WO2025010199A1

WO2025010199A1 - Methods, architectures, apparatuses and systems for differential channel state information compression and feedback on mismatch detection

Info

Publication number: WO2025010199A1
Application number: PCT/US2024/036102
Authority: WO
Inventors: Ahmet Serdar Tan; Patrick Tooher; Tejaswinee LUTCHOOMUN; Mihaela Beluri
Original assignee: InterDigital Patent Holdings Inc
Current assignee: InterDigital Patent Holdings Inc
Priority date: 2023-07-05
Filing date: 2024-06-28
Publication date: 2025-01-09
Anticipated expiration: 2026-01-05
Also published as: TW202504283A

Abstract

A method, implemented in a wireless transmit and receive unit (WTRU), may include receiving one or more reference signals, selecting a first codebook-based precoding matrix based on the one or more reference signals and determining a second precoding matrix based on the one or more reference signals. The method may include determining a differential precoding matrix based on the first codebook-based precoding matrix and the second precoding matrix. The method may include determining a compressed differential precoding matrix based on the differential precoding matrix. The method may include transmitting feedback information indicating the compressed differential precoding matrix.

Description

METHODS, ARCHITECTURES, APPARATUSES AND SYSTEMS FOR DIFFERENTIAL CHANNEL STATE INFORMATION COMPRESSION AND FEEDBACK ON MISMATCH DETECTION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application Nos. 63/525,009, filed July 5, 2023; and 63/536,988, filed September 7, 2023, each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure is generally directed to the fields of communications, software and encoding, including methods, architectures, apparatuses, and systems directed to differential channel state information (CSI) compression and feedback.

BACKGROUND

[0003] Codebook-based precoding with feedback information transmission may be used in wireless systems. Performance of codebook-based precoding may be limited due to its finite number of precoding vectors. Embodiments described herein have been designed with the foregoing in mind.

BRIEF SUMMARY

[0004] Methods, architectures, apparatuses, and systems directed to differential channel state information (CSI) compression and feedback are described herein. In an embodiment, a first method implemented in a wireless transmit/receive unit (WTRU) is described herein. The first method may include receiving one or more reference signals. The first method may include determining (e.g., selecting) a first codebook-based precoding matrix and determining a second precoding matrix based on the one or more reference signals. The first method may include determining a differential CSI (e.g., differential precoding matrix) based on the first codebookbased precoding matrix and the second precoding matrix. The first method may include determining a compressed differential CSI (e.g., compressed differential precoding matrix) based on the differential CSI (e.g., differential precoding matrix). The first method may include transmitting feedback information indicating the compressed differential CSI (e.g., compressed differential precoding matrix).

[0005] In an embodiment, a second method implemented in a WTRU is described herein. The second method may include receiving one or more reference signals and determining a second precoding matrix based on the one or more reference signals. The second method may include determining one or more parameters for codebook-based precoding matrix and differential CSI compression based on the second precoding matrix. The second method may include determining a first precoding matrix based on the one or more reference signals and the determined one or more parameters. The second method may include determining a compressed differential CSI (e.g., compressed differential precoding matrix) based on the first precoding matrix, the second precoding matrix and the determined one or more parameters. The second method may include transmitting feedback information indicating the compressed differential CSI (e.g., compressed differential precoding matrix) and the determined one or more parameters.

[0006] In an embodiment, a third method implemented in a WTRU is described herein. The third method may include receiving a first reference signal at a first time instance at a beginning of a time window and determining a first precoding matrix based on the first reference signal. The third method may include receiving a second reference signal at a second time instance within the time window and determining a second precoding matrix based on the second reference signal. The third method may include determining a second compressed differential CSI (e.g., compressed differential precoding matrix) based on the first precoding matrix and the second precoding matrix. The third method may include transmitting first feedback information at a first reporting occasion associated with the first time instance, and the first feedback information may indicate the first precoding matrix. The third method may include transmitting second feedback information at a second reporting occasion associated with the second time instance, and the second feedback information may indicate the second compressed differential CSI (e.g., compressed differential precoding matrix).

[0007] In an embodiment, a fourth method implemented in a WTRU is described herein. The fourth method may include receiving a plurality of reference signals from a plurality of network elements. The fourth method may include determining at least one first precoding matrix for at least one network element of the plurality of network elements and determining a plurality of second precoding matrices for the plurality of network elements based on the plurality of reference signals. The fourth method may include determining a plurality of differential CSI elements based on the at least one first precoding matrix and the plurality of second precoding matrices. The fourth method may include determining a jointly compressed differential CSI based on the plurality of differential CSI elements and transmitting feedback information indicating the jointly compressed differential CSI.

[0008] In an embodiment, a first WTRU including circuitry including any of a processor, a transmitter, a receiver and a memory is described herein. The circuitry may be configured to receive one or more reference signals. The circuitry may be configured to determine (e.g., select) a first codebook-based precoding matrix and to determine a second precoding matrix based on the one or more reference signals. The circuitry may be configured to determine a differential CSI (e.g., differential precoding matrix) based on the first codebook-based precoding matrix and the second precoding matrix. The circuitry may be configured to determine a compressed differential CSI (e.g., compressed differential precoding matrix) based on the differential CSI (e.g., differential precoding matrix). The circuitry may be configured to transmit feedback information indicating the compressed differential CSI (e.g., compressed differential precoding matrix).

[0009] In an embodiment, a second WTRU including circuitry including any of a processor, a transmitter, a receiver and a memory is described herein. The circuitry may be configured to receive one or more reference signals and to determine a second precoding matrix based on the one or more reference signals. The circuitry may be configured to determine one or more parameters for codebook-based precoding matrix and differential CSI compression based on the second precoding matrix. The circuitry may be configured to determine a first precoding matrix based on the one or more reference signals and the determined one or more parameters. The circuitry may be configured to determine a compressed differential CSI (e.g., compressed differential precoding matrix) based on the first precoding matrix, the second precoding matrix and the determined one or more parameters. The circuitry may be configured to transmit feedback information indicating the compressed differential CSI (e.g., compressed differential precoding matrix) and the determined one or more parameters.

[0010] In an embodiment, a third WTRU including circuitry including any of a processor, a transmitter, a receiver and a memory is described herein. The circuitry may be configured to receive a first reference signal at a first time instance at a beginning of a time window and to determine a first precoding matrix based on the first reference signal. The circuitry may be configured to receive a second reference signal at a second time instance within the time window and to determine a second precoding matrix based on the second reference signal. The circuitry may be configured to determine a second compressed differential CSI (e.g., compressed differential precoding matrix) based on the first precoding matrix and the second precoding matrix. The circuitry may be configured to transmit first feedback information at a first reporting occasion associated with the first time instance, and the first feedback information may indicate the first precoding matrix. The circuitry may be configured to transmit second feedback information at a second reporting occasion associated with the second time instance, and the second feedback information may indicate the second compressed differential CSI (e.g., compressed differential precoding matrix).

[0011] In an embodiment, a fourth WTRU including circuitry including any of a processor, a transmitter, a receiver and a memory is described herein. The circuitry may be configured to receive a plurality of reference signals from a plurality of network elements. The circuitry may be configured to determine at least one first precoding matrix for at least one network element of the plurality of network elements and to determine a plurality of second precoding matrices for the plurality of network elements based on the plurality of reference signals. The circuitry may be configured to determine a plurality of differential CSI elements based on the at least one first precoding matrix and the plurality of second precoding matrices. The circuitry may be configured to determine a jointly compressed differential CSI based on the plurality of differential CSI elements and transmitting feedback information indicating the jointly compressed differential CSI.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] A more detailed understanding may be had from the detailed description below, given by way of example in conjunction with drawings appended hereto. Figures in such drawings, like the detailed description, are examples. As such, the Figures (FIGs.) and the detailed description are not to be considered limiting, and other equally effective examples are possible and likely. Furthermore, like reference numerals ("ref.") in the FIGs. indicate like elements, and wherein: [0013] FIG. 1 A is a system diagram illustrating an example communications system;

[0014] FIG. IB is a system diagram illustrating an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1 A;

[0015] 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;

[0016] FIG. ID 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. 1 A;

[0017] FIG. 2 is a diagram illustrating an example of codebook-based precoding with feedback information;

[0018] FIG. 3 is a diagram illustrating an example of artificial intelligence / machine learning (AI/ML) framework for CSI feedback compression;

[0019] FIG. 4 is a diagram illustrating an example procedure for differential CSI compression and feedback;

[0020] FIG. 5 is a diagram illustrating an example procedure at the network side for differential CSI compression;

[0021] FIG. 6 is a diagram illustrating an example of windowed differential CSI compression;

[0022] FIG. 7 is a diagram illustrating an example method for window differential CSI compression;

[0023] FIG. 8 is a diagram illustrating an example of non-anchor-based joint CSI compression;

[0024] FIG. 9 is a diagram illustrating an example of anchor-based joint CSI compression;

[0025] FIG. 10 is a diagram illustrating an example method for differential CSI compression and feedback on mismatch detection; [0026] FIG. 11 is a diagram illustrating an example method for differential CSI compression;

[0027] FIG. 12 is diagram illustrating an example method for reporting parameters for differential CSI compression;

[0028] FIG. 13 is a diagram illustrating an example method for using windowing to determine differential CSI compression; and

[0029] FIG. 14 is a diagram illustrating an example method for joint differential CSI compression for multi-transmit and receive point (TRP).

DETAILED DESCRIPTION

[0030] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of embodiments and/or examples disclosed herein. However, it will be understood that such embodiments and examples may be practiced without some or all of the specific details set forth herein. In other instances, well-known methods, procedures, components and circuits have not been described in detail, so as not to obscure the following description. Further, embodiments and examples not specifically described herein may be practiced in lieu of, or in combination with, the embodiments and other examples described, disclosed or otherwise provided explicitly, implicitly and/or inherently (collectively "provided") herein. Although various embodiments are described and/or claimed herein in which an apparatus, system, device, etc. and/or any element thereof carries out an operation, process, algorithm, function, etc. and/or any portion thereof, it is to be understood that any embodiments described and/or claimed herein assume that any apparatus, system, device, etc. and/or any element thereof is configured to carry out any operation, process, algorithm, function, etc. and/or any portion thereof.

Example Communications System

[0031] The methods, apparatuses and systems provided herein are well-suited for communications involving both wired and wireless networks. An overview of various types of wireless devices and infrastructure is provided with respect to FIGs. 1A-1D, where various elements of the network may utilize, perform, be arranged in accordance with and/or be adapted and/or configured for the methods, apparatuses and systems provided herein.

[0032] FIG. 1A is a system 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), singlecarrier FDMA (SC-FDMA), zero-tail (ZT) unique-word (UW) discrete Fourier transform (DFT) spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block- filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0033] As shown in FIG. 1A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104/113, a core network (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 (or be) 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 (loT) 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 UE.

[0034] 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, e.g., to facilitate access to one or more communication networks, such as the CN 106/115, the Internet 110, and/or the networks 112. By way of example, the base stations 114a, 114b may be any of a base transceiver station (BTS), a Node-B (NB), an eNode-B (eNB), a Home Node-B (HNB), a Home eNode-B (HeNB), a gNode-B (gNB), a NR Node-B (NR NB), 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.

[0035] 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 an 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 or any sector of the cell. For example, beamforming may be used to transmit and/or receive signals in desired spatial directions.

[0036] 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).

[0037] 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 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

[0038] 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).

[0039] 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).

[0040] 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).

[0041] In an embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (Wi-Fi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 IX, 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.

[0042] The base station 114b in FIG. 1 A 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 an 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 an embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish any of a small cell, picocell or femtocell. As shown in FIG. 1 A, 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.

[0043] 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. 1 A, 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 an NR radio technology, the CN 106/115 may also be in communication with another RAN (not shown) employing any of a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or Wi-Fi radio technology. [0044] 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 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 104/114 or a different RAT.

[0045] 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.

[0046] FIG. IB is a system diagram illustrating an example WTRU 102. As shown in FIG. IB, 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 elements/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.

[0047] 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. IB 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, e.g., in an electronic package or chip. [0048] 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 an 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 an 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.

[0049] Although the transmit/receive element 122 is depicted in FIG. IB as a single element, the WTRU 102 may include any number of transmit/receive elements 122. For example, the WTRU 102 may employ MIMO technology. Thus, in an 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.

