of antenna ports may be comprised of antenna ports in the second set of antenna ports that are also comprised in the first set of antenna ports.

[0090] The CSI configuration may include an indication of the number of CSI-RS reception occasions for which the first set of antenna ports, the second set of antenna ports, and the third set of antenna ports remains unchanged. For example, the first set of antenna ports, the second set of antenna ports and the third set of antenna ports may remain unchanged for two or more CSI-RS reception occasions or for two or more time-instances of CSI reporting.

[0091] Reference signals are discussed herein.

[0092] A single antenna panel may have a plurality of CSI-RS antenna ports (e.g., ^^ number of CSI-RS antenna ports). The CSI-RS antenna ports may be divided, partitioned, or grouped into two or more sets of CSI-RS antenna ports. For example, the even-numbered CSI-RS antenna ports and / or port-groups may be termed as the first set of CSI-RS antenna ports and the odd-numbered CSI-RS antenna ports and / or port- groups may be termed as the second set of CSI-RS antenna ports. The first set of CSI-RS antenna ports may include ^^^number of CSI-RS antenna ports. The second set of CSI-RS antenna ports may include^^ଶ number of CSI-RS antenna ports. The total CSI-RS antenna ports may equal ^^ ൌ ^^^ ^ ^^ଶ. A thirdCSI-RS antenna ports also termed as shared and / or common CSI-RS antenna ports may include zero or more CSI-RS antenna ports from the first set of CSI-RS antenna ports and / or zero or more CSI-RS antenna ports from the second set of CSI-RS antenna ports. The zero or more CSI-RS antenna ports in the first set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports is denoted by ^^^. The zero or more CSI-RS antenna ports in the second set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports is denoted by ^^ଶ. Each set of CSI-RS antenna ports may include a first subset of CSI-RS ports and a second subset of CSI-RS antenna ports. For example, the first set of CSI-RS ports may include a first subset of CSI-RS ports (e.g., a first polarization antenna port or a horizontal polarization antenna port and a second subset of CSI-RS ports), (e.g., a second polarization antenna port or a vertical polarization antenna port). An example of a single antenna panel with 48 dual-polarized CSI-RS antenna ports, two set of CSI-RS antenna ports with ^^^ ൌ 24, ^^ଶ ൌ 24, ^^^ ൌ 4 and^^ଶ ൌ 4 is provided in FIG.2A.

[0093] In examples, the WTRU may receive a reference signal (e.g., CSI-RS) for CSI measurement from a subset (e.g., only from a subset) of the CSI-RS antenna ports at each of the CSI-RS reception occasions.

[0094] In examples, at the first CSI-RS reception occasion, the WTRU may receive a CSI-RS from the first set of CSI-RS antenna ports having ^^^number of CSI-RS antenna ports and from the CSI-RS antenna ports of the second set of CSI-RSports included in the third set of CSI-RS antenna ports. For example, the WTRU may receive CSI-RS from ^^^^^^ଶnumber of CSI-RS antenna ports, where ^^ଶis the number of CSI-RS antenna ports in the second set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports.

[0095] In examples, at the second CSI-RS reception occasion, the WTRU may receive a CSI-RS from the second set of CSI-RS antenna ports having ^^ଶnumber of CSI-RS antenna ports and / or from the CSI-RS antenna ports of the first set of CSI-RS antenna ports included in the third set of CSI-RS antenna ports. For example, the WTRU may receive CSI-RS from ^^ଶ^^^^number of CSI-RS antenna ports, where ^^^is the number of CSI-RS antenna ports in the first set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports.

[0096] In examples, at the first CSI-RS reception occasion, the WTRU may receive a CSI-RS from the first set of CSI-RS antenna ports having ^^^number of CSI-RS antenna ports, from the CSI-RS antenna ports of the second set of CSI-RS antenna ports included in the fourth set of CSI-RS antenna ports, and / or fromthe CSI-RS antenna ports of the set of CSI-RS antenna ports included in the fourth set of CSI-RS antenna ports. For example, the WTRU may receive CSI-RS from ^^^^^^ଶ^^^ଷnumber of CSI-RS antenna ports, where ^^ଶand ^^ଷare the number of CSI-RS antenna ports in the second and third set of CSI-RS antenna ports that are included in the fourth set of CSI-RS antenna ports, respectively.

[0097] In examples, at the second CSI-RS reception occasion, the WTRU may receive a CSI-RS from the second set of CSI-RS antenna ports having ^^ଶnumber of CSI-RS antenna ports, from the CSI-RS antenna ports of the first set of CSI-RS antenna ports included in the fourth set of CSI-RS antenna ports, and / or from the CSI-RS antenna ports of the third set of CSI-RS antenna ports included in the fourth set of CSI-RS antenna ports. For example, the WTRU may receive CSI-RS from ^^ଶ^^^^^^^ଷnumber of CSI-RS antenna ports, where ^^^and ^^ଷare the number of CSI-RS antenna in the first and third set of CSI-RS antenna portsincluded in the fourth set of CSI-RS antenna ports, respectively.

[0098] In examples, at the third CSI-RS reception occasion, the WTRU may receive a CSI-RS from the third set of CSI-RS antenna ports having ^^ଷnumber of CSI-RS antenna ports, from the CSI-RS antenna ports of the first set of CSI-RS antenna ports included in the fourth set of CSI-RS antenna ports, and / or from the CSI-RS antenna ports of the second set of CSI-RS antenna ports included in the fourth set of CSI- RS antenna ports. For example, the WTRU may receive CSI-RS from ^^ଷ^^^^^^^ଶnumber of CSI-RS antenna ports, where ^^^and ^^ଶare the number of CSI-RS antenna ports in the first and second set of CSI-RS antennaare included in the fourth set of CSI-RS antenna ports, respectively.

[0099] Common / shared CSI-RS ports are discussed herein.

[0100] A WTRU may be configured with one or more (e.g., two) sets of CSI-RS ports, and the WTRU may be configured with indices of ports from the first set that are shared with ports of the second set. The shared set may comprise port indices from the two sets of CSI-RS ports. The WTRU may be configured with or without CSI-RS port sharing.

[0101] If the WTRU receives a configuration without shared CSI-RS ports, the WTRU may determine that the gNB transmits on one antenna port group on the first set of CSI-RS ports, and from a second antenna port group on the second set of CSI-RS ports. Each antenna port group may represent a group ofantennas and may be one of the following: a TRP (e.g., a coresetPoolIndex, CMR group, or TCI); a panel (e.g., TCI); or a polarization.

[0102] The Transmission Configuration Index (TCI) represents a beam / spatial filter which may be associated with a TRP or a panel. The coresetPoolIndex is specified in the case with multiple TRPs with multiple DCIs, and is an index linking a DCI with a TRP. A CSI-RS may be associated (e.g., in the configuration) with a coresetPoolIndex as well. The Channel Measurement Resource (CMR) group is specified as a group of reference signals associated with a TRP. Different TRPs are configured with different CMRs.

[0103] The antennas from one antenna port group may be transmitted from a different set of physical antennas from the antennas in a different antenna port group. For example, the antennas in one antenna port group may be associated with a first TRP, panel, or polarization, and the antennas in a second antenna port group may be associated with a second TRP, panel, or polarization. For example, if the network supports Coherent Joint Transmission (CJT) where the antenna ports are distributed over different TRPs, each antenna port group may correspond to one TRP. Therefore, if sharing is not configured, the two CSI-RS sets may be independent from each other. They may be received at the same time on orthogonal resources in frequency (e.g., FDM), in time (e.g., TDM), and / or in code-domain (e.g., CDM).

[0104] If the WTRU receives a configuration with shared CSI-RS ports, the WTRU may determine a third set of CSI-RS ports (e.g., the shared ports) which are associated with the CSI-RS ports from the first two CSI-RS sets (e.g., antenna port groups). The shared CSI-RS ports may be configured through RRC, where the WTRU receives an explicit configuration to link the index of CSI-RS ports from two CSI-RS sets. For example, the WTRU may receive a bitmap which indicates the index of ports from a first and second CMR that are configured as shared.

[0105] Additionally, or alternatively, the shared ports may be implicitly derived by the WTRU. For example, shared ports may comprise CSI-RS ports associated with different coresetPoolIndex, different panels, different TRPs, and / or different CMRs. For example, if the WTRU is configured for CJT with 2 TRPs, the WTRU may assume that a first set of CSI-RS with one CMR, a second set of CSI-RS with another CMR, and / or the set of shared CSI-RS ports include(s) ports from the first and second CMR. If a different set of TRPs is activated / deactivated, the WTRU may implicitly determine the set of shared CSI-RS ports from the newly activated / deactivated set of TRPs. Additionally, or alternatively, the WTRU may receive a MAC-CE which configures / activates / deactivates the link between indices of two CSI-RS sets(e.g., if the network requires changing the shared ports or activating / deactivating one or more shared ports).

[0106] Alternatively, or additionally, the WTRU may be configured with a time-based pattern which dynamically associates the link between indices of two CSI-RS sets as a function of time (e.g., symbol, slot, frame index). For example, the WTRU may be configured with a randomized pattern which may be WTRU- specific (e.g., scrambled / initialized with the C-RNTI), cell-specific (e.g., scrambled / initialized with the cell ID), and / or RRC configured (e.g., scrambled / initialized with a preconfigured identity / number). One or more set(s) of shared CSI-RS ports may be configured (e.g., S1 and S2). The WTRU may determine the association between one set of shared CSI-RS ports with time (e.g., symbol, slot, frame index) as a function of the randomized pattern. For example, the WTRU may determine that the first shared set, S1, is associated with frame 1, and S2 is associated with frame 2. The pattern may be configured to reset periodically (e.g., every R frames). The WTRU may also determine different port sharing sets associated to different RBs according to a hopping pattern in frequency. For example, in frame 1, the first RB may be associated with the shared set S1, and the second RB may be associated with the shared set S2. In frame 2, the first RB may be associated with the shared set S2, and the second RB may be associated with the shared set S1.

[0107] Channel estimation is discussed herein.

[0108] Herein, a reference signal (RS) may interchangeably be used with a CSI-RS, a demodulation RS (DMRS), signal synchronization block (SSB), sounding RS (SRS), and tracking RS (TRS).

[0109] The WTRU may receive RS from (e.g., only from) a subset of the antenna ports. The channel matrix across the RS antenna ports (e.g., CSI-RS antenna ports) and the receive antenna ports, (e.g., SRS ports) may be denoted as ^^, where ^^ has ^^^number of rows and ^^௧number of columns, where ^^^is the number of receive antenna ports or the number of SRS ports and ^^௧is the number of transmit antennaports or CSI-RS antenna ports. Such a channel matrix is termed as a first channel vector when ^^^ ൌ 1 ora first channel matrix when ^^^ ^ 1. To determine the rank of the first channel vector or the first channelmatrix, the WTRU may require knowledge of the first channel vector or first channel matrix (e.g., ^^). However, a CSI-RS reception occasion may correspond to the reception of CSI-RS from a subset of CSI- RS antenna ports (e.g., from ^^^^^^ଶnumber of CSI-RS antenna ports or from ^^ଶ^^^^number ofantenna ports). The WTRU therefore may know (e.g., only know) a channelas ^^^ whichhas a dimension of ^^^number of rows and ^^^^^^ଶor ^^ଶ^^^^number of columns. This channelmatrix may be termed as the second1 or the second channel matrix when^^^ ^ 1. The rank of the second channel matrix, e.g., rank(^^^ ) may therefore not be an accurate rankrepresentation of the first channel matrix (e.g., ^^). To determine the rank of the first channel matrix, the WTRU may first need to make an estimation of the first channel matrix (e.g., an estimation of ^^ from thesecond channel matrix, ^^^ ). The second channel matrix (e.g., ^^^ ) combined with one or more predictionparameters may yield an estimate of the third channel vector or channel matrix. The third channel vector orchannel matrix denoted as ^^^ may be the channel vector or channel matrix associated with the second setof CSI-RS antenna ports at CSI-RS reception occasion ^^, if the first set of CSI-RS antenna ports and the second CSI-RS ports that are included in the third set of CSI-RS ports are used for transmission of the CSI- RS associated with the CSI-RS reception occasion ^^. Different models may be used to determine anestimate of ^^^ from ^^^ . For example, in a linear prediction model, the prediction parameters may include afirst prediction parameter, (e.g., ^^) and a second parameter, (e.g., ^^) and where the prediction on the third channel vector or third channel matrix may be obtained as shown in Equation 2, below: Equation 2 ^^^ ൌ ^^ ^ ^^^^^

[0110] the parameters ^^ and ^^ of Equation 2 can be obtained from the standard deviation of the channelvariables in the channel matrix denoted as ^^^^^ for the channel variable(s) in the channel matrix ^^^ anddenoted as ^^ு^ for the channelthe channel matrix ^^^ , and / or from the mean values of therandom variable of the channel matrix (e.g., the mean value of the random variables of ^^^ denotedmean(^^^ ) and the mean value of the random variables of ^^^ denoted by mean(^^^ )). For the consideredlinear prediction model, the parameter ^^ may be determined according to Equation 3. Equation 3 ^^ ൌ ^^^^^^^^൫^^^ ൯ െ ൫^^^^^൯

[0111] In Equation 3, ^^ ൌ ^^ௌ^^^,Next, the determination of the ಹ^correlation-coefficient is

[0112] Spatial correlation coefficients are discussed herein.

[0113] In solutions, at a given CSI-RS reception occasion, the WTRU may determine a measure of the spatial correlation-coefficient among the CSI-RS antenna ports based on the received CSI-RS (e.g., based on the received CSI-RS from ^^^^^^ଶCSI-RS antenna ports and / or based on the received CSI-RS from ^^ଶ^^^^CSI-RS antenna ports).

[0114] For example, the spatial correlation among two CSI-RS antenna ports, e.g., ^^^^^^^^^and ^^^^^^^^^atCSI-RS reception occasion ^^, denoted as ^^^^^, ^^, ^^^ may be expressed as in Equation 4.Equation 4 ∑ ீି^ ^ୀ^^ℎ^^^^, portୟ^ െ mean൫h^t, portୟ^൯^ ∗ ^ℎ^^^^, portୠ^ െ mean൫h^t, portୠ^൯^^^^^^, ^^, ^^^ ൌଶ portୟ^ െ mean൫h^t, portୟ^ portୠ^ െ^^^, port_a^ is the channel gain reception occasion ^^,port_a^൯ is the mean value of gain at CSI-RS reception occasion ^^across all ^^ subcarriers. For example, mean൫h^t, port_a^൯ ൌ ^ீ∑ீି^ ^ୀ^ ℎ^^^^, port_a^. Based on spatialcorrelation, ^^ may be given as ^^ ൌ ^^^^^,^^, ^^^ௌ^^^ௌ^. ಹ

[0116] In solutions, the WTRU quantized variant of the spatial correlation coefficient.

[0117] In solutions, the WTRU may spatial correlation coefficient coarsely or with a smaller granularity at higher values of the spatial correlation coefficient values and densely or with a higher granularity at smaller values of the spatial correlation coefficient values. For example, the spatial correlation coefficient may take a value in the range -1 and 1. Values of the spatial correlation coefficient can be quantized densely around 1 and -1 and coarsely around 0. For example, the difference between two quantized spatial correlation coefficients around -1 and 1 may be 0.01 and the difference between two quantized spatial correlation coefficients around -0.5 and 0.5 may be 0.1.

[0118] Temporal correlation coefficients are discussed herein.