[0050] 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/receive element 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.

[0051] 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), readonly 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).

[0052] 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. [0053] 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.

[0054] The processor 118 may further be coupled to other elements/peripherals 138, which may include one or more software and/or hardware modules/units that provide additional features, functionality and/or wired or wireless connectivity. For example, the elements/peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (e.g., 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 frequency modulated (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 elements/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.

[0055] 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 uplink (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 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 WTRU 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 uplink (e.g., for transmission) or the downlink (e.g., for reception)).

[0056] 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, and 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106. [0057] 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 an 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 receive wireless signals from, the WTRU 102a.

[0058] Each of the eNode-Bs 160a, 160b, and 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 uplink (UL) and/or downlink (DL), and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface. [0059] 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 (PGW) 166. While each of the foregoing elements are depicted as part of the CN 106, it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the CN operator.

[0060] The MME 162 may be connected to each of the eNode-Bs 160a, 160b, and 160c in the RAN 104 via an SI 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.

[0061] The SGW 164 may be connected to each of the eNode-Bs 160a, 160b, 160c in the RAN 104 via the SI 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.

[0062] 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.

[0063] 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.

[0064] 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. [0065] In representative embodiments, the other network 112 may be a WLAN.

[0066] 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 into and/or out of the 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. l ie DLS or an 802.1 Iz 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.

[0067] When using the 802.1 lac 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. [0068] 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 nonadj acent 20 MHz channel to form a 40 MHz wide channel.

[0069] Very high throughput (VHT) STAs may support 20 MHz, 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, the above-described operation for the 80+80 configuration may be reversed, and the combined data may be sent to a medium access control (MAC) layer, entity, etc.

[0070] Sub 1 GHz modes of operation are supported by 802.1 laf and 802.11 ah. The channel operating bandwidths, and carriers, are reduced in 802.1 laf and 802.1 lah relative to those used in

802.1 In, and 802.1 lac. 802.1 laf supports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV white space (TVWS) spectrum, and 802.1 lah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment,

802.1 lah may support meter type control/machine-type communications (MTC), 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).

[0071] WLAN systems, which may support multiple channels, and channel bandwidths, such as

802.1 In, 802.1 lac, 802.1 laf, and 802.1 lah, 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 802.1 lah, 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.

[0072] In the United States, the available frequency bands, which may be used by 802.1 lah, 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 802.1 lah is 6 MHz to 26 MHz depending on the country code.

[0073] FIG. ID 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 CN 115.

[0074] 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 an embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 180b may utilize beamforming to transmit signals to and/or receive signals from the WTRUs 102a, 102b, 102c. 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).

[0075] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a scalable numerology. For example, OFDM symbol spacing and/or OFDM subcarrier spacing may vary for different transmissions, different cells, and/or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., including a varying number of OFDM symbols and/or lasting varying lengths of absolute time).

[0076] 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 serve as 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.

[0077] 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 functions (UPFs) 184a, 184b, routing of control plane information towards access and mobility management functions (AMFs) 182a, 182b, and the like. As shown in FIG. ID, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0078] The CN 115 shown in FIG. ID may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one session management function (SMF) 183a, 183b, and at least one 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.

[0079] 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 protocol data unit (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, e.g., 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 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.

[0080] 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 UE 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.

[0081] 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, e.g., 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 multihomed PDU sessions, handling user plane QoS, buffering downlink packets, providing mobility anchoring, and the like.

[0082] 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 an 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.

[0083] In view of FIGs. 1 A-1D, and the corresponding description of FIGs. 1 A-1D, one or more, or all, of the functions described herein with regard to any of: WTRUs 102a-d, base stations 114a- b, eNode-Bs 160a-c, MME 162, SGW 164, PGW 166, gNBs 180a-c, AMFs 182a-b, UPFs 184a- b, SMFs 183a-b, DNs 185a-b, and/or any other element(s)/device(s) described herein, may be performed by one or more emulation elements/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.

[0084] 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.

[0085] 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.

[0086] Throughout embodiments described herein the terms "base station", "network", “NW” and "gNB", collectively "the network" may be used interchangeably to designate any network element such as e.g., a network element acting as a serving base station. Embodiments described herein are not limited to gNBs and are applicable to any other type of base stations.

[0087] For the sake of clarity, satisfying, failing to satisfy a condition, and configuring condition parameter(s) are described throughout embodiments described herein as relative to a threshold (e.g., greater, or lower than) a (e.g., threshold) value, configuring the (e.g., threshold) value, etc. For example, satisfying a condition may be described as being above a (e.g., threshold) value, and failing to satisfy a condition may be described as being below a (e.g., threshold) value. Embodiments described herein are not limited to threshold-based conditions. Any kind of other condition and param eter(s) (such as e.g., belonging or not belonging to a range of values) may be applicable to embodiments described herein.

[0088] Throughout embodiments described herein, (e.g., configuration) information may be described as received by a WTRU from the network, for example, through system information or via any kind of protocol message. Although not explicitly mentioned throughout embodiments described herein, the same (e.g., configuration) information may be pre-configured in the WTRU (e.g., via any kind of pre-configuration methods such as e.g., via factory settings), such that this (e.g., configuration) information may be used by the WTRU without being received from the network.

[0089] Throughout embodiments described herein, the expression "a WTRU may be configured with something" may be used interchangeably with "a WTRU may receive configuration information indicating something". Throughout embodiments described herein, the expression "a WTRU may report something" may be used interchangeably with "a WTRU may transmit (e.g., reporting) information indicating something". Throughout embodiments described herein, the expression "a WTRU may feedback something" may be used interchangeably with "a WTRU may transmit (e.g., feedback) information indicating something".

[0090] Methods to mitigate the performance degradation resulting from limited resolution codebook-based precoding, and from CSI reconstruction errors occurring with two-sided CSI compression systems are described herein.

CSI Reporting

[0091] FIG. 2 is a diagram illustrating an example of codebook-based precoding with feedback information. The feedback information may include a precoding matrix index (PMI) which may be referred to as a codeword index in the codebook as shown in FIG. 2.

[0092] As shown in FIG. 2, a codebook may include a set of precoding vectors/matrices for each rank and the number of antenna ports. Each precoding vector/ matrix may be associated with an index such that a receiver may indicate preferred precoding vector/matrix index to a transmitter. The codebook-based precoding may have performance degradation based on its finite number of precoding vector/matrix as compared with non-codebook-based precoding. Codebook-based precoding may allow a lower control signaling (e.g., feedback) overhead.

AI/ML based CSI Feedback

[0093] Artificial Intelligence and/or machine learning (AI/ML) based CSI feedback may use autoencoders (AE) for CSI compression. This may be seen as a two-sided system, where the estimated CSI may be compressed at the WTRU side, fed back to the gNB, and then decompressed at the gNB. Autoencoders (AE) may be seen as two-sided AI/ML models comprising an encoder and the corresponding decoder. For CSI compression, the encoder part of the AE may reside at the WTRU-side, and the decoder part of the AE may reside at the NW-side. The encoder may perform the compression functionality. The autoencoder (AE) may perform the end-to-end compression and reconstruction functionality.

[0094] FIG. 3 is a diagram illustrating an example of AI/ML framework for CSI feedback compression. AI/ML based CSI compression may allow a performance improvement compared to legacy CSI feedback using a similar payload size. AI/ML based CSI feedback may be associated with a compression error that may (e.g., occasionally) lead to (e.g., significant) mismatch between the precoder computed at the WTRU and decompressed precoder at NW, X and X.

Overview [0095] Embodiments described herein may allow to handle mismatch and performance degradation in CSI compression.

[0096] Based on the two-sided nature of AI/ML-based CSI feedback, a mismatch may occur between the precoder calculated at the WTRU-side (X) and the precoder restored at the NW-side X. Occasional mismatch may lead to performance degradation, as the NW may make any of precoding and scheduling decisions based on a potentially different precoder (X , where X X). In case of a (e.g., significant) mismatch the corresponding transport blocks may not be successfully decoded.

[0097] In the legacy CSI framework, there are no mismatch errors. Using only type I/II PMI for CSI feedback may result in performance degradation compared to CSI compression.

[0098] A balanced solution may allow to handle performance and mismatch issues.

[0099] Embodiments described herein may allow to enable a balanced solution that may address at the same time (i) CSI compression mismatch and (ii) performance degradation based on using only codebook-based precoding.

[0100] A WTRU may be enabled with multi-TRP transmissions. The WTRU may (e.g., be required to) feedback CSI report for each TRP. The CSI reporting overhead may represent a bottle neck for CSI reporting in multi-TRP transmissions. For example, to enable the coherent joint transmission (CJT) with multi-TRP, high precision CSI may be expected at the NW.

[0101] Embodiments described herein may allow to address mismatch issues and to further increase the precision of CSI report for multi-TRP (e.g., transmissions).

Overview of Differential CSI Compression and Feedback on Mismatch Detection

[0102] In an embodiment, a WTRU may determine (e.g., compute) compressed differential CSI based on the difference between ideal CSI and low-resolution codebook-based CSI. The WTRU may report any of compressed differential CSI, PMI and mismatch metric.

[0103] In a first step, the WTRU may receive configuration information on differential CSI compression indicating any of (a) the payload size low-resolution precoder matrix (PM) feedback (e.g., Type VII PMI feedback), (b) the payload size of differential CSI compression, (c) an indication on the use of differential CSI compression, (d) any of uplink resources and resource types for different parts of CSI report, and (e) rules (e.g., configurations) for the WTRU to determine the reporting configurations (e.g., for CSI report part 1, use configured grant (CG) configuration 1, for CSI report part 2, use CG configuration 2. Or for CSI report part 1, use the currently activated CG configuration, for CSI report part 2, request for additional resources (e.g., via any of scheduling request (SR) and buffer status report (BSR)).

[0104] In a second step, the WTRU may receive a CSI reference signal (RS) and may determine (e.g., compute) the differential CSI. zu [0105] For example, the WTRU may determine (e.g., compute, select) a low-resolution (e.g., low payload size) Type I/II codebook-based precoding matrix (PM) according to the indicated configuration based on CSI-RS measurements. The low-resolution PM may correspond to a wideband channel. In an example, a codebook-based precoding matrix may be selected from a set of (e.g., configured) codebook-based precoding matrices.

[0106] For example, the WTRU may determine (e.g., compute) one or more ideal precoding matrix(ces) based on CSI-RS measurements. The ideal PM may correspond to a sub-band channel. [0107] For example, the WTRU may determine (e.g., compute) two channel quality indicators (CQIs): CQI l for low resolution codebook-based PM and CQI 2 for ideal PM.

[0108] For example, the WTRU may determine (e.g., compute) the one or more difference of codebook-based precoding matrix and ideal precoding matrix, e.g., the differential CSI (e.g., one per sub-band).

[0109] For example, the WTRU may compress the one or more differential CSI (e.g., using a trained AE) based on the indicated payload size.

[0110] For example, the WTRU may determine (e.g., compute) one or more side information(s) for the detection of mismatch at NW side.

[OHl] In a third step, the WTRU may determine the feedback.

[0112] In a case where the WTRU reports one CSI report based on configuration, the WTRU may report the low-resolution PM and one or more compressed differential CSI. The WTRU may report the one or more side information(s) for mismatch detection. The WTRU may report one or more CQI values. The WTRU may report (e.g., only) the low-resolution PM if the difference between codebook based PM and ideal PM is low (e.g., is lower than a threshold).

[0113] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may receive (e.g., information indicating a) differential CSI request 1 from the NW that may indicate resources to be used for the feedback. The WTRU may determine priorities for different CSI reports, e.g., based on any of available uplink resources, channel conditions, etc. The WTRU may determine to report CSI Report 1 on next available uplink grant based on the determined priorities of the two CSI reports.

[0114] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may feedback CSI Report Part 1 including any of PMI and two CQI values, mismatch metric (corresponding to codebook based PM and ideal PM).

[0115] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may receive (e.g., information indicating a) differential CSI request 2 from the NW, (e.g., based on the decision given by NW considering the two CQIs). The request (e.g., information) may indicate any of physical uplink shared channel (PUSCH) and physical uplink control channel (PUCCH) resources to be used for feedback.

[0116] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may feedback CSI report Part 2 including any of the one or more compressed differential PM and one or more side information on mismatch metric.

[0117] In a fourth step, the WTRU may receive data precoded with codebook-based low- resolution PM or reconstructed ideal PM.

Overview of Determining and Reporting the Parameters of Differential CSI Compression

In an embodiment, a WTRU may determine the parameters of differential CSI compression as a function of any of (e.g., total) payload size and channel conditions. The WTRU may report the determined parameters.

[0118] In a first step, the WTRU may receive configuration information on differential CSI indicating any of (a) the total payload size of CSI report, (b), an indication on the use of differential CSI compression and (c) an indication on the WTRU to determine and report low resolution PMI and differential CSI compression parameters.

[0119] In a second step, the WTRU may receive CSI-RS and may determine (e.g., compute) the differential CSI.

[0120] For example, the WTRU may determine (e.g., compute) an ideal precoding matrix based on CSI-RS measurements.

[0121] For example, the WTRU may determine the parameters (e.g., any of payload sizes, type of side information, code-book type for PMI) for low resolution PM and differential CSI compression, based on any of (i) a table of (e.g., allowed) values, (ii) a use of a decoder/decompressor (e.g., a proxy decoder/decompressor), (iii) a performance metric calculation (e.g., squared generalized cosine similarity (SGCS), minimum payload size), and (iv) a feedback report type.

[0122] For example, the WTRU may determine (e.g., compute) the codebook-based precoding matrix based on determined parameters.

[0123] For example, the WTRU may determine (e.g., compute) the difference of codebook-based precoding matrix and ideal precoding matrix, e.g., the differential CSI.

[0124] For example, the WTRU may compress the differential CSI using (e.g., an AE-based) compression based on the determined parameters.

[0125] For example, the WTRU may determine (e.g., compute) side information based on the determined parameters for the detection of mismatch at NW side.

[0126] In a third step, the WTRU may report any of (a) the determined parameters (e.g., any of payload sizes, type of side information, code-book type for PMI) for differential CSI compression, (b) the low-resolution PM and compressed differential PM, and (iii) the side information (e.g., for mismatch detection).

Overview of Windowed Differential CSI Compression

[0127] In an embodiment, a WTRU may determine (e.g., compute) compressed differential CSI, based on the difference between current ideal CSI and a past codebook-based CSI depending on the window size. At a (e.g., each) reporting instant, the WTRU may report any of compressed differential CSI and mismatch metric, and at the beginning of a reporting window, the WTRU may report a PMI.

[0128] In a first step, the WTRU may receive configuration information on differential CSI indicating any of (a) the payload size of low-resolution PM (e.g., Type I/II PMI feedback), (b) the payload size of differential CSI compression, (c) an indication on the use of differential CSI compression, and (d) an indication on the window size to report low resolution PM and differential CSI (or an indication on the WTRU to determine the window size).

[0129] In a second step, the WTRU may receive CSI-RS and may determine (e.g., compute) the differential CSI.

[0130] For example, the WTRU may select a window size based on any of an indication from the NW and the channel coherence time.

[0131] For example, the WTRU may determine (e.g., compute) a low-resolution (e.g., low payload size) Type I/II codebook-based precoding matrix according to the indicated configuration (e.g., only) for the beginning of the indicated window, based on received CSI-RS.

[0132] For example, the WTRU may determine (e.g., compute) ideal precoding matrix based on one or more CSI-RS measurements.

[0133] For example, the WTRU may determine (e.g., compute) the difference of codebook-based precoding matrix (computed at the beginning of the window) and ideal precoding matrix, e.g., the windowed differential CSI, computed at a plurality of time instances within the window.

[0134] For example, the WTRU may compress the differential CSI (e.g., using a trained AE) based on the indicated payload size.

[0135] For example, the WTRU may determine (e.g., compute) a side information for the detection of mismatch at NW side.

[0136] In a third step, the WTRU may determine the feedback. The WTRU may report the low- resolution PM at the beginning of the window. The WTRU may report compressed differential CSI at a (e.g., every) reporting instance within the window. The WTRU may report a new low- resolution PM within a window in case of an error during the transmission of the first low resolution PM. The WTRU may report the selected window size. [0137] In a fourth step, the WTRU may receive data precoded with codebook-based low- resolution PM or reconstructed ideal PM.

Terminology

[0138] In embodiments described herein, differential CSI compression may refer to the compression of the difference of two different precoding matrices. In embodiments described herein, differential CSI and differential precoding matrix may be used interchangeably. In embodiments described herein, a compressed differential CSI and a compressed differential precoding matrix may be used interchangeably.

[0139] In embodiments described herein, a precoding matrix (PM) may refer to a matrix generated based on channel measurements to achieve (e.g., operate) beamforming. In embodiments described herein, a precoding matrix indicator (PMI) may refer to an index indicating a (e.g., specific) precoding matrix on a codebook of precoding matrices.

[0140] In embodiments described herein, a codebook-based precoding matrix may refer to the use of the (e.g., legacy) CSI feedback Typel/II mechanisms where PMI may be fed back from the WTRU to the NW. Legacy CSI feedback may refer to any of existing Typel/II, eTypell, etc. mechanisms. In embodiments described herein, the terms “codebook-based precoding matrix”, “low-resolution precoding matrix” and “lower resolution precoding matrix” may be used interchangeably.

[0141] In embodiments described herein, full CSI compression may refer to the case where the WTRU may compress the precoding matrix determined (e.g., computed) based on channel measurements at the WTRU, using (e.g., based on) the autoencoder.

[0142] In embodiments described herein, an ideal precoding matrix may refer to the precoder determined (e.g., computed) at the WTRU based on the channel measurements at the WTRU. In embodiments described herein, the terms “ideal precoding matrix”, “high-resolution precoding matrix”, “higher resolution precoding matrix”, “non-codebook-based precoding matrix”, and “WTRU-computed-based precoding matrix” may be used interchangeably.

[0143] In embodiments described herein, any of a reconstructed, a decoded and a decompressed precoding matrix may refer to the matrix obtained at the output of the decoder of autoencoder at the NW.

[0144] In embodiments described herein, mismatch may refer to a (e.g., significant) difference at the input of autoencoder at the WTRU and the output of the autoencoder at the NW that may degrade the performance of communication between the WTRU and NW.

[0145] In embodiments described herein, side information may refer to additional information (such as e.g., magnitude or relative magnitude of the input of the autoencoder) that may be sent by the WTRU to NW to detect mismatch at the NW (e.g., significant difference between input and output of the autoencoder).

[0146] In embodiments described herein, the terms channel response, channel matrix, and channel response matrix may be used interchangeably.

[0147] In embodiments described herein, the terms “low-resolution PMI”, “low-resolution CSI feedback”, “low-resolution type I/type II/enhanced type II codebook” may be used interchangeably.

[0148] In embodiments described herein, values and parameters that may be any of configured, measured, and reported may be any of indices, identifiers, relative values, absolute values, arrays of values (and/or bits), quantized values and arrays of quantized values.

[0149] In embodiments described herein the terms determining and computing may be used interchangeably.

[0150] Embodiments described herein allow to address at the same time: (i) the performance degradation of codebook-based CSI reporting, and (ii) the mismatch detection at the NW (e.g., when using autoencoder based CSI compression for CSI reporting). At the transmitting side (e.g., WTRU), embodiments described herein may enable the use of a lower complexity compression mechanism to compress the differential CSI owing to sparsity. At the receiving side (e.g., WTRU, gNB), embodiments described herein may enable the reconstruction of ideal CSI or a codebookbased CSI depending on the mismatch, using the same CSI feedback.

[0151] In embodiments described herein the terms “TRP” and “network element” may be used interchangeably to refer to a network element capable of receiving and transmitting over a network.

Differential CSI Compression and Feedback on Mismatch Detection

[0152] An example method for differential CSI compression and feedback on mismatch detection is described herein.

WTRU Configuration for Differential CSI Compression

[0153] An example of WTRU configuration for differential compression is described herein.

WTRU Configuration for Single CSI Report

[0154] The WTRU may receive configuration information on the procedures for differential CSI compression.

[0155] The WTRU may receive configuration information indicating the type of codebook-based PMI feedback, such as e.g., Typel/II, eTypell, etc. The WTRU may receive configuration information indicating the parameters of the PMI feedback, such as e.g., any of a resolution, a payload size, etc. [0156] The WTRU may receive configuration information indicating a payload size of the compressed differential CSI feedback. The WTRU may receive configuration information indicating the identifier of an AI/ML model to be used for compression. The WTRU may (e.g., also) be configured with an AI/ML model to be used for compression.

[0157] The WTRU may receive configuration information indicating whether the use of differential CSI compression that may be expected for the WTRU and NW may be to be aligned on the CSI feedback mechanism. In case the WTRU is configured to use differential CSI, then the CSI may be compressed based on the procedures described herein.

[0158] The WTRU may receive configuration information on the side information including the method for determining (e.g., computing) the side information and/or quantization level. The configuration information indicating the method to be used for determining (e.g., computing) the side information may determine the type of mismatch detection (e.g., to be used) at the NW. The configuration information indicating the quantization level may determine the feedback payload size for the side information.

[0159] The WTRU may be configured with a threshold for the reporting of the differential CSI. The WTRU may use the threshold to decide on the reporting of (e.g., determine whether to report) the differential CSI component in addition to low resolution codebook-based PMI.

WTRU Configuration for Multiple CSI Report

[0160] The WTRU may receive one or more CSLRS from the network and may compute the CSI parameters using the CSLRS resources. In an example, the WTRU may use the same CSLRS to compute multiple CSI parameters (e.g., low resolution precoding matrix and ideal precoding matrix). In another example, the WTRU may receive different CSLRS to compute different CSI parameters (e.g., a first set of CSLRS for low resolution precoding matrix and a second set of CSL RS for any of the legacy precoding matrix and the ideal precoding matrix). Using the one or more (set of) CSLRS received from the network, the WTRU may perform (e.g., operate) according to one or more of the following examples.

[0161] In a first example, based on one or more (set of) CSLRS received from the network, the WTRU may compute a low-resolution type I/II codebook-based precoding matrix (e.g., of smaller payload size) according to the configuration information received from the network.

[0162] In a second example, based on one or more (set of) CSLRS received from the network, the WTRU may compute the ideal precoding matrix.

[0163] In a third example, based on one or more (set of) CSLRS received from the network, the WTRU may compute more than one CQI, where a (e.g., each) CQI may correspond to a different resolution codebook-based precoding matrix. For example, a first CQI may correspond to a low- resolution codebook-based PM and a second CQI may correspond to the ideal and/or legacy precoding matrix.

[0164] In a fourth example, based on one or more (set of) CSI-RS received from the network, the WTRU may compute the difference between the codebook-based precoding matrix and the ideal precoding matrix, e.g., the differential CSI.

[0165] In a fifth example, the WTRU may be configured to compute (e.g., based on one or more (set of) CSI-RS) different resolutions of type I/II codebook-based precoding matrices, each with a different resolution, ranging from low to high. The WTRU may compute the difference between any two of those precoding matrices resulting in more than one differential CSI.

[0166] In a sixth example, the WTRU may compress one or more of the CSI parameters (e.g., any of the computed precoding matrices as described herein) using a (e.g., trained) autoencoder. The applied compression ratio may be any of (i) up to the autoencoder, (ii) pre-configured by the network, and (iii) based on an indicated payload size (which may correspond to the size of a configured grant at the WTRU).

[0167] In a seventh example, based on one or more (set of) CSI-RS received from the network, the WTRU may compute side information allowing the network to detect any mismatch between the precoder/encoder at the WTRU and the decoder/precoder at the network, for example, any of time stamps, indices pointing to the CSI-RS used to compute the CSI parameters, etc.

[0168] In an eighth example, the WTRU may receive information indicating one or more rules (e.g., configurations) for the WTRU to determine the reporting configurations. For example, for CSI report part 1, use CG configuration 1, for CSI report part 2, use CG configuration 2. Or for CSI report part 1, use the currently activated CG configuration, for CSI report part 2, request for additional resources (e.g., via SR/BSR).

[0169] In various embodiments, the parameters for differential CSI compression mechanism at the WTRU may be configured semi-statically via radio resource control (RRC), or more dynamically via MAC control element (MAC CE) and/or downlink control information (DCI) signaling. For example, any of the use of differential CSI, type of codebook for PMI, method to compute side information and threshold for differential CSI reporting may be configured via RRC. For example, more dynamic parameters such as any of (i) the payload sizes for PMI and differential CSI feedback and (ii) quantization level may be configured via MAC CE and/or DCI.