[0119] A temporal correlation-coefficient among two CSI-RS antenna ports (e.g., ^^^^^^^^^at a first CSI-RS reception occasion ^^^and ^^^^^^^^^at a second CSI-RS reception occasion ^^ଶ), (e.g., denoted by ^^^)denoted as ^^^^^ ,^^, ^^^ may be expressed as according to EquationEquation 5 ^^^^^^, ^^ଶ,^^, ^^^∑ீି^ ^ୀ^^ℎ^^^^^, portୟ^ െ mean൫h^t^, portୟ^൯^ ∗ ^ℎ^^^^ଶ, portୠ^ െ mean൫h^tଶ, portୠ^൯^ଶ ଶ, portୠoccasion ^and at subcarrier ^^ and mean൫h^t , port_a^൯ is the mean value of the channel gain across ^^^^^^^^CSI-RS reception occasion ^^^ across all ^^ subcarriers, (e.g., mean൫h^t୧, port_a^൯ ൌ^ ீ∑ீି^ ^ୀ^ ℎ^^^^^ , port_a^ , where ^^ ൌ 1, 2). Based on spatial correlation, ^^ may be given as ^^ ൌmay receive a reference signal, a measurement signal or a pilot signal at two or moreoccasions from the same CSI-RS antenna port at both CSI-RS reception occasions or from different CSI-RS antenna ports at both CSI-RS reception occasions at the same frequency domain resources, (e.g., at the same sub-carrier(s), or at the same resource element(s) or at the sub-band(s) or at different frequency domain resources).

[0122] In solutions, the WTRU may determine a measure of the temporal correlation-coefficient among the CSI-RS antenna ports based on CSI-RS received at two or more CSI-RS reception occasions, (e.g., based on CSI-RS received CSI-RS at a first CSI-RS reception occasion and based on the received CSI-RS at a second CSI-RS reception occasion).

[0123] For example, at a first CSI-RS reception occasion, the WTRU may receive CSI-RS from a first set of CSI-RS antenna ports and from the CSI-RS antenna ports of the second set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports. At a second CSI-RS reception occasion, the WTRU may receive CSI-RS from a second set of CSI-RS antenna ports and from the CSI-RS antenna ports of the first set of CSI-RS antenna ports that are included in the third set of CSI-RS antenna ports.

[0124] For example, at a first CSI-RS reception occasion, the WTRU may receive CSI-RS from ^^^^^^ଶCSI-RS antenna ports. At a second CSI-RS reception occasion, the WTRU may receive CSI-RS from ^^ଶ^^^^CSI-RS antenna ports.

[0125] In solutions, the temporal correlation-coefficient may be determined based on at least one of the following.

[0126] The temporal correlation-coefficient may be determined based on the same CSI-RS antenna port. In examples, the WTRU may receive a CSI-RS from ^^^^^^^^^at the first CSI-RS reception occasion and receive CSI-RS from ^^^^^^^^^at the second CSI-RS reception occasion. The WTRU may determine a temporal correlation-coefficient based on the CSI-RS received at the first CSI-RS reception occasion from ^^^^^^^^^and / or based on the CSI-RS received at the second CSI-RS reception occasion from ^^^^^^^^^.

[0127] The temporal correlation-coefficient may be determined based on different CSI-RS antenna ports. For example, the WTRU may receive a CSI-RS from ^^^^^^^^^at the first CSI-RS reception occasion and receive CSI-RS from ^^^^^^^^^at the second CSI-RS reception occasion. The WTRU may determinetemporal correlation-coefficient based on the CSI-RS received at the first CSI-RS reception occasion from ^^^^^^^^^and / or based on the CSI-RS received at the second CSI-RS reception occasion from ^^^^^^^^^.

[0128] In solutions, the WTRU may receive a semi-static or dynamic (e.g., by RRC, MAC-CE, and / or DCI) configuration or indication of the port indices to use for determination of the temporal correlation-coefficient.

[0129] For example, the WTRU may receive a dynamic indication to use ^^^^^^^^^at CSI-RS reception occasion ^^^and ^^^^^^^^^at CSI-RS reception occasion ^^ଶfor determination of the temporal correlation- coefficient.

[0130] In solutions, the WTRU may receive a semi-static or dynamic (e.g., by RRC, MAC-CE, and / or DCI) time-domain channel properties (TDCP) report configuration for determination of the temporal correlation- coefficient.

[0131] In solutions, the WTRU may determine TDCP and assume the determined TDCP value as a measure of the temporal correlation-coefficient. The WTRU may combine the determined TDCP with thefirst channel vector or channel matrix, (e.g., denoted by ^^^ ) to predict or estimate the third channel vectoror the third channel matrix, (e.g., the channel matrix denoted by ^^^ ).

[0132] In solutions, the WTRU may determine a quantized variant of the spatial correlation coefficient.

[0133] In solutions, the WTRU may quantize the spatial correlation coefficient coarsely or with a smaller granularity at higher values of the spatial correlation coefficient values and densely or with a higher granularity at smaller values of the spatial correlation coefficient values. For example, the spatial correlation coefficient may take a value in the range -1 and 1. Values of the spatial correlation coefficient can be quantized densely around 1 and -1 and coarsely around 0. For example, the difference between two quantized spatial correlation coefficients around -1 and 1 may be 0.01 and the difference between two quantized spatial correlation coefficients around -0.5 and 0.5 may be 0.1.

[0134] Joint spatial and temporal correlation-coefficients are discussed herein.

[0135] The WTRU may receive a semi-static or dynamic configuration (e.g., by RRC, MAC-CE, and / or DCI) for a RS (e.g., a CSI-RS, an SSB, a DMRS, a tracking reference signal (TRS)), wherein the configuration may include one or more of the following.

[0136] The configuration may include a number of ports used for the transmission of the RS. For example, two ports are used for transmission of the RS from the gNB.

[0137] The configuration may include one or more indices of ports used for transmission of the RS. For example, ^^^^^^^^^and ^^^^^^^^^may be used for transmission of the RS.

[0138] The configuration may include one or more frequency domain resource indices (e.g., subcarrier indices, resource element indices or sub-band indices at which the RSs are being transmitted at each of the transmission occasions). For example, the RS at a first CSI-RS reception occasion (e.g., at CSI-RS reception occasion ^^^), may be transmitted from a first set of CSI-RS port(s) (e.g., ^^^^^^^^^, and at a first set of subcarrier(s) including a subcarrier with index ^^^). In such a case, the RS at a second CSI-RS reception occasion (e.g., at CSI-RS reception occasion ^^ଶ) may be transmitted from a second set of CSI-RS port(s), (e.g., from ^^^^^^^^^at a second subcarrier with index ^^ଶ).

[0139] The WTRU may receive the RS at one or more RS reception occasions from two or more RS antenna ports and determine a measure of the joint spatial and temporal correlation-coefficient. For example, the joint spatial and temporal correlation-coefficient between two antenna ports, (e.g., a first antenna port denoted as ^^^^^^^^^and a second antenna port denoted as ^^^^^^^^^at two RS reception occasions),at two reception occasions (e.g., a first RS reception occasion denoted as ^^^and a second RSreception occasion denoted as ^^ଶ), denoted as ^^^^^^, ^^ଶ, ^^, ^^^ may be determinedto Equation 6.Equation 6 ∑ ீି^^^^ ^^^^^^^, ^^ଶ, ^^, ^^^ ൌ^ୀ^^ ∗ ^^ଶ

[0140] In Equation 6, ^^^, ^^ଶ, ^^^^^^ ൌportୟ^ െ mean^h^^ ∗ ^ℎ^^^^^, portୠ^ െ mean^h^^ଶ ଶ

[0141] The^^^, ^^^ at CSI-RS reception occasion ^^^ where ^^ ∈ ^1,2^ and at subcarrier ^^ and where mean^h^ is the mean value ofthe channel gain across all ports and across all reception occasions ^^^and across all ^^ subcarriers, (e.g.,mean^h^ ൌ ^ ∑்ି^ᇲ௧ᇲୀ^ ∑ ே ି^^ୀ^∑ீି^ ^ୀ^ℎ^^^^௧ᇲ , ^^^^^^^^^^).reception occasions. ^^ᇱmay denote the total number of RS antenna ports used for transmission of the RS at a single RS reception occasion or ^^ᇱmay denote the total number of RS antenna ports considered for determination of the joint spatial and temporalcorrelation-coefficient. ^^ is the total number of subcarriers used for transmission of the RS at each RS occasion.