WTRU Methods for Differential CSI Compression

[0170] Example methods for differential compression at the WTRU are described herein.

Triggering for Differential CSI Compression

[0171] The WTRU may be triggered for differential CSI compression according to the received configuration information. The WTRU may start the differential CSI compression mechanism after receiving an indication from the NW via any of DCI, MAC CE and RRC signaling. The WTRU may be configured to compute and report differential CSI any of periodically, semi- periodically and a-periodically.

Computing Codebook-based PM and Ideal PM

[0172] The WTRU may receive RS resources (e.g., any of CSI-RS, synchronization signal block (SSB), etc.) to measure the channel. The WTRU may compute a low resolution (e.g., low payload size) codebook-based precoding matrix (PM), referred to herein as W_PMI. The computed precoding matrix, W_PMI may be represented with a pre-defined precoding matrix indicator (PMI) which may be aligned between the WTRU and the NW.

[0173] The WTRU may compute the ideal precoding matrix, referred to herein as Wj_DE, using the received RS resources for channel measurement. For example, the ideal precoding matrix may be computed by obtaining the eigenvectors of a function of the channel matrix or the by using singular value decomposition (SVD) of the channel matrix. For example, the ideal precoding matrix, Wj_DE, may be selected from a high-resolution codebook-based precoding matrix computation scheme.

[0174] For example, the codebook-based PM may represent the PM for a wideband channel. In this case, the differential PM may be computed such that it may represent the difference of a codebook-based (e.g., wideband) channel PM and ideal (e.g., sub-band) channel PM.

Differential Precoding Matrix and its Compression

[0175] In various embodiments, the WTRU may compute the low-resolution codebook-based PM, Wp_Mj, and the ideal PM, Wj_DE. The WTRU may compute a matrix representing the difference between the two precoding matrices, W_Diff (e.g., differential precoding matrix). In an example, the differencing may be based on a subtraction such that W_Diff = W_PMI — Wj_DE. In another example, the differencing between the two matrices may be based on an invertible differencing function such that W_Diff = oiffC^PMi ^— ^IDE)-

[0176] In various embodiments, the WTRU may use a (e.g., pre-trained) autoencoder to compress the differential precoding matrix, W_Diff. Considering that the differential PM may be the difference between a low-resolution PM and an ideal PM computed for the same channel measurement, the differential PM may become sparse, such that the compression ratio of the differential PM may be higher than the compression ratio of the ideal PM. This may lead to lower payload. The WTRU may compress the differential PM and may obtain _e(W_Diff), where _e(-) may be referred to as the encoder neural network (NN) of AE.

Computing the Side Information to Detect Mismatch [0177] In various embodiments, the WTRU may compute side information, s_Diff, for the NW to detect mismatch at the output of the decoder NN of autoencoder. As an example, the side information may comprise any of (i) the norm of the differential PM such that s_Diff = || W_Diff || , (ii) the ratio of magnitudes of differential PM and codebook-based PM, such that s_Diff = !!^Wpiff* and

IIWpMI II

(iii) the SGCS distance between ideal PM Wj_DE and codebook-based PM W_PMb such that s_Diff =

[0178] The side information s_Diff may comprise a scalar value and may be quantized to be represented with a fewer number of bits to save payload size.

[0179] FIG. 4 is a diagram illustrating an example procedure for differential CSI compression and feedback. A differencing operation 41 may be applied to a low-resolution precoding matrix and an ideal precoding matrix to obtain a differential precoding matrix. As shown at 42, side information to detect mismatch may be obtained based on the low-resolution precoding matrix and the differential precoding matrix. An AE-based compression 43 may be applied to the differential precoding matrix to obtain a compressed differential precoding matrix. The WTRU may feedback to the NW any of the low-resolution precoding matrix, the side information and the compressed differential precoding matrix.

Omitting the Differential PM

[0180] The differential PM that may be computed by differencing the ideal PM and codebookbased PM may be negligible depending on the channel realizations. In case, the magnitude of the differential PM, ||W_Diff||, is below the (e.g., configured) threshold, then the WTRU may omit reporting the compressed differential PM, _e(W_Diff). In case the WTRU does not report the compressed differential PM, the WTRU may notify the NW (e.g., transmit information indicating to the network absence of the differential PM).

WTRU Feedback for Mismatch Detection and Differential CSI Compression

[0181] In various embodiments, the WTRU may feedback the low-resolution codebook-based PM W_PMi using a legacy precoding matrix indicator (PMI). The feedback on (e.g., associated with) PMI may occupy a payload size that may have been indicated from the NW.

[0182] In various embodiments, the WTRU may feedback the compressed differential PM /_e(W_Diff). The feedback on (e.g., associated with) compressed differential PM may occupy a payload size that may have been indicated from the NW.

[0183] In various embodiments, the WTRU may report the side information for mismatch detection s_Diff. The side information may comprise a quantized representation of the scalar value s_Djff, quantized based on any of a pre-configuration and an indication from NW. [0184] In various embodiments, the WTRU may omit the reporting of the compressed differential PM if a condition is satisfied. In case, the WTRU does not report the compressed differential PM, a reserved one-bit field in the feedback may be set to notify the NW that the compressed differential PM is not included in the current CSI report. Any other method for indicating absence of report data may be applicable to embodiments described herein.

[0185] In various embodiments, the WTRU may send the feedback over uplink channels as indicated by the NW, such as in any of PUCCH and PUSCH (e.g., resources).

Reporting of the CSI report(s) to the network

[0186] The WTRU may be configured with multiple resources and/or types thereof and configurations and/or types thereof to transmit the CSI report(s) or parts thereof to the network. For example, the WTRU may be configured with one or more configured grant configurations and/or send a request for dynamic grants (e.g., via SR/BSR). The WTRU may be configured to determine the priority of the CSI report (or part thereof) and may select any of the resources and the resource types to transmit to the network accordingly. For example, the WTRU may transmit the higher priority report via the next available grant (e.g., granted resource), such as e.g., any of the next available CG or dynamic grant in response to a request for resources sent to the network. In another example, the WTRU may receive indication on the resources and/or type thereof to use to send the CSI reports (or part thereof) on a case-by-case basis. For example, the reception of the differential CSI request 1 from the NW may also indicate the time and frequency resources to be used for the corresponding feedback (e.g., CSI report part 1).

[0187] In an example, the WTRU may report (e.g., all) the CSI parameters computed from the same CSI-RS at once (e.g., in a same report), for example, the two CQIs and/or the different precoding matrices (e.g., ideal precoding matrix, low resolution precoding matrix, etc.) may be reported in a same report information transmission. In another example, the WTRU may report the CSI parameters in stages, e.g., in different resources/resource configurations (e.g., in different transmissions). For example, the WTRU may receive a differential CSI request 1 from the NW that may indicate resources to be used for the feedback. In response, the WTRU may send back CSI Report Part 1 including, for example, the PMI and two CQI values (e.g., corresponding to codebook based PM and ideal PM). The WTRU may then receive a differential CSI Request 2 from the network, for example, based on the decision given by the network considering the two CQIs. The request may indicate any of PUSCH and PUCCH resources to be used for feedback. In response, the WTRU may feedback a CSI Report Part 2 including, for example, the compressed differential PM and mismatch metric. Whether the WTRU reports the CSI parameters at once or in stages may depend (e.g., be based) on the available resources and/or resource configurations at the WTRU. WTRU Sending Scheduling Request (SR) to the Network

[0188] The WTRU may send a request to the network requesting for resources, for example, if the WTRU has data in its buffer (e.g., one or multiple CSI reports or parts thereof) with no available or insufficiently available grants (e.g., resources) to use to transmit the reports.

[0189] In an embodiment, the WTRU may send a scheduling request (SR) to request for an uplink grant (e.g., scheduling one or more resources) to send the different parts of the CSI reports to the network (e.g., over the PUS CH).

[0190] In one example, the SR may be transmitted on a PUCCH. In another example, the SR may be transmitted on the uplink control information (UCI) part of a PUSCH.

[0191] In one example, the SR may be a legacy SR (e.g., with parameters such as SR configuration index, SR PUCCH resource index, etc.). In another example, the SR may include additional information associated with the CSI reports or parts thereof to report, e.g., indicating any of a size, a timing, priority levels of part 1 CSI report, part 2 CSI report and so forth.

[0192] In response to the SR, the WTRU may receive an uplink grant (e.g., scheduling information) from the network (e.g., in DCI 0 0 / DCI 0 1), e.g., via physical downlink control channel (PDCCH). In an example, the WTRU may be configured with rules and/or criteria from the network on the data to include in (e.g., resource(s) scheduled by) an UL grant as a response to an SR (e.g., use the grant to send CSI report part 1 or the highest priority segment of the CSI report).

[0193] In one example, the WTRU may (e.g., only) be able to send an SR to the network if there is no other SR in progress. In another example, the WTRU may be configured with a (e.g., maximum) number of SR that may be transmitted concurrently. If the configured (e.g., maximum) number of SR has not been reached, the WTRU may transmit an SR to the network in presence of another ongoing SR. In yet another example, there may not be any restrictions on the number of SRs that the WTRU may be allowed to send to the network (if the WTRU has data in its buffer and no available grant via which to transmit the data). The WTRU may send an SR to the network. [0194] In one example, the WTRU may not be configured to transmit SR (e.g., the PUCCH for SR may not be configured), in which case the WTRU may initiate a random-access channel (RACH) process to get (e.g., ask) the network to configure the timing and/or physical control channel resources for SR transmission (e.g., in a RRC connection setup message).

[0195] In one example, if the WTRU does not receive any UL grant information in response to the SR, the WTRU may send SR several more times to the network (e.g., if there is no available grant to transmit the data in its buffer). Failure to obtain resources may trigger the WTRU to initiate RACH process and reconfigure the SR configurations.

WTRU sending Buffer Status Report (BSR) Information to the Network [0196] In a first transmission of an SR, the WTRU may (e.g., only) indicate to the network that the WTRU may have data to transmit and that the WTRU may request the network to schedule resource blocks (RBs) for the transmission, e.g., without providing any information on the data in the WTRU buffer. In a BSR, the WTRU may be able to provide additional information on any of the data in the WTRU buffer and the upcoming data in the WTRU buffer.

[0197] In an example, the WTRU may send an SR (e.g., on PUCCH) and may be granted resources (e.g., on PUSCH). The WTRU may use the grant (e.g., granted resources) to send a BSR to the network to inform the network of any of the following indications.

[0198] A BSR may indicate any of an amount, a size and a volume of data available in WTRU buffer.

[0199] A BSR may indicate a type of data in the WTRU buffer, such as e.g., any of CSI report, CSI report part 1, CSI report part 2, etc.

[0200] A BSR may indicate components/content of data in the WTRU buffer and their corresponding size (e.g., volume). For example, components/content of data may include any of precoding matrix, low-resolution codebook-based PM, CQI for low-resolution codebook-based PM, ideal precoding matrix, difference between codebook-based precoding matrix and ideal precoding matrix, associated with their corresponding size (e.g., volume).

[0201] A BSR may indicate a priority of CSI report or part thereof. In one example, if the WTRU detects that the radio conditions do not satisfy a quality condition e.g., based on measurements made by the WTRU, the WTRU may prioritize transmitting the CSI report over other data. If the network is not able to provide sufficient grants to accommodate (e.g., all) the data in the WTRU buffer (e.g., due to any of congestion, overloading, etc.), it may schedule a grant to (e.g., only) send the CSI report. The network may also send an indication to the WTRU to use the limited grant to send the CSI report (e.g., prioritizing it over other data currently/incoming in the WTRU buffer). In another example, CSI report part 1 may be of higher priority than CSI report part 2, e.g., depending on the components.

[0202] A BSR may include time information, such as e.g., any of a time to transmit the CSI parameters, a remaining time by which the CSI parameters may be transmitted, etc.

[0203] A BSR may include reference information, such as e.g., any of a CSI report part 1 corresponding to differential CSI request 1, a CSI report part 2 corresponding to differential CSI request 2, etc.

[0204] In an example, the WTRU may send one BSR to request for resources to transmit one CSI report.