[0143] In solutions, the joint spatial and temporal correlation-coefficient may be combined with other channel parameters, (e.g., the standard deviation of the random variables of the first and third channelmatrix) to determine a prediction parameter, (e.g., ^^ as ^^ ൌ ^^^^^^, ^^ଶ,^^, ^^^ௌ^^^ௌಹ^).

[0144] The rank of a channel is discussed herein.

[0145] The spatial correlation-coefficient, temporal correlation coefficient, and / or joint spatial and temporalcorrelation coefficients may be used as a prediction parameter to predict the third channel matrix ^^^ or thesecond channel matrix ^^^ . The WTRU then may determine the rank of the first channel matrix, the rank ofthe second channel matrix and / or the rank of the third channel matrix.

[0146] In solutions, the WTRU may determine a CSI parameter (e.g., rank indicator (RI), precoding matrix indicator (PMI), wideband channel quality indicator (CQI), and / or sub-band CQI) upon reception of a RS. For example, the WTRU may determine a CSI parameter upon reception of a first CSI-RS occasion and based on one or more of the following.

[0147] The WTRU may determine a CSI parameter based on the first channel matrix, (e.g., ^^^ ofdimension ^^^ ൈ 2^^^^ ^ ^^ଶ^, where the RS is received from the first set of RS antenna ports and theshared / common ports and ^^^ of dimension ^^^ ൈ 2^^^ଶ ^ ^^^^, where the RS is received from the secondset of RS antenna ports and the shared / common ports).

[0148] The WTRU may determine a CSI parameter based on the second estimated channel matrix, (e.g.,^^ of dimension ^^^ ൈ 2^^^^^ଶ where 2^^^^^ଶ is the total number RS antenna ports and where total numberof first polarization antenna ports are ^^^^^ଶand the total number of second polarization antenna ports are ^^^^^ଶ^.

[0149] The WTRU may determine a CSI parameter based on the third estimated channel matrix, (e.g., ^^^of dimension ^^^ ൈ ^2^^^^^ଶ െ 2^^^^ ^ ^^ଶ^^, where the RS is received from the first set of RS antennaports and the shared / commonand ^^^ of dimension ^^^ ൈ ^2^^^^^ଶ െ 2^^^ଶ ^ ^^^^^, where the RSis received from the second set of RS antenna ports and the share / common ports).

[0150] In solutions, the WTRU may determine and report a first rank value, a second rank value and / or a third rank value. The first rank value may be the rank value of the first channel matrix. The second rank value may be the rank value of the second channel matrix. The third rank value may be the rank value of the third channel matrix.

[0151] In examples, the rank of the first channel matrix may equal ^^^^^^^^൫^^^൯ ൌ min ^^^^ ^ ^^ଶ,^^^^. Ifthe RS is transmitted using the first set of RS antenna ports and ^^^^^^^^൫^^^൯ ൌ min ^^^ଶ ^ ^^^, ^^^^ whenthe RS is transmitted using the second set of RS antenna ports. In the rank of the first channelmatrix may equal ^^^^^^^^൫^^^൯ ൌ min ^^^ᇱ, ^^ ^, where ^^ᇱ is t௧^ ௧ he of RS antenna ports in the first orsecond set of RS antenna ports, e.g., ^^ᇱ ᇱ௧ ൌ ^^^ ^ ^^ଶ or ^^௧ ൌ ^^ଶ ^ ^^^.

[0152] In examples, the rank of the second ^^^^^^^^^^^^ ൌ min ^^^௧ , ^^^^, where ^^௧is the number of RS antenna ports and equalusing dual-polarized antennas.

[0153] In examples, the rank of the third channel matrix equal rank(^^^ ^ ൌ ^^^^^^^^^^ , 2^^^^^ଶ െ 2^^^^ ^^^ଶ^^ when the RS is received from the first set of RS antenna ports and the shared / common ports andrank(^^^ ൌ ^^^^^^^^^^ , ^2^^^^^^ଶ െ 2^^^ଶ ^ ^^^^ ^ when the RS is received from the second set of RSantenna ports and the share / common

[0154] In solutions, the WTRU may report rank of the first channel with a higher priority as compared to the rank of the second and / or third channel matrix.

[0155] In examples, when the available uplink time and frequency resources are limited, the WTRU may drop the rank value of the second and third channel matrix and report the rank value of the first channel matrix.

[0156] CSI determination is discussed herein.

[0157] Precoding Matrix Indicators (PMIs) are discussed herein.

[0158] In solutions, the WTRU may receive a semi-static or dynamic (e.g., by RRC, MAC-CE, and / or DCI) configuration of a codebook of PMIs and / or a vector of a first co-phasing, second co-phasing and / or third co-phasing for determination of a PMI. The codebook and co-phasing maybe jointly or separately configured. One or more of the following may apply.

[0159] When the RS is received from ^^^^^^ଶRS antenna ports, the codebook of PMIs may have^^^^ ^ ^^ଶ^^^^^^ଶ number of PMIs. Alternatively, or additionally, when the RS is received from ^^^ ^ ^^ଶRS antenna ports, the codebook of PMIs may have ^^^^^^^^ଶnumber of PMIs.

[0160] When the RS is received from ^^ଶ^^^^RS antenna ports, the codebook of PMIs may have ^^^ଶ^^^^^^^^^^ଶnumber of PMIs. Alternatively, or additionally, when the RS is received from ^^ଶ^^^^RS antenna ports, the codebook of PMIs may have ^^ଶ^^^^^ଶnumber of PMIs.

[0161] When the RS is received from ^^^^^^ଶRS antenna ports or ^^ଶ^^^^antenna ports and ^^ଶൌ^^^, and / or ^^^ ൌ ^^ଶ, the WTRU may use the same codebook for PMI determination at both RS receptionoccasions.

[0162] When the RS is received from ^^^^^^ଶRS antenna ports or ^^ଶ^^^^antenna ports and ^^ଶ്^^^, and / or ^^^ ് ^^ଶ, the WTRU may use different codebooks at different RS reception occasions.

[0163] Each PMI may be a vector of complex coefficients.

[0164] Each PMI may have ^^^^^^ଶor ^^ଶ^^^^number of complex coefficients.

[0165] For example, each PMI may have ^^^or ^^ଶnumber of complex coefficients.

[0166] The PMI may be for (e.g., only for) the first subset or for the second subset of antenna ports in a first set of antenna ports.

[0167] The PMI may be for (e.g., only for) the first subset or for the second subset of antenna ports in a second set of antenna ports.

[0168] The first co-phasing may be used to determine a PMI for the first subset of antenna ports in a second set of antenna ports, based on the PMI determined for the first subset of antenna ports in the first set of antenna ports.

[0169] For example, the WTRU may determine a PMI, (e.g., a first component PMI denoted as PMI^for the first subset of antenna ports in a first set of antenna ports). The WTRU may determine a PMI for the first subset of antenna ports in a second set of antenna ports, (e.g., denoted as PMIଶbased on ^^^^^^^and the first co-phasing value).

[0170] For example, the PMI for the first subset of antenna ports in the second set of antenna ports maybe determined as ^^^^^^ଶ ൌ ^^^ ^^^^^^^, where ^^^ is the first co-phasing value.