[0205] In an example, the WTRU may send one BSR to request for resources to transmit a part of a CSI report. [0206] In an example, the WTRU may send one B SR to request for resources to transmit multiple CSI reports corresponding to different differential CSI requests or multiple parts of a CSI report, each corresponding to a different type of differential CSI report, e.g., based on the request from the network. For example, in one BSR report, the WTRU may report the total (expected) volume of the multiple CSI reports or parts thereof.

[0207] In an example, the WTRU may send short BSR format (e.g., if the WTRU has a smaller amount of data).

[0208] In another example, the WTRU may send a long BSR format. In a first example, the long BSR may be similar to the legacy BSR where the WTRU may have a larger volume of data and/or data associated with more than one logical channel group (LCG). In response, the WTRU may receive a grant from the network. In a second example, the long BSR may allow the WTRU to request for more than one grant, e.g., the WTRU may report two indices via the BSR corresponding to the size (e.g., volume) of two grants that the WTRU may receive from the network. The WTRU may use each grant for a CSI report or part thereof. The WTRU may receive the two grants from the network together or at an offset from each other.

WTRU Configured with Configured Scheduling

[0209] The WTRU may be configured with one or more CG (Configured Grant) configurations. [0210] In one example, the parameters of the one or more CG configurations (such as e.g., any of the periodicity, start offset, grant size, etc.) may be configured by the network based on the CSI reporting expectations of the WTRU (e.g., number of CSI reports or parts thereof, size and/or content and/or priority of CSI reports or parts thereof, etc.).

[0211] In one example, the semi-static configured scheduling may be configured in RRC (e.g., using a rrc-ConfiguredUplinkGrant message) and may be activated (e.g., without any trigger). The WTRU may be configured with the resources (e.g., PUSCH) and the periodicity, such that the grants may be used by the WTRU to send the CSI reports or parts thereof.

[0212] In another example, the semi-static configured scheduling may be activated based on trigger information from the network (such as e.g., DCI via PDCCH). The WTRU may receive the trigger information standalone (e.g., in DCI) and/or together with (e.g., included in) another message (such as e.g., any of a differential CSI request, a differential CSI request part 1, a CSI-RS resources, etc.) received from the network.

[0213] In one example the WTRU may be configured with multiple CG configurations, where different (e.g., each) CG configurations may have different parameters (e.g., any of start offset, periodicity, grant size, etc.). In one example, the parameters for one CG config may be configured to align with one type of CSI report (e.g., the grant size and start offset of CG config 1 may be aligned with the data size and reporting periodicity of CSI report part 1; the grant size and start offset of CG config 2 may be aligned with the data size and reporting periodicity of CSI report part 2, etc.). With a (e.g., each) CG configuration tagged to a type of CSI report or part thereof, the WTRU may not label the CSI report or part thereof.

Methods at the Receiving Network Element for Differential CSI Decompression

[0214] The WTRU may send feedback on any of the low-resolution PM W_PMb the compressed differential PM _e(W_Diff) and the side information to detect mismatch s_Diff to the receiving network element (e.g., NW or another WTRU). The feedback on low-resolution PM W_PMj and s_Diff may be (e.g., perfectly) recovered at the NW based on no residual transmission errors. The reconstruction of W_Diff may be subject to lossy decompression (e.g., even based on no residual transmission errors).

[0215] FIG. 5 is a diagram illustrating an example procedure at the NW-side for differential CSI compression. As shown at 51, the NW may reconstruct (e.g., decompress) the differential PM, such that W_Diff = _d( _e(W_PMi — Wj_DE)), where _d(-) may refer to the decoder NN of AE. The reconstructed differential PM W_Diff may be the decompressed approximation of the W_Diff computed at the WTRU. A (e.g., significant) difference in W_Diff and W_Diff may lead to detection of mismatch.

[0216] As shown at 52, the NW may reconstruct the ideal PM by combining low-resolution codebook-based PM and decompressed differential CSI, such that Wj_DE = W_PMj + W_Diff. The reconstructed ideal PM Wj_DE may approximate the ideal PM Wj_DE computed at the WTRU.

[0217] The NW may perform mismatch detection 53 based on the side information s_Diff sent by the WTRU. The NW may process any of the side information s_Diff, the low-resolution PM W_PMI sent by the WTRU and the reconstructed differential PM W_Diff to obtain a processed side information, referred to as s_Diff. As an example, the NW may detect mismatch based on any of the following variants.

[0218] In a first variant, the NW may compute the norm of the reconstructed differential PM such that s_Diff = ||W_Diff||.

[0219] In a second variant, the NW may compute the ratio of magnitudes of reconstructed differential PM and codebook-based PM, such that s_Diff =

II WpMi ||

[0220] In a third variant, the NW may compute the SGCS distance between the reconstructed ideal PM W_IDE and codebook-based PM W_PMb such that s_Diff =

, I vv _vv ll^WIDE-^WPMl||

-S_GCAVV_IDE, VV_PMIJ ||W_IDE||₂I|W_PMI||₂’

[0221] The NW may compare s_Diff and s_Diff, and if the difference between the two values is above a threshold, then the NW detects a mismatch. In case the NW detects a mismatch, the NW may use the codebook-based PM W_PMb otherwise, the NW may use the reconstructed ideal PM WIDE-

Example of Differential CSI Compression and Feedback on Mismatch Detection

[0222] In an embodiment, a WTRU may determine (e.g., compute) compressed differential CSI based on the difference between ideal CSI and low-resolution codebook-based CSI. The WTRU may report any of compressed differential CSI, PMI and mismatch metric.

[0223] In a first step, the WTRU may receive configuration information on differential CSI compression indicating any of (a) the payload size low-resolution precoder matrix (PM) feedback (e.g., Type I/II PMI feedback), (b) the payload size of differential CSI compression, (c) an indication on the use of differential CSI compression, (d) any of uplink resources and resource types for different parts of CSI report, and (e) rules (e.g., configurations) for the WTRU to determine the reporting configurations (e.g., for CSI report part 1, use configured grant (CG) configuration 1, for CSI report part 2, use CG configuration 2. Or for CSI report part 1, use the currently activated CG configuration, for CSI report part 2, request for additional resources (e.g., via any of scheduling request (SR) and buffer status report (BSR)).

[0224] In a second step, the WTRU may receive a CSI reference signal (RS) and may determine (e.g., compute) the differential CSI.

[0225] For example, the WTRU may determine (e.g., compute) a low-resolution (e.g., low payload size) Type I/II codebook-based precoding matrix (PM) according to the indicated configuration based on CSI-RS measurements. The low-resolution PM may correspond to a wideband channel.

[0226] For example, the WTRU may determine (e.g., compute) one or more ideal precoding matrix(ces) based on CSI-RS measurements. The ideal PM may correspond to a sub-band channel. [0227] For example, the WTRU may determine (e.g., compute) two channel quality indicators (CQIs): CQI l for low resolution codebook-based PM and CQI 2 for ideal PM.

[0228] For example, the WTRU may determine (e.g., compute) the one or more difference of codebook-based precoding matrix and ideal precoding matrix, e.g., the differential CSI (e.g., one per sub-band).

[0229] For example, the WTRU may compress the one or more differential CSI (e.g., using a trained AE) based on the indicated payload size.

[0230] For example, the WTRU may determine (e.g., compute) one or more side information(s) for the detection of mismatch at NW side.

[0231] In a third step, the WTRU may determine the feedback.

[0232] In a case where the WTRU reports one CSI report based on configuration, the WTRU may report the low-resolution PM and one or more compressed differential CSI. The WTRU may 30 report the one or more side information(s) for mismatch detection. The WTRU may report one or more CQI values. The WTRU may report (e.g., only) the low-resolution PM if the difference between codebook based PM and ideal PM is low (e.g., is lower than a threshold).

[0233] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may receive (e.g., information indicating a) differential CSI request 1 from the NW that may indicate resources to be used for the feedback. The WTRU may determine priorities for different CSI reports, e.g., based on any of available uplink resources, channel conditions, etc. The WTRU may determine to report CSI Report 1 on next available uplink grant based on the determined priorities of the two CSI reports.

[0234] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may feedback CSI Report Part 1 including any of PMI and two CQI values, mismatch metric (corresponding to codebook based PM and ideal PM).

[0235] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may receive (e.g., information indicating a) differential CSI request 2 from the NW, (e.g., based on the decision given by NW considering the two CQIs). The request (e.g., information) may indicate any of PUSCH and PUCCH resources to be used for feedback.

[0236] In a case where the WTRU reports more than one CSI reports based on configuration, the WTRU may feedback CSI report Part 2 including any of the one or more compressed differential PM and one or more side information on mismatch metric.

[0237] In a fourth step, the WTRU may receive data precoded with codebook-based low- resolution PM or reconstructed ideal PM.

WTRU Determining and Reporting the Parameters of Differential CSI Compression

[0238] An example method for determine and reporting by a WTRU the parameters of differential CSI compression is described herein.

WTRU Configuration for Determining the Parameters of Differential CSI Compression

[0239] A WTRU may report CSI using differential CSI approach. Differential CSI report information may include (e.g., indicate) any of (i) a low-resolution PM, (ii) a differential PM (e.g., the difference between the low-resolution PM and a calculated ideal PM), (iii) a compressed differential PM (e.g., compressed using an AI/ML model encoder at the WTRU), (iv) an ideal PM and (v) side information (e.g., a value determined from a low-resolution PM and an uncompressed differential PM).

[0240] A WTRU may be configured with one or more parameters to report CSI to the gNB. The one or more parameters may include (e.g., indicate) any of (i) feedback component types to report, (ii) timing of feedback reports, (iii) payload size(s), (iv) a ratio of total payload per feedback component type, (v) a low-resolution PM type, (vi) a type of side information, (vii) a granularity of a feedback report type, (viii) a quantization to use for a feedback report type, (ix) a performance criterion of a feedback report type, (x) an UL transmission power, and (xi) an indication of whether to allow UCI on PUSCH or to use PUSCH-PUCCH transmissions.

[0241] Related to the parameter indicating feedback component types to report, a WTRU may report, for example any of a low-resolution precoding matrix (PM) (e.g., PMI), a differential PM, a compressed differential PM, side information (e.g., for mismatch detection), a total payload size, a payload size for a configured feedback component type.

[0242] Related to timing parameter of feedback reports, the WTRU may be configured with, for example, a specific time or slot to transmit a report (e.g., aperiodic reporting). In another example, the WTRU may be configured with any of a periodicity, an offset, a start time, and an end time to transmit a report (e.g., periodic or semi-persistent reporting). The timing of a feedback report may be associated to one or more of the feedback component types. For example, a first feedback component type may be configured with a first reporting periodicity and offset, and a second feedback component type may be configured with a second reporting periodicity and offset.

[0243] Related to the payload size(s) parameter, which may include any of a maximum, a minimum and a fixed payload size, for example, a feedback component type may be configured with, for example, any of a maximum, minimum and fixed payload size. In another example, the total feedback report may be configured with any of a maximum, minimum and fixed payload size. [0244] Related to the parameter indicating a ratio of total payload per feedback component type, a ratio (e.g., any of a maximum, minimum and fixed ratio) of the total report payload size may be assigned, for example, to a (e.g., each) feedback component type in a feedback report. For example, a feedback report may be configured with a maximum value P (P being an integer value) and in an instance the feedback report may include low-resolution PM feedback report type and compressed differential PM feedback report type. The low-resolution PM feedback report type may be configured with a maximum ratio of x (0<x<l), such that in a feedback report of size P, the low-resolution feedback may have maximum payload size of xP.

[0245] Related to the low-resolution PM type parameter, a WTRU may be configured with one or more low-resolution PM types. The low-resolution PM types may include any of: (i) codebookbased reporting (e.g., WTRU-determined and indicated codebook or pre-configured codebook), (ii) eigenvalue-based reporting (compressed or uncompressed), (iii) subset of eigenvector reporting (e.g., eigenvector associated with a specific eigenvalue, such as max eigenvalue), (iv) a matrix rank. In an example, a WTRU may be configured with multiple PM codebooks for low- resolution PM. The WTRU may select one of the PM codebooks for a report such that a feedback report may satisfy one of the other parameters described herein (e.g., payload size). In an example, a WTRU may be configured with different CSI reporting parameters for a (e.g., each) configured low-resolution PM type.

[0246] Related to the type of side information parameter, a WTRU may be configured with one or more types of side information. The WTRU may select one of the types of side information for a feedback report such that the feedback report may satisfy one of the other parameters described herein (e.g., payload size). In an example, a WTRU may be configured with different CSI reporting parameters for different (e.g., each) configured side information type.

[0247] Related to the parameter indicating a quality or performance criterion of a feedback report type, the WTRU may be configured with, for example, multiple levels of quality of differential PM. The WTRU may determine a quality or performance criterion based on another parameter to report CSI and/or based on a performance of CSI feedback.

[0248] The WTRU may determine any of the timing of a feedback report, the content of the feedback report, the report resource to use, and the priority of a feedback report based on one or more of the parameters described above.

[0249] In an embodiment, a WTRU may be configured with the feedback report types to use to determine the side information. For example, the WTRU may be configured with reference time (e.g., measurement time or report time) of a (e.g., each of the) feedback report types to be used to determine the side information to be reported at a (e.g., specific) time.

[0250] A WTRU may determine the payload of one or more feedback component types in a feedback report, or the payload of the feedback report. The WTRU may transmit information to the gNB indicating the determined payload(s). The information may be transmitted in any of the feedback report resource and a dedicated payload indication transmission resource. The information may use, for example, a fixed set of bits in a feedback report to enable decoding of the remaining bits of the feedback report.

[0251] In various embodiments, the WTRU may be configured semi-statically via RRC, or more dynamically via MAC CE and/or DCI signaling to determine the parameters for differential CSI compression.

WTRU Determining the Parameters of Differential CSI Compression

[0252] A WTRU may be configured with one or more reference signal resources to determine the parameters of a CSI feedback report, for example, using differential CSI compression. The one or more reference signal resources may be the same or different or partially overlap those used to determine the CSI.

[0253] From one or more set(s) of reference signals (e.g., CSI-RS), the WTRU may calculate a channel matrix. From the ideal channel matrix, the WTRU may determine an ideal precoding matrix (ideal PM). Based on any of the above CSI reporting parameters and/or the ideal PM, the WTRU may determine one or more payload values or sizes (e.g., optimal payload value or size) for a (e.g., each of the) reported feedback component types. The determination may be done based on any of: (i) a table of (e.g., allowed) values, (ii) a use of a decoder/decompressor (e.g., a proxy decoder/decompressor) at the WTRU, (iii) a performance metric calculation and (iv) a feedback report type.

[0254] Related to the determination based on a table of (e.g., allowed) values, for example, the WTRU may be configured with a set of possible payload values, where a (e.g., each) payload value may be associated with one or more parameters obtained from an ideal channel matrix or ideal PM.

[0255] Related to the determination based on the use of a decoder/decompressor (e.g., a proxy decoder/decompressor) at the WTRU, for example, the WTRU may be configured with an encoder/compressor and a decoder/decompressor. The WTRU may determine a payload value for at least one of the reported feedback component types based on the performance of the encoder/decoder (or compressor/decompressor) pair.

[0256] Related to the determination based on the performance metric calculation, for example, the payload value for at least one of the reported feedback component types may be determined such that a performance metric of the feedback may satisfy a criterion (e.g., compared to a configurable threshold). In an example, the WTRU may determine any of the minimum and maximum payload to satisfy a (e.g., specific) performance metric. The performance metric of the feedback may be determined based on any of the following examples.

[0257] In a first example, the performance metric of the feedback may be determined based on an SGCS between any two of: low-resolution PM, ideal PM, reconstructed ideal PM. For example, the payload may be determined as the (e.g., minimum, lower) payload value for which the SGCS may be less than a threshold. For example, the WTRU may be configured with a decompressor and may determine the reconstructed ideal PM from any of the decompressor output, the low- resolution feedback, and the side information.

[0258] In a second example, the performance metric of the feedback may be determined based on a distance metric between any two of: low-resolution PM, ideal PM, reconstructed ideal PM.

[0259] In a third example, the performance metric of the feedback may be determined based on a minimization of side information value.

[0260] In a fourth example, the performance metric of the feedback may be determined based on a minimization of payload of at least one reported feedback type or for over-all feedback report.

[0261] Related to the determination (of one or more payload values or sizes) based on the feedback report type, for example, the payload may be determined based on the low-resolution PM type used. In another example, the payload for one or more feedback report types may be determined based on the set of feedback report types to be reported in a reporting instance.

[0262] In various embodiments, the WTRU may report one or more payload values (for one or more reported feedback types). In an embodiment, the WTRU may be configured with a set of (e.g., possible) payload values and may report one or more payload value index; where a (e.g., each) payload value index may be associated with a configured (e.g., possible) payload value.

[0263] The WTRU may determine (e.g., select) one or more of the parameters described herein to report CSI. The determination may be based on any of a calculated channel matrix, an ideal precoding matrix, a feedback resource (or parameter thereof, such as payload size), a timing of the feedback report, a performance of an associated transmission (e.g., hybrid automatic repeat request acknowledgment (HARQ-ACK) performance or block error rate (BLER)), and a priority of a feedback report.

[0264] Any methods described herein for the determination of payload value(s) may be reused for the determination of other parameters to report CSI. For example, the WTRU may select a low- resolution PM satisfying a (e.g., specific) performance metric criterion.

[0265] The determination (of one or more of the parameters described herein to report CSI) may be based on the determined payload. For example, the WTRU may first determine the payload for one or more reported feedback types and based on the determined payload value(s), the WTRU may determine the reported feedback types to report in a reporting instance.

[0266] The determination (of one or more of the parameters described herein to report CSI) may be based on any of (i) the timing of the feedback report, (ii) a transmit receive point (TRP) associated with the feedback report, (iii) a beam associated with the feedback report, (iv) a RS associated with the feedback report, (v) whether a feedback report is triggered a-periodically, is periodic or is semi-persistent and (vi) the trigger or trigger type or measurement used to trigger an aperiodic report.

[0267] The determination (of one or more of the parameters described herein to report CSI) may be based on any of an UL transmission power and a feedback report channel. For example, the WTRU may determine a parameter based on any of the scheduled UL transmission power, the available power, and the power headroom. For example, a parameter of CSI feedback may be determined based on whether a feedback report is in PUCCH or PUSCH.

[0268] In an embodiment, a WTRU may determine a first payload for a first feedback report type and based on the performance associated with the first payload and the first feedback report type, the WTRU may determine a second payload for a second feedback report type. For example, a WTRU may determine a payload value for low-resolution PM reporting. Based on the performance of the low-resolution PM (where the performance may be determined by a performance metric as described herein), the WTRU may determine a payload for a compressed differential PM report type. For example, if the WTRU determines that the low-resolution PM provides a performance satisfying a condition based on a metric (e.g., distance between the low-resolution PM and the ideal PM), the WTRU may determine to not provide any payload for compressed differential PM (e.g., the WTRU may determine to not report compressed differential PM).

[0269] In an embodiment, a WTRU may be configured with multiple differential PM encoders or compressors (e.g., multiple AI/ML models to use for encoding differential PM). The WTRU may select a differential PM encoder/compressor based on any of (i) the determined payload of the compressed differential PM, or low-resolution PM or side information, (ii) the determined quality or performance of the compressed differential PM, and (iii) the performance metric. For example, the performance metric may be determined based on a calculated side information value. For example, the WTRU may select a differential PM encoder/compressor that may minimize a side information value. In another example, the performance metric may be based on minimizing any of an SGCS and a distance metric.

[0270] In an embodiment, the WTRU may determine one or more parameters of UL transmission power as a function of the parameters of CSI feedback. For example, the UL transmission power may be determined based on any of: (i) the one or more payload values of the one or more reported feedback types, (ii) the set of reported feedback types, (iii) the priority of the feedback report, and (iv) the encoder/compressor used. For example, if any of the indicated and selected autoencoder is trained (e.g., also) for noise and/or error suppression then the UL transmission power for the associated UL transmission may be decreased. In another example, if any of the indicated and selected autoencoder is known to be sensitive to any of noise and error, then the UL transmission power may be increased.

WTRU Reporting Parameters of Differential CSI Compression

[0271] A WTRU may report a WTRU-determined or WTRU-selected CSI reporting parameter to the gNB. For example, the WTRU may report one or more payload value(s) for one or more feedback report types.

[0272] In an example, the WTRU may report a CSI reporting parameter in a (e.g., every) CSI feedback report. In another example, the WTRU may be configured to report a CSI reporting parameter in (e.g., specific) CSI feedback reports, and/or at (e.g., specific) times. For example, a WTRU may report the payload values for one or more feedback report types periodically. The WTRU may report any other CSI feedback report type using the payload values most recently reported by the WTRU. [0273] In yet another example, a WTRU-determined or WTRU-selected CSI reporting parameter may be a dedicated feedback report type. In such a case, the WTRU may report the WTRU- determined or WTRU-selected CSI reporting parameter in feedback instances where such a feedback report type may be configured to be included.

[0274] The WTRU may report a CSI reporting parameter in a case where there is a change in the parameter. For example, if the type of low-resolution PM changes, the WTRU may include an indication of the change or an indication of the low-resolution PM (e.g., the newly determined or selected low-resolution PM).

[0275] A WTRU may request a WTRU-determined or WTRU-selected CSI reporting parameter and may wait for an acknowledgement from the gNB before using the requested CSI reporting parameter in a CSI report.

[0276] A WTRU may determine or be configured with priority values associated with one or more (e.g., all) CSI feedback report types. For example, a low-resolution PM may be of high priority and a differential PM value may be of low priority. The priority may be used in cases where some portion of a CSI report may be dropped or multiplexed with another transmission. The priority of a feedback report type may be determined as a function of the set of feedback report types in a feedback report instance. For example, if a feedback report includes a low-resolution PM and a compressed differential PM, the priority of a compressed differential PM may be low; if a feedback report does not include a low-resolution PM and (e.g., only) includes a compressed differential PM, the priority of the compressed differential PM may be high. Switching the priority of a compressed differential PM to high in a case where the feedback reports do not include any low-resolution PM may allow the compressed differential PM to not be dropped (e.g., when contending with other transmissions of lower priorities) such as to improve the reception at the gNB in absence of low-resolution PM.

Example of Determining and Reporting the Parameters of Differential CSI Compression

[0277] In an embodiment, a WTRU may determine the parameters of differential CSI compression as a function of any of (e.g., total) payload size and channel conditions. The WTRU may report the determined parameters.

[0278] In a first step, the WTRU may receive configuration information on differential CSI indicating any of (a) the total payload size of CSI report, (b), an indication on the use of differential CSI compression and (c) an indication on the WTRU to determine and report low resolution PMI and differential CSI compression parameters.

[0279] In a second step, the WTRU may receive CSI-RS and may determine (e.g., compute) the differential CSI. [0280] For example, the WTRU may determine (e.g., compute) an ideal precoding matrix based on CSI-RS measurements.

[0281] For example, the WTRU may determine the parameters (e.g., any of payload sizes, type of side information, code-book type for PMI) for low resolution PM and differential CSI compression, based on any of (i) a table of (e.g., allowed) values, (ii) a use of a decoder/decompressor (e.g., a proxy decoder/decompressor), (iii) a performance metric calculation (e.g., squared generalized cosine similarity (SGCS), minimum payload size), and (iv) a feedback report type.

[0282] For example, the WTRU may determine (e.g., compute) the codebook-based precoding matrix based on determined parameters.

[0283] For example, the WTRU may determine (e.g., compute) the difference of codebook-based precoding matrix and ideal precoding matrix, e.g., the differential CSI.

[0284] For example, the WTRU may compress the differential CSI using (e.g., an AE-based) compression based on the determined parameters.

[0285] For example, the WTRU may determine (e.g., compute) side information based on the determined parameters for the detection of mismatch at NW side.

[0286] In a third step, the WTRU may report any of (a) the determined parameters (e.g., any of payload sizes, type of side information, code-book type for PMI) for differential CSI compression, (b) the low-resolution PM and compressed differential PM, and (iii) the side information (e.g., for mismatch detection).