[0171] The second co-phasing may be used to determine a PMI for the second subset of antenna ports in a first set of antenna ports, based on the PMI determined for the first subset of antenna ports in the first set of antenna ports. For example, the WTRU may determine a PMI, (e.g., a first component PMI denoted as PMI^) for the first subset of antenna ports. The WTRU may determine a second co-phasing value (e.g., ^^ଶ) and combine it with ^^^^^^^to determine a PMI for the second subset of antenna ports in the first set of antenna ports. For example, the PMI for the second subset of antenna ports in the first set of antennaports may be determined as ^^^^^^ଷ ൌ ^^ଶ ^^^^^^^.

[0172] The third co-phasing may be used to determine a PMI for the second subset of antenna ports in the second set of antenna ports, based on the PMI determined for the first subset of antenna ports in the first set of antenna ports and / or based on the first and second co-phasing values.

[0173] For example, the WTRU may determine a PMI, (e.g., a first component PMI denoted as PMI^) for the first subset of antenna ports in the first set of antenna ports. The WTRU may determine a first, second and / or a third co-phasing value (e.g., ^^^,^^ଶ, and ^^ଷ) and combine it with ^^^^^^^to determine a PMI for the second subset of antenna ports in the second set of antenna ports. For example, the PMI for the second subset of antenna ports in the second set of antenna ports is determined as ^^^^^^ସൌ ^^^^^ଶ^^ଷ^^^^^^^.

[0174] The PMI for all ports and a single layer may be expressed as ^^^^^^ ൌ ^^^^^^^^, ^^^^^^ଶ, ^^^^^^ଷ,^^^^^^ସ^். ^^^^^^^is for the first subset of antenna ports in a first set of antenna ports and may also be termed as the first component PMI. ^^^^^^ଶis for the second subset of antenna ports in a first set of antenna ports and may also be termed as the second component PMI. ^^^^^^ଷis for the first subset of antenna ports in a second set of antenna ports and may also be termed as the third component PMI. ^^^^^^ସis for the second subset of antenna ports in a second set of antenna ports and may also be termed as the fourth component PMI.

[0175] After an RS reception occasion, (e.g., upon reception of the first RS occasion from the first set of antenna ports), (e.g., ^^^antenna ports and from second set of antenna ports that are included in the first set of antenna portsis also termed as the shared / common antenna port), (e.g., ^^ଶnumber of antenna ports), the WTRU may determine a first PMI, a second PMI and / or a third PMI.

[0176] Herein, a PMI that is determined for the first set of antenna ports and / or for the shared / common antenna ports may be termed as the first PMI. A PMI that is determined for the second set of antenna ports and / or for the shared / common antenna ports may be termed as the second PMI. A PMI that is determined for the all the antenna ports, (e.g., for the first set of antenna ports and for the second set of antenna ports) may be termed as the third PMI.

[0177] The first set of co-phasing may correspond to a vector of co-phasing values or a single co-phasing value. For example, the first set of co-phasing values may include ^^ number of vectors or single valueswith ^^ ൌ 0,⋯ , ^^ െ 1 being the index of each vector or value. The second set co-phasing maycorrespond to a vector of co-phasing values or a single co-phasing value. For example, the second set ofco-phasing values may include ^^ number of vectors or single values with ^^ ൌ 0,⋯ ,^^ െ 1 being theindex of each vector or value. The third set co-phasing may correspond to aco-phasing values or a single co-phasing value. For example, the third set of co-phasing values may include ^^ number ofvectors or single values with ^^ ൌ 0,⋯ , ^^ െ 1 being the index of each vector or value. The codebook ofPMIs may have a plurality of PMIs and the index of each PMI in the codebook of PMI may be denoted by ^^,where ^^ ൌ 0,⋯ , ^^ െ 1.

[0178] Determination of a first PMI is discussed herein.

[0179] In solutions, the WTRU may determine a first PMI by determining the index of a PMI from the codebook of PMIs, (e.g., the index ^^ of a PMI and by determining the index of a co-phasing value), (e.g., the index ^^ from a second set of co-phasing values), based on the first channel matrix.

[0180] In examples, the WTRU may jointly determine ^^ and ^^ by solving the Equation 7. Equation 7 First PMI ൌ∀m୰,a୫x ^^ ^^^^^^^^^^^^^

[0181] In Equation 7, ^^^^^^^^^^^^ is channel when using a firstcomponent PMI with an index ^^ and a co- an index ^^.

[0182] In examples, the WTRU may jointly determine ^^ and ^^ by solving the Equation 8. Equation 8 First PMI ൌ ^∀m୰,a୫x ^^^^^^^^ ^^^^^^^^^^^^

[0183] In Equation 8, ^^^^^^^^^^^^^^^^^^ is the signal to interference and noise ratio (SINR) of the first channel when using a PMI with an index ^^ and a second co-phasing value with an index ^^.

[0184] In examples, the WTRU may jointly determine ^^ and ^^ by solving the Equation 9. Equation 9 First PMI ൌ ^∀m ^^^^^^^^ ^^^^^^^^^^^^

[0185] In Equation 9,rate performance on a hypothetical downlink transmission on the first channel when using a first component PMI with an index ^^ and a second co-phasing value with an index ^^.

[0186] Determination of a second PM is discussed herein.

[0187] In solutions, the WTRU may determine a second PMI by determining the index of a first component PMI from the codebook of PMIs, (e.g., the index ^^ of a PMI and by determining the index of a co-phasing values), (e.g., the index ^^, the index ^^ and the index ^^ from a first set of co-phasing values), a second set of co-phasing values, and / or a third set of co-phasing values, respectively and based on the second channel matrix ^^.

[0188] In examples, the WTRU may jointly determine ^^ and ^^ by solving Equation 10.Equation 10 Second PMI ൌ∀ ୰m,୯a,୫x,ୠ^^ ^^^^^^൫^^^,^^^, ^^^ ൯^

[0189] In Equation 10, second channel whenusing a PMI with an index ^^ and

[0190] In examples, the WTRU may jointly determine ^^, ^^, ^^ and b by solving Equation 11.Equation 11 Second PMI ൌ∀ ୰m,୯a,୫x,ୠ^^^^^^^^ ^^^^^^൫^^^, ^^^,^^^ ൯^

[0191] In Equation 11, SINRand noise ratio (SINR) ofthe second channel index ^^ and co-phasing values with indices ^^,^^ and ^^.

[0192] In examples, may ^^, ^^,^^, and ^^ by solving Equation 12. Equation 12 Second PMI ൌ∀ ୰m,୯,i୫n,ୠBLER ^^^^^^൫^^^, ^^^,^^^ ൯^

[0193] In Equation 12, BLERon a hypotheticaldownlink transmission on the second channelusing a PMI with an index ^^ and co-phasing values with indices ^^,^^, and ^^.

[0194] Determination of a third PMI is discussed herein.

[0195] In solutions, the WTRU may determine a third PMI by determining the index of a first component PMI from the codebook of PMIs, (e.g., the index ^^ of a first component PMI and by determining the index of a first co-phasing value), (e.g., the index ^^ from a first set of co-phasing values), the index ^^ from a second set of co-phasing values, and the index ^^ from a third set of co-phasing values, and based on the third channel matrix.

[0196] In examples, the WTRU may jointly determine ^^, ^^,^^ and / or ^^ by solving Equation 13. Equation 13 Third PMI ൌ m ^^ ^^^^ ^^^൫^^^, ^^^,^^^൯^

[0197] In Equation 13 ^^ ^^^^the third channel when using afirst component PMI withvalue with indices ^^, ^^ and ^^.

[0198] In examples, the WTRU may jointly determine r, ^^,^^ and / or ^^ by solving Equation 14. Equation 14Third PMI ൌ∀ ୰m,୯a,୫x,ୠ^^^^^^^^ ^^^^ ^^^൫^^^,^^^, ^^^൯^

[0199] In Equation 14, ^^^^^^^^ and noise ratio (SINR) ofthe third channel when using a PMI with an index ^^ and co-phasing values with indices ^^, ^^ and ^^.

[0200] In examples, the WTRU may jointly determine ^^, ^^,^^ and / or ^^ by solving Equation 15. Equation 15 Third PMI ൌ∀ ୰m,୯i,୫n,ୠ^^^^^^^^ ^^^^ ^^^൫^^^, ^^^,^^^൯^

[0201] In Equation 15, BLERerror rate performanceon a hypothetical downlink third channel when using a first component PMI with anindex ^^ and co-phasing an ^^, ^^ and / or ^^.

[0202] PMI for more than one layers is discussed herein.

[0203] The PMI determination solutions, mechanisms, techniques, methods, and / or procedures listed, discussed, and / or demonstrated herein are valid for determining a PMI for a single layer as well as PMI(s) for more than one layers. In examples, one or more of the following may apply when determining a PMI for more than one layers.

[0204] The first component PMI, (e.g., ^^^^^^^for a first layer may freely be determined from the codebook of PMIs). For example, the codebook may have ^^ number of PMIs for PMI selection. The WTRU may choose one or more PMIs out of the ^^ number of PMIs for the first layer.

[0205] The first co-phasing value, the second co-phasing value and / or the third co-phasing value for the PMI, (e.g., the first PMI, the second PMI, and / or the third PMI) for the first layer may freely be determined from the first set of co-phasing values, the second set of co-phasing value and / or the third set of co-phasing values, (e.g., indices ^^,^^, and ^^) may be freely selected out of ^^,^^, and ^^ co-phasing values, respectively.

[0206] The first component PMI, (e.g., ^^^^^^^for a first layer determined from the codebook of PMIs) may also be used as a first component PMI for a second layer. For example, the codebook may have ^^ number of PMIs for PMI selection. The WTRU may choose one or more component PMIs out of the ^^ number of PMIs for the first layer. The WTRU may use the same component PMIs for the first layer as the first component PMIs for the second layer.

[0207] The WTRU may determine one or more PMIs from the codebook of PMIs, (e.g., the WTRU may select or determine 4 out of 32 PMIs in the codebook). The WTRU may determine the one or more PMIsbased on a layer with the highest strength or based on a dominant layer, (e.g., a layer with the highest SINR, a layer with the smallest index, a layer with the highest index). For a second layer, the WTRU may choose a first component PMI out of the set of the determined or selected PMIs.

[0208] The first, second, and / or the third co-phasing values determined for the first layer may also be used for a second layer.

[0209] For example, for a first layer, the first, second, and third co-phasing values may equal ^^^, ^^^, and ^^^. For the second layer, the first, second, and third co-phasing values could be െ^^^, െ^^^, and െ^^^.

[0210] For two layers, a first PMI, a second PMI and / or a third PMI may be expressed according to Equation 16. Equation 16 ^^^^^^^െ^^^^^^ é^^^^^^^^^^^െ^^^^^^^^^^ù ú ú

[0211] The WTRU first, second, and / or thirdPMI may be a PMI for a single layer or more than one layer. In examples, the first PMI for a single layer is denoted as ^^^^^^^^^^^ெூభ. In examples, the first PMI for two layers is denoted as ^^^^^^^^^^^ெூమ. In examples,the first PMI for a L layers is denoted as ^^^^^^^^^^^ெூ^ . In examples, the ^^௧^ PMI with 1,⋯ , ^^௧^ layers isdenoted as ^^^ெூ^, where ^^ ൌ 1,⋯ , ^^ and ^^ ൌ 1, ⋯ , ^^.

[0212] PMI based on the channel and a performance defining metric. In examples, the WTRU may select one first PMI out of two or more of first PMIs, where each of the first PMI is of different layers. In examples, the WTRU may select one first PMI out of ^^^^^^^^^^^ெூభand ^^^^^^^^^^^ெூమ. In examples, the WTRU may select one PMI out of ^^^^^^^^^^^ெூభand ^^^^^^^^^^^^^ெூభ. In examples, the WTRU may select one PMI out of ^^^^^^^^^^^ெூభand ^^^^^^^^^^^^^ெூమ.

[0213] The WTRU may select one out of many PMIs based on the channel and a performance defining metric. In examples, the WTRU may select a global best PMI by solving Equation 17. Equation 17 best PMI ൌ m^^൫^^௭^^௭,^൯

[0214] In Equation 17, ^^௭is the channel^^௭,^and ^^൫^^௭^^௭,^൯ is the Shannon capacity of channel ^^௭when using the ^^௧^precoder of ^^ layers.

[0215] In examples, the WTRU may select a global best PMI by solving Equation 18.Equation 18 best PMI ൌ max^^^^^^^^൫^^ ^^ ൯ ∀ ^,୪௭ ௭,^

[0216] In Equation 18, ^^௭is the ^^௭,^and ^^^^^^^^൫^^௭^^௭,^൯ is theSINR observed on channel ^^௭when

[0217] In examples, the WTRU may select a global best PMI by solving Equation 19. Equation 19 best PMI ൌ max^^^^^^^^൫^^ ^^ ൯ ∀ ^,୪௭ ௭,^

[0218] In Equation 19, ^^௭is the channel used to determine the precoder ^^௭,^and ^^^^^^^^൫^^௭^^௭,^൯ is the block error rate observed on a hypothetical downlink transmission on channel ^^௭when using the ^^௧^precoder of ^^ layers.

[0219] The methods, techniques and procedures disclosed above for determination of the PMI for two or more layers may equally or similarly be extended for PMI determination in a multi-panel scenario, in a multi- TRP scenario as well as to the use cases involving multi-TRP and multi-panels.

[0220] Channel Quality Indicators (CQIs) are discussed herein.

[0221] In solutions, a WTRU may determine a CQI value, (e.g., a wideband CQI value, a sub-band CQI value, a differential sub-band CQI value). One or more of the following may apply for determination of the CQI.

[0222] The WTRU may determine a first CQI based on the first PMI. For example, the WTRU may determine a first CQI value based on the first PMI. The CQI may be an indication of the modulation and coding scheme that could be used when transmitting on the first channel using the first set of antenna ports or using the first set of antenna ports and the common / shared antenna ports.

[0223] The WTRU may determine a second CQI based on the second PMI. For example, the WTRU may determine a second CQI value based on the second PMI. The CQI may be an indication of the modulation and coding scheme that could be used when transmitting on the second channel using all the antenna ports.

[0224] The WTRU may determine a third CQI based on the third PMI. For example, the WTRU may determine a third CQI value based on the third PMI. The CQI may be an indication of the modulation and coding scheme that could be used when transmitting on the third channel using all or partial antenna ports other than the antenna ports used for transmission of the RS.

[0225] Rank indicators are discussed herein.

[0226] First, it is worthy to highlight that the so-called rank indicator (RI) is different from the rank of the channel matrix. The RI indicates the number of layers supported by the determined PMI.

[0227] In solutions, the RI may include one or more of the following.

[0228] The RI may have two parts. The two parts may be a first RI and a second RI.

[0229] The first RI may indicate the number of layers supported by the PMI. For example, the first RI may indicate that the determined PMI supports ^^ number of layers.

[0230] The second RI may indicate a first PMI, a second PMI, or a third PMI. For example, the second RI may indicate that the determined PMI that supports ^^ layers indicated by the first RI is the ^^௧^PMI associated with the ^^௧^channel and / or with the ^^௧^set of antenna ports.

[0231] In solutions, the second RI may be a separate indicator, (e.g., separate from the RI). The second RI may be termed as the PMI number (PMIn). In examples, the PMIn indicates the PMI number, e.g., a first PMI, a second PMI, a third PMI.

[0232] CSI reporting is discussed herein.

[0233] In solutions, the WTRU may send, transmit, and / or report a CSI in a CSI-RS report, (e.g., in a periodic CSI report, in an aperiodic CSI report) in the uplink channel, (e.g., using physical uplink control channel (PUCCH) and / or physical uplink shared channel (PUSCH)). The CSI report may include indications for one or more of the following.

[0234] The CSI report may include an indication for a first component PMI.