Windowed Differential CSI Compression

[0287] The type of CSI reported by the WTRU to the network may be referred to herein as CSI feedback type, where the CSI feedback type may be any of codebook-based precoding matrix (e.g., Type I / Type II codebook), and compressed differential CSI. The terms “Compressed differential CSI” and “differential CSI compression” may be used interchangeably in embodiments described herein. For the sake of simplicity, the expression “reporting a first/second CSI feedback type” may be used to refer to “reporting a first/second CSI feedback of a first/second type” and may be used interchangeably with “reporting a first/second CSI feedback of a first/second CSI feedback type”. [0288] FIG. 6 is a diagram illustrating an example of windowed differential CSI compression. For CSI feedback reporting, a windowed differential CSI compression mode of operation may be used, wherein a first temporal CSI report in a window 61 may be based on the first temporal CSI- RS reference resource and may comprise two CSI feedback types 611 612, and the second, subsequent CSI report in the window may comprise a single CSI feedback type 613 (e.g., compressed differential CSI). As shown in FIG. 6, the blocks labelled W_PMI 601 are examples of a first CSI report type (e.g., codebook-based precoding matrix), and the blocks labelled _e(W_Diff) 602 are examples of a second CSI report type (e.g., compressed differential CSI).

[0289] In embodiments described herein, the terms "windowed differential CSI compression mode" and "windowed mode" may be used interchangeably.

WTRU Configuration for Windowed Differential CSI Compression

[0290] A WTRU capable of performing CSI compression (e.g., using a two-sided AI/ML model), may be configured to use a windowed differential CSI compression mode.

[0291] The configuration may include a configuration for the differential CSI compression: for example, the WTRU may be configured to compress the difference matrix, or to compress the dominant eigenvectors of the difference matrix.

[0292] The configuration may include a CSI-RS configuration.

[0293] The configuration may include a window selection mode for CSI reporting, where the window selection mode may refer to how the window size may be selected, which may be any of a NW controlled window size, and a WTRU determined window size.

[0294] The configuration may include additional configuration parameters which may be a function of the window selection mode, as described herein.

[0295] The WTRU may be configured with the configuration described herein based on receiving configuration information indicating the configuration parameters described herein.

Configuration for NW controlled window size

[0296] In one example, in a case where the window size for the windowed differential CSI compression mode is controlled by the NW, the configuration of the windowed mode may include (e.g., additionally include) any of (i) a resource configuration for reporting of a first CSI feedback type, e.g., Type I/Type II or enhanced codebook, including payload size for the report, (ii) a resource configuration and payload size for reporting a second CSI feedback type, e.g., compressed differential CSI, and (iii) a window size for CSI reporting.

Configuration for WTRU determined window size

[0297] In another example, in a case where the WTRU is configured to determine the window size, the WTRU may be configured with additional parameters to enable the determination, for example, as a fraction of the channel coherence time. The WTRU may measure the channel coherence time and may determine the window size as the configured fraction of the channel coherence time. The WTRU may report the determined window size, and may receive additional configuration information of the windowed mode, such as any of (i) a resource configuration and payload size for reporting of a first CSI feedback type, e.g., type I/type II or enhanced codebook (may be a function of the WTRU reported window size), and (ii) a resource configuration and payload size for reporting a second CSI feedback type, e.g., compressed differential CSI (may be a function of the WTRU reported window size).

Windowed operation activation/deactivation

[0298] The WTRU may be configured to use a windowed differential CSI compression mode. The WTRU may activate the windowed mode, for example, in a case where the WTRU receives an activation indication from the NW (e.g., via a MAC CE). The WTRU may use the windowed mode of operation, for example, until the WTRU may receive a deactivation indication from the NW (e.g., via a MAC CE).

[0299] The parameters for windowed differential CSI compression mechanism at the WTRU may be configured semi-statically e.g., based on information received via RRC, or more dynamically based on information received via MAC CE and/or DCI signalling.

WTRU Procedures for Windowed Differential CSI Compression

[0300] A WTRU configured for windowed differential CSI compression may receive an indication to activate the windowed mode. The WTRU may select the window size for CSI reporting, based on the received configuration information (e.g., NW controlled, or WTRU determined window size). The WTRU may measure the channel response (e.g., the channel response matrix) based on the received CSI-RS.

[0301] In one example, the WTRU may determine a first CSI feedback type and a second CSI feedback type, corresponding to the first (e.g., temporal) CSI-RS received in the window, where the first CSI feedback may be a low-resolution and/or low payload size (e.g., codebook-based precoding matrix such as Type I/Type II codebook), W_PMj ₀, and the second CSI feedback may be compressed differential CSI. For the next reporting occasions in the window, the WTRU may determine to report (e.g., only) a second CSI feedback, e.g., compressed differential CSI. For example, the WTRU may determine an ideal precoding matrix or precoders from a high-resolution codebook, W_{IDE t}, based on the measured channel response at the current temporal sample t , in the window. The WTRU may determine the differential CSI at sample t within the current window, W_{Diff t}, as the difference between the first CSI feedback type determined at the beginning of the window (W_PMj ₀), and the ideal precoding matrix (or a high-resolution codebook) at the current sample

for example: W_{Diff t} = W_{PMI 0} — Wj_{DE t} where sample t may be any temporal sample within the current window (e.g., including the first sample). The WTRU may compress the differential CSI (e.g., using the WTRU-side model of an autoencoder), where the compressed differential CSI at sample t may be referred to as /_e(^Diff,t) • At sample t, the WTRU may determine side information s_Diff _t, for example, to enable the NW to detect when reconstruction mismatch of the compressed CSI may occur. The WTRU may report the compressed differential CSI at sample t, (/_e

the side information s_Diff _t. For the first sample of the window (t = 0), the WTRU may report the first CSI feedback type, e.g., W_{PMI 0}. The WTRU procedure for this example is illustrated in FIG. 7.

[0302] FIG. 7 is a diagram illustrating an example method 700 for window differential CSI compression. As shown at 710, the WTRU may measure the channel response for a current temporal sample in the window. As shown at 720, the WTRU may determine an ideal precoding matrix Wj_{DE t},. As shown at 730, it may be determined whether the current temporal sample is the first temporal sample (t=0) of the window or a subsequent temporal sample. As shown at 740, if the current temporal sample is the first temporal sample of the window, the WTRU may determine a first CSI feedback type (W_PMj ₀). As shown at 750, the WTRU may report the first CSI feedback type (W_{PMi 0}). As shown at 760, the WTRU may determine a second (e.g., differential) CSI feedback type W_{Diff t} = W_PMj ₀ — Wj_{DE t}. As shown at 770, the WTRU may determine the compressed differential CSI /_e (W_{Diff t}). As shown at 780, the WTRU may determine side information for mismatch detection s_Diff _t.. As shown at 790, the WTRU may report the compressed differential CSI and side information.

[0303] In another example (not illustrated), the WTRU may report (e.g., only) the first CSI feedback type, e.g., W_{PMI 0} at the start of the window and may report the compressed differential CSI and the side information for (e.g., all) subsequent samples in the window.

[0304] In yet another example, the WTRU may receive an indication (e.g., ACK/NACK) from the NW that the first CSI feedback type transmitted at the start of the window, e.g., W_{PMI 0}, may have been received. At the next reporting occasion, the WTRU may report the second CSI feedback type (e.g., compressed differential CSI) and the side information, for example, if the WTRU received an ACK from the NW, otherwise the WTRU may report the first CSI feedback type (e.g., the low-resolution codebook-based precoding matrix).

WTRU Reporting of Windowed Compressed Differential CSI

[0305] A WTRU configured for windowed differential CSI compression may report the determined CSI feedback in reporting information.

[0306] The reporting information may include (e.g., indicate) a first feedback type, for example, a low-resolution codebook-based precoding matrix such as Type I/Type II/enhanced Type II codebook.

[0307] The reporting information may include (e.g., indicate) a second feedback type, for example, the compressed differential CSI.

[0308] The reporting information may include (e.g., indicate) side information for determining the mismatch. [0309] The reporting information may include (e.g., indicate) a window size for CSI reporting, for example, in a case where the WTRU is configured to determine and report the window size.

[0310] The WTRU may use the first resource configuration to report the first CSI feedback type (e.g., the low-resolution CSI feedback) and may use the second resource configuration to report the second CSI feedback type (e.g., compressed differential CSI).

[0311] In one example, the WTRU may report a first feedback type only at the beginning of the window, where the first feedback type may be based on the first CSI reference resource received in the window.

[0312] In another example, the WTRU may report a first feedback type (e.g., W_PMj _t) at a later reporting opportunity in the window, for example when the previous report of W_{PMI 0} was NACK- ed (e.g., unacknowledged, or negatively acknowledged).

[0313] In one example, the WTRU may report the second CSI feedback type (e.g., compressed differential CSI), at every CSI reporting occasion within the window.

[0314] In a case where, for a CSI reporting occasion, the WTRU may report (e.g., both) a first CSI feedback type (e.g., low-resolution CSI feedback) and a second CSI feedback type (e.g., compressed differential CSI), the WTRU may use separate report resources, e.g., if configured. If (e.g., only) one resource is configured for that reporting occasion, the WTRU may prioritize reporting the first CSI feedback type.

Example of Windowed Differential CSI Compression

[0315] In an embodiment, a WTRU may determine (e.g., compute) compressed differential CSI, based on the difference between current ideal CSI and a past codebook-based CSI depending on the window size. At a (e.g., each) reporting instant, the WTRU may report compressed differential CSI and mismatch metric, and at the beginning of a reporting window, the WTRU may report a PMI.

[0316] In a first step, the WTRU may receive configuration information on differential CSI indicating any of (a) the payload size of low-resolution PM (e.g., Type I/II PMI feedback), (b) the payload size of differential CSI compression, (c) an indication on the use of differential CSI compression, and (d) an indication on the window size to report low resolution PM and differential CSI (or an indication on the WTRU to determine the window size).

[0317] In a second step, the WTRU may receive CSI-RS and may determine (e.g., compute) the differential CSI.

[0318] For example, the WTRU may select a window size based on any of an indication from the NW and the channel coherence time. [0319] For example, the WTRU may determine (e.g., compute) a low-resolution (e.g., low payload size) Type I/II codebook-based precoding matrix according to the indicated configuration (e.g., only) for the beginning of the indicated window, based on received CSI-RS.

[0320] For example, the WTRU may determine (e.g., compute) ideal precoding matrix based on one or more CSI-RS measurements.

[0321] For example, the WTRU may determine (e.g., compute) the difference of codebook-based precoding matrix (computed at the beginning of the window) and ideal precoding matrix, e.g., the windowed differential CSI, computed at a plurality of time instances within the window.

[0322] For example, the WTRU may compress the differential CSI (e.g., using a trained AE) based on the indicated payload size.

[0323] For example, the WTRU may determine (e.g., compute) a side information for the detection of mismatch at NW side.

[0324] In a third step, the WTRU may determine the feedback. The WTRU may report the low- resolution PM at the beginning of the window. The WTRU may report any of compressed differential CSI at a (e.g., every) reporting instance within the window. The WTRU may report a new low-resolution PM within a window in case of an error during the transmission of the first low resolution PM. The WTRU may report the selected window size.

[0325] In a fourth step, the WTRU may receive data precoded with codebook-based low- resolution PM or reconstructed ideal PM.

Joint Differential CSI Compression for Multi- TRP

[0326] Joint differential CSI compression methods for multi-TRP are described herein.

WTRU Configuration on Joint Differential CSI Compression for Multi-TRP

[0327] A WTRU capable of differential CSI compression may be configured (e.g., receive configuration information indicating) to use joint compression for multi-TRP. The configuration (e.g., information) may include information according to any of the following examples.

[0328] In a first example, the configuration (e.g., information) may include identification information of TRPs (e.g., indicating one or more TRPs) to be used for joint differential CSI compression. The WTRU may be configured with TRP IDs to be used for the joint differential CSI method by the NW.

[0329] In a second example, the configuration (e.g., information) may indicate the type of joint differential CSI for multi-TRP, such as e.g., any of anchor based (e.g., type) and non-anchor based (e.g., type). If a TRP is as anchor TRP then the differential CSI for (e.g., all) TRPs may be determined (e.g., computed) relative to the CSI of the anchor TRP. [0330] In case of anchor-based compression, the WTRU may be configured with (e.g., receive configuration information indicating) an anchor TRP to be used for joint differential CSI compression. In another option, the WTRU may be configured (e.g., receive configuration information indicating) to determine and report the anchor TRP to be used for joint differential CSI compression. The configuration (e.g., information) may include thresholds (e.g., one or more) for the correlation between channels of different TRPs. For example, a first correlation threshold may be used to determine the anchor based (e.g., type of) joint differential CSI compression, and a second (e.g., lower than the first) correlation threshold may be used to determine the non-anchor based (e.g., type of) joint differential CSI compression.

[0331] In case of non-anchor-based compression, the WTRU may be configured to (e.g., separately) determine (e.g., compute) the differential CSI for each TRP (e.g., of a set of TRPs).

[0332] In a third example, the configuration (e.g., information) may indicate a subset of TRPs for computing side information. The WTRU may receive configuration information indicating a subset of TRPs for computing and reporting side information for mismatch detection. In case of anchor-based compression, the WTRU may be (e.g., implicitly) configured to report side information for the channel of the anchor TRP. In case of non-anchor-based compression, the WTRU may be configured to report side information that may correspond to the subset of TRP channels.

[0333] In various embodiments, the WTRU may be configured to use any of anchor-based and non-anchor based differential CSI compression for multi-TRP by (e.g., receiving an) indication from the NW, any of semi-statically via RRC, and (e.g., more dynamically) via MAC CE and/or DCI signaling. The parameters for anchor-based or non-anchor-based differential CSI compression for multi-TRP method at the WTRU may be configured (e.g., indicated via configuration information) any of semi-statically via RRC, and (e.g., more dynamically) via MAC CE and/or DCI signaling.

WTRU Procedures on Joint Differential CSI Compression for Multi-TRP

[0334] WTRU methods for joint differential CSI compression for multi-TRP are described herein.

Non-Anchor-Based Joint Compression WTRU Procedures

[0335] A WTRU, configured with non-anchor-based CSI compression for a set of TRPs (multi- TRP), may receive one or more CSI-RS from (e.g., each TRP from) the set of TRPs and an indication to feedback CSI report to one or more of the TRPs.

[0336] In an example, the WTRU may determine (e.g., compute) a low-resolution PMI, which may be referred to herein as W_PMy and an ideal precoding matrix, which may be referred to herein as Wi_DE j for the set of (e.g., all) TRPs. The WTRU may determine (e.g., compute) the differential 4? CSI for each TRP (which may be referred to herein as TRPi), e.g., based on a difference between the ideal precoding matrix and the low-resolution PMI for that TRPi, such that W_{Diff t} = W_{IDE t} — W_{PMI £}. All computed differential CSIs, e.g., W_{Diff l},..., W_{Diff m}, where m may be referred to herein as the number of TRPs, may be compressed jointly using a single encoder. The output of the encoder may be represented as /(W_{Diff l}, W_{Diff m}). The WTRU may determine (e.g., compute side information

for (e.g., all) TRPs that may be used for mismatch detection. The WTRU may report (e.g., transmit feedback information indicating) any of

[0337] In another example, the WTRU may be configured to determine (e.g., compute) side information for a subset of TRP channels. For example, the WTRU may be configured to report (e.g., only) one side information (e.g., for one TRP). In this case, if mismatch is detected at the NW, then for (e.g., all) TRPs reported PMI may be reconstructed as the CSI. In another example, the WTRU may determine (e.g., compute, e.g., and report) side information for a subset of TRPs. In this case, if mismatch is detected via side information, then (e.g., only) the corresponding TRP channel (e.g., for which a mismatch may be detected) may fall back to low resolution PMI.

[0338] FIG. 8 is a diagram illustrating an example of non-anchor-based joint CSI compression. A first low-resolution precoding matrix 811 and a first ideal precoding matrix 812 may be determined for a first TRP. A first differential CSI 813 may be determined for the first TRP based on the first low-resolution precoding matrix 811 and the first ideal precoding matrix 812.

[0339] A second low-resolution precoding matrix 821 and a second ideal precoding matrix 822 may be determined for a second TRP. A second differential CSI 823 may be determined for the second TRP based on the second low-resolution precoding matrix 821 and the second ideal precoding matrix 822. The first differential CSI 813 and the second differential CSI 823 may be jointly compressed with a single encoder 830, resulting in a jointly compressed differential CSI 825.

[0340] A first side information 814 may be determined for the first TRP based on the first low- resolution precoding matrix 811 and the first differential CSI 813. A second side information 824 may be determined for the second TRP based on the second low-resolution precoding matrix 811 and the second differential CSI 823.

[0341] Any of the first low-resolution precoding matrix 811, the first side information 814, the jointly compressed differential CSI 825, the second low-resolution precoding matrix 821, and the second side information 824 may be reported by the WTRU to the NW.

Anchor-Based Joint Compression WTRU Procedures [0342] A WTRU, configured with anchor-based CSI compression for multi-TRP, may receive one or more CSI-RS from (e.g., each of) the TRPs in the set of multiple TRPs and an indication to feedback CSI report.

[0343] In one example, the WTRU may determine (e.g., compute) a low-resolution precoding matrix (which may be referred to herein as W_{PMI ;1}) for the (e.g., indicated) anchor TRP and an ideal precoding matrix (which may be referred to herein as Wj_DE ) for (e.g., all) TRPs of the set of multiple TRPs. The WTRU may determine (e.g., compute) the differential CSI for each TRP (which may be referred to herein as TRPi) relative to the low-resolution precoding matrix of the anchor TRP e.g., based on a difference between the ideal precoding matrix for that TRPi and the low-resolution PMI for the anchor TRP, such that W_{Diff £} = Wj_DE j — W_{PMI 1} . All computed differential CSIs, e.g., W_{Diff l},..., W_{Diff m}, where m may be referred to herein as the number of TRPs, may be compressed jointly using a single encoder. The output of the encoder may be represented as f (W_{Diff 1(} ... , W_{Diff m}). The WTRU may determine (e.g., compute) side information for a subset of TRPs that may be used for mismatch detection. The WTRU may report (e.g., transmit feedback information indicating) any

and a subset of

[^sDiff,l< ■■■ ’ ^sDiff, ml •

[0344] In another example, the WTRU may determine the anchor TRP. For example, the WTRU may determine an anchor TRP based on the channel corresponding to the anchor TRP satisfying a condition (e.g., having the highest average correlation with the channels of other TRPs). In this case, the WTRU may (e.g., additionally) report the index of the anchor TRP.

[0345] FIG. 9 is a diagram illustrating an example of anchor-based joint CSI compression. The first TRP may be the anchor TRP. A low-resolution precoding matrix 910 and a first ideal precoding matrix 911 may be determined for the anchor TRP. A first differential CSI 914 may be determined for the anchor TRP based on the low-resolution precoding matrix 910 and the first ideal precoding matrix 911.

[0346] A second ideal precoding matrix 912 and a third ideal precoding matrix 913 may be determined for respectively a second TRP and a third TRP. A second differential CSI 915 may be determined for the second TRP based on the low-resolution precoding matrix 910 and the second ideal precoding matrix 912. A third differential CSI 916 may be determined for the third TRP based on the low-resolution precoding matrix 910 and the third ideal precoding matrix 913. The first differential CSI 914, the second differential CSI 915, the third differential CSI 916 and any other differential CSI associated with any other TRP may be jointly compressed with a single encoder 930, resulting in a jointly compressed differential CSI 918. [0347] Side information 917 may be determined for the anchor TRP based on the low-resolution precoding matrix 910 and the first differential CSI 914.

[0348] Any of the low-resolution precoding matrix 910, the side information 917 and the jointly compressed differential CSI 918 may be reported by the WTRU to the NW.

[0349] In an embodiment, the WTRU may be configured to determine the type of joint CSI compression. In an example, the WTRU may determine the type of joint CSI compression based on correlation. For example, if the correlation among the channels corresponding to different TRPs satisfies a first condition (e.g., is above the configured first correlation threshold, the WTRU may determine to use the anchor-based method. If the measured correlation fails to satisfy a second condition (e.g., is below the configured second correlation threshold), the WTRU may determine to use the non-anchor-based method. Otherwise, the WTRU may continue to use the current type of joint differential CSI compression.

[0350] In one example, the WTRU may determine (e.g., compute) correlation of channels after (e.g., every) channel measurement done by using the received CSI-RS.

[0351] In another example, the WTRU may determine (e.g., compute) the correlation of channels using a specific period e.g., configured by the NW.

[0352] In another example, the WTRU may determine the period of correlation computation as a function of WTRU specific factors, such as e.g., WTRU speed. For example, the WTRU may determine to compute the correlation more frequently (e.g., the period between consecutive correlation computations may be smaller) when the WTRU speed may be higher (e.g., increase). In another example, the WTRU may determine the period of correlation computation as a function of the coherence time of the channel to a (e.g., each) TRP (e.g., the correlation computation period may be smaller than or equal to the minimum of the coherence times of the channel to each TRP). [0353] In another example, the WTRU may (e.g., first) compute the changes (e.g., of a metric) in each channel, e.g., by computing the historical difference (e.g., of the metric) between different time instances of the channels. If the change (e.g., of the metric) in one or more of the channels satisfies a condition (e.g., is above a threshold), the WTRU may determine to compute the correlation of the channels.

WTRU Reporting on Joint Differential CSI Compression for Multi- TRP

[0354] WTRU reporting on joint differential CSI compression may be determined according to the configuration(s) on joint differential CSI compression.

[0355] If the WTRU is configured with a non-anchor-based method, or if the WTRU determines to use a non-anchor-based method, the WTRU may report (e.g., transmit feedback information indicating) any of (i) a low-resolution precoding matrix corresponding to the channels of one or more (e.g., all) TRPs, (ii) the jointly compressed difference of low resolution precoding matrix and ideal precoding matrix for one or more (e.g., all) TRPs, and (iii) a subset of side information for mismatch detection at the NW.

[0356] If the WTRU is configured with an anchor-based method, of if the WTRU determines to use an anchor-based method, the WTRU may report (e.g., transmit feedback information indicating) any of (i) a low-resolution precoding matrix corresponding to the anchor TRP, (ii) the jointly compressed difference of low-resolution precoding matrix and ideal precoding matrix for one or more (e.g., all) TRPs, (iii) a subset of side information for mismatch detection at the NW, and (iv) if the WTRU is configured to determine an anchor TRP, the index (e.g., an indication) of the anchor TRP.

[0357] If the WTRU is configured to determine the type of compression, e.g., anchor-based or non-anchor-based, the WTRU may report the type of joint compression to the NW.

[0358] The WTRU may send the feedback information over uplink channels as indicated by the NW, such as e.g., any of physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH).

Example of Joint Differential CSI Compression for Multi-TRP

[0359] In an embodiment, a WTRU may compute jointly compressed differential CSI for a plurality of TRPs based on the difference between ideal CSI and low-resolution codebook-based CSI of (e.g., all TRPs of) the plurality of TRPs, and may report any of jointly compressed differential CSI, one or more PMIs, one or more mismatch metrics and an index of anchor TRP.

[0360] In a first step, the WTRU may receive configuration information related to joint differential CSI compression for multi-TRP indicating any of (i) the identification of TRPs to be used for joint differential CSI compression, (ii) the type of joint differential CSI compression for multi-TRP, for example, any of anchor-based and non-anchor-based, (iii) in case of anchor-based method, any of the index of the anchor TRP, and an indication to determine the anchor TRP, and (iv) a subset of TRPs for computing side information.

[0361] In a second step, the WTRU may receive one or more CSI-RS and may compute the differential CSI.

[0362] In case of anchor-based joint differential CSI compression, the WTRU may determine the anchor TRP. The WTRU may compute a low-resolution Type I/II codebook-based precoding matrix for the anchor TRP. The WTRU may compute ideal precoding matrices for (e.g., all) configured TRPs, the WTRU may compute the difference of ideal precoding matrices with the low-resolution precoding matrix of the anchor TRP, e.g., differential CSIs. The WTRU may jointly compress (e.g., all) the differential CSIs with a single encoder. The WTRU may compute one or more side information according to configuration. [0363] In case of non-anchor-based joint differential CSI compression, the WTRU may compute low-resolution Type I/II codebook-based precoding matrix for (e.g., all) the TRPs. The WTRU may compute ideal precoding matrices for (e.g., all) the configured TRPs. For a (e.g., each) configured TRP, the WTRU may compute the difference of ideal precoding matrices with the low- resolution precoding matrices, e.g., differential CSIs. The WTRU may jointly compress (e.g., all) the differential CSIs with a single encoder. The WTRU may compute one or more side information according to configuration.

[0364] In a third step, the WTRU may send feedback information on joint differential CSI compression for multi-TRP