[0235] The CSI report may include an indication for a first co-phasing value, a second co-phasing value and / or a third co-phasing value.

[0236] The CSI report may include an indication for a first CQI, a second CQI, and / or a third CQI.

[0237] The CSI report may include an indication for a RI, including the first RI and / or the second RI.

[0238] The CSI report may include an indication for a PMIn.

[0239] The CSI report may include an indication for a first rank, second rank, and / or a third rank value.

[0240] CSI prioritization is discussed herein

[0241] The available uplink time and / or frequency resources might not be sufficient to report all the content(s) of the CSI report, (e.g., the physical uplink shared channel (PUSCH) or PUCCH resources) may not be sufficient to report all CSI. The WTRU may therefore prioritize reporting one CSI over another CSI and / or drop some CSI in order to fit the CSI payload into the available resources.

[0242] In solutions, to prioritize or de-prioritize a CSI, the WTRU may do one or more of the following.

[0243] The WTRU may send an indicator in the CSI report to indicate the index of the first strongest set of antenna ports (e.g., SSAP1), second strongest set of antenna ports (e.g., SSAP2), and / or third strongest set of antenna ports (e.g., SSAP3), where one or more of the following may apply,

[0244] The first SSAP1, SSAP2, and / or SSAP3 may also be the index of the strongest CQI, the index of the strongest RI, the index of the strongest rank of the channel. In examples, if the strongest CQI may be associated with the first channel or the first PMI or the first set of ports, the strongest CQI may be assumed as an explicit indication that the first set of antenna ports is the SSAP1. In examples, if the strongest CQI is associated to the second channel or the second PMI or the second set of ports, the second strongest CQI may be assumed as an explicit indication that the second set of antenna ports is the SSAP2.

[0245] The WTRU may prioritize the CSI associated with SSAP1 over SSAP2 and SSAP3. In examples, the WTRU may prioritize reporting the strongest CQI over the second and third strongest CQIs. In examples, the WTRU may report the PMI associated with the ports in SSAP1 and may drop the PMIs associated with the ports in SSAP2 and SSAP3.

[0246] The WTRU may prioritize the CSI associated with SSAP2 over SSAP3. In examples, the WTRU may prioritize reporting the second strongest CQI over the third strongest CQI. In examples, the WTRU may report the PMI associated with the ports in SSAP2 and may drop the PMI associated with the ports in SSAP3.

[0247] WTRU assistance information is discussed herein.

[0248] The WTRU has a better view of the downlink channel as compared to the gNB as the reported CSI is quantized CSI. The performance, (e.g., throughput), CSI-RS overhead and CSI reporting overhead performance of the methods, techniques and procedures may heavily rely on grouping, partitioning, and / or dividing the antenna ports on the panel to two or more groups. For example, the CSI-RS overhead and CSI reporting overhead may depend on the number of antenna ports in the first set of antenna ports and on the number of antenna ports in the second set of antenna ports that are included in the first set of antenna ports also known as the shared / common antenna ports. The throughput performance may depend on the total number of antenna ports, the number of antenna ports in each group of antenna ports, and / or the number of groups and the number of shared / common CSI-RS ports. The throughput performance also may depend on the indices of the antenna ports in the first set of antenna ports and on the indices of the shared / common antenna ports.

[0249] In solutions, the WTRU may provide a recommendation of the first set of co-phasing values, second set of co-phasing values and / or a third set of co-phasing values based on the rate of change of co- phasing over time.

[0250] In examples, the WTRU may observe that the first co-phasing is changing at a faster rate as compared to the second and / or third co-phasing. The WTRU may provide a recommendation to change the first set of co-phasing values, (e.g., to change the first set of co-phasing values from binary phase shift keying (BPSK) to quadrature phase shift keying (QPSK)).

[0251] In solutions, the WTRU may provide a recommendation to change the number of antenna ports in the first set of antenna ports based on the rate of change of the first component PMI. For example, the WTRU may observe that the first component PMI is not changing a lot over time and provide a recommendation to the gNB in the CSI report to reduce the number of antenna ports in the first set of antenna ports to reduce CSI-RS overhead.

[0252] In examples, the WTRU may observe that the second component PMI, third component PMI, or fourth component PMI is changing at a faster rate over time. The WTRU may provide a recommendation in the form of an indication in the CSI report to increase the number of shared / common antenna ports.

[0253] A WTRU may receive a CSI configuration which includes indications for one or more of the following.

[0254] The CSI configuration may include a mapping of the CSI-RS ports to a plurality of sets. FIG.2A shows an example of CSI-RS port mapping. For example, the CSI-RS ports may be mapped to a first set of CSI-RS ports (e.g., ports represented by solid lines and dashed lines in light grey background at 202) and a second set of CSI-RS ports. (e.g., ports represented by dash-dot-dash lines and dash-dot-dot lines in dark grey background at 204).

[0255] The CSI configuration may include a mapping of the CSI-RS ports in each of the plurality of sets of CSI-RS ports to a respective multiple subsets of CSI-RS ports.

[0256] In examples, the first set of CSI-RS ports may be mapped to a first subset of CSI-RS ports and a second subset of CSI-RS ports. The first subset of CSI-RS ports associated with the first set of CSI-RS ports may include the horizontal polarizations (e.g., represented by solid lines in light grey background at 208). The second subset of CSI-RS ports associated with the first set of CSI-RS ports may include the vertical polarizations (e.g., represented by dashed lines in light grey background at 210).

[0257] The CSI configuration may include a number and / or indices of one or more shared CSI-RS ports in each of one or more of the plurality of sets of CSI-RS ports (e.g., shared ports in light grey background anddark grey backgrounds). For example, the CSI configuration may include a number and indices of one or more shared CSI-RS ports in each of the first and second sets of CSI-RS ports.

[0258] The WTRU may receive and / or measure a CSI-RS from the first set of CSI-RS ports and from the shared CSI-RS ports in each of the other (other than the first set of CSI-RS ports) set(s) of CSI-RS ports that include shared CSI-RS ports (e.g., from the shared dash-dot-dash ports at 212 and dash-dot-dot ports in the dark grey background at 214). The WTRU may perform one or more of the following based on the reception and / or measurement of the CSI-RS.

[0259] The WTRU may determine a first component PMI (e.g., PMI^), for the first subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., solid ports in light grey background).

[0260] For example, the WTRU may determine a first component PMI (e.g., PMI^) for the horizontal polarizations of the first set of CSI-RS ports (e.g., for solid ports in light grey background).

[0261] The WTRU may determine at least one of a first set of coefficients (e.g., ^^^), a second set of coefficients (e.g., ^^ଶ), and a third set of coefficients (e.g., ^^ଷ). Each set of coefficients may comprise a single co-phasing value or a vector of co-phasing values. Additionally, or alternatively each set of coefficient(s) may comprise a single amplitude scaling value or a vector of amplitude scaling values.

[0262] The first component PMI combined with one or more of the first, second and / or third sets of coefficients may indicate each of one or more of a second component PMI (e.g., for the CSI-ports in the first set with vertical polarization) (e.g., dashed ports in light grey background at 210), a third component PMI (e.g., for the CSI-ports in the second set with horizontal polarization)(e.g., for dash-dot-dash ports in dark grey background at 212) and / or a fourth component PMI (e.g., for the CSI-ports in the second set with vertical polarization) (e.g., for dash-dot-dot ports in dark grey background at 214).

[0263] The WTRU may send a CSI report which includes indications for the first component PMI and the first set of coefficient(s), the second set of coefficient(s), and / or the third set of coefficient(s).

[0264] In examples, the combination of the first component PMI with one or more of the first set of coefficient(s), the second set of coefficient(s), and / or the third sets of coefficient(s), may indicate a second component PMI (e.g., PMIଶ^, a third component PMI (e.g., PMIଷ^, and / or a fourth component PMI (e.g., PMIସ^.

[0265] The second component PMI may be for the second subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., dashed ports in light grey background at 210). The third component PMI may be for the first subset of CSI-RS ports associated with the second set of CSI-RS ports (e.g., for dash-dot-dash ports in dark grey background at 212). The fourth component PMI may be for the second subset of CSI-RSports associated with the second set of CSI-RS ports (e.g., for dash-dot-dot ports in dark grey background at 214).

[0266] In examples, the PMI may be a vector of component PMIs expressed as PMI ൌ ^PMI^, PMIଶ ൌ^^^PMI^, PMIଷ ൌ ^^ଶPMI^, PMIସ ൌ ^^^^^ଶ^^ଷ PMI^^. Each component PMI may be a vector ofcomplex coefficients. The second, third, and fourth component PMIs may be obtained by combining the first component PMI with the first (e.g., ^^^), second (e.g., ^^ଶ), and / or third (e.g., ^^ଷ) set of coefficients.

[0267] Each component PMI may be for a subset of CSI-RS ports associated with a set of antenna ports. In examples, PMI^may be for the first subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., for solid ports in light grey background at 208). PMIଶmay be for the first subset of CSI-RS ports associated with the second set of CSI-RS ports (e.g., for dashed ports in light grey background at 210). PMIଷmay be for the second subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., for dash-dot-dash ports in dark grey background at 212). PMIସmay be for the second subset of CSI-RS ports associated with the second set of CSI-RS ports (e.g., for dash-dot-dot ports in dark grey background at 214).

[0268] Each coefficient in a vector of coefficients may be for a single antenna port. In examples, the first, second, third (e.g., and so on) coefficients of the first component PMI may be for the first, second, third (e.g., and so on) CSI-RS ports in the first subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., for solid ports in light grey background at 208).

[0269] The first, second, third (e.g., and so on) coefficients of the second component PMI may be for the first, second, third (e.g., and so on) CSI-RS ports in the second subset of CSI-RS ports associated with the first set of CSI-RS ports (e.g., for dashed ports in light grey background at 210).

[0270] The first, second, third (e.g., and so on) coefficients of the third component PMI may be for the first, second, third (e.g., and so on) CSI-RS ports in the first subset of CSI-RS ports associated with the second set of CSI-RS ports (e.g., for dash-dot-dash ports in dark grey background at 212)

[0271] The first, second, third (e.g., and so on) coefficients of the fourth component PMI may be for the first, second, third (e.g., and so on) CSI-RS ports in the second subset of CSI-RS ports associated with the second set of CSI-RS ports (e.g., for dash-dot-dot ports in dark grey background at 214).

Claims

CLAIMS:

1. A wireless transmit / receive unit (WTRU) comprising a processor, wherein the processor is configured to: receive configuration information for channel state information (CSI), wherein the configuration information for CSI indicates a plurality of CSI-reference signal (RS) antenna ports, wherein the plurality of CSI-RS antenna ports comprises at least a first set of CSI-RS antenna ports and a second set of CSI-RS antenna ports, wherein the first set of CSI-RS antenna ports comprises one or more subsets of CSI-RS antenna ports and the second set of CSI-RS antenna ports comprises one or more subsets of CSI-RS antenna ports; measure one or more CSI-RSs that are associated with the first set of CSI-RS antenna ports; determine a first component precoding matrix indicator (PMI) for a first subset of the first set of CSI-RS antenna ports; determine a first set of coefficients for the first set of CSI-RS antenna ports; determine a second set of coefficients for the second set of CSI-RS antenna ports; and send a CSI report that includes at least one of the first component PMI, the first set of coefficients, or the second set of coefficients.

2. The WTRU of claim 1, wherein the first subset of the first set of CSI-RS antenna ports is comprised of CSI-RS antenna ports of the first set of CSI-RS ports which have a horizontal polarization or a vertical polarization.

3. The WTRU of claim 1, wherein the first set of coefficients for the first set of CSI-RS antenna ports comprises a co-phasing value or an amplitude scaling value.

4. The WTRU of claim 1, wherein the configuration information indicates a set of shared CSI-RS antenna ports, the shared CSI-RS antenna ports being associated with both the first set of CSI-RS antenna ports and the second set of CSI-RS antenna ports.

5. The WTRU of claim 4, wherein the processor is configured to measure one or more CSI-RSs that are associated with the set of shared CSI-RS antenna ports.

6. The WTRU of claim 5, wherein the processor is configured to determine the first component PMI, the first set of coefficients, and the second set of coefficients based on measurements of the one or more CSI-RSs that are associated with the first set of CSI-RS antenna ports and the one or more CSI-RSs that are associated with the shared CSI-RS antenna ports.

7. The WTRU of claim 1, wherein the processor is configured to determine a second component PMI for a second subset of the first set of CSI-RS antenna ports, using at least the first set of coefficients.

8. The WTRU of claim 7, wherein the processor is configured to determine a third component PMI for a first subset of the second set of CSI-RS antenna ports, using at least the second set of coefficients.

9. The WTRU of claim 8, wherein the processor is configured to determine a fourth component PMI for a second subset of the second set of CSI-RS antenna ports, using at least the second set of coefficients.

10. The WTRU of claim 9, wherein the processor is configured to determine a PMI for the first set of CSI-RS antenna ports and the second set of CSI-RS antenna ports based on the first component PMI, the second component PMI, the third component PMI, and the fourth component PMI.

11. A method for use in a wireless transmit / receive unit (WTRU), the method comprising: receiving configuration information for channel state information (CSI), wherein the configuration information for CSI indicates a plurality of CSI-reference signal (RS) antenna ports, wherein the plurality of CSI-RS antenna ports comprises at least a first set of CSI-RS antenna ports and a second set of CSI-RS antenna ports, wherein the first set of CSI-RS antenna ports comprises one or more subsets of CSI-RS antenna ports and the second set of CSI-RS antenna ports comprises one or more subsets of CSI-RS antenna ports; measuring one or more CSI-RSs that are associated with the first set of CSI-RS antenna ports; determining a first component precoding matrix indicator (PMI) for a first subset of the first set of CSI-RS antenna ports; determining a first set of coefficients for the first set of CSI-RS antenna ports;determining a second set of coefficients for the second set of CSI-RS antenna ports; and sending a CSI report that includes at least one of the first component PMI, the first set of coefficients, or the second set of coefficients.

12. The method of claim 11, wherein the first subset of the first set of CSI-RS antenna ports is comprised of CSI-RS antenna ports of the first set of CSI-RS ports which have a horizontal polarization or a vertical polarization.

13. The method of claim 11, wherein the first set of coefficients for the first set of CSI-RS antenna ports comprises a co-phasing value or an amplitude scaling value.

14. The method of claim 11, wherein the configuration information indicates a set of shared CSI-RS antenna ports, the shared CSI-RS antenna ports being associated with both the first set of CSI-RS antenna ports and the second set of CSI-RS antenna ports.

15. The method of claim 14, further comprising measuring one or more CSI-RSs that are associated with the set of shared CSI-RS antenna ports.

16. The method of claim 15, further comprising determining the first component PMI, the first set of coefficients, and the second set of coefficients based on measurements of the one or more CSI-RSs that are associated with the first set of CSI-RS antenna ports and the one or more CSI-RSs that are associated with the shared CSI-RS antenna ports.

17. The method of claim 11, further comprising determining a second component PMI for a second subset of the first set of CSI-RS antenna ports, using at least the first set of coefficients.

18. The method of claim 17, further comprising determining a third component PMI for a first subset of the second set of CSI-RS antenna ports, using at least the second set of coefficients.

19. The method of claim 18, further comprising determining a fourth component PMI for a second subset of the second set of CSI-RS antenna ports, using at least the second set of coefficients.

20. The method of claim 19, further comprising determining a PMI for the first set of CSI-RS antenna ports and the second set of CSI-RS antenna ports is determined based on the first component PMI, the second component PMI, the third component PMI, and the fourth component PMI.

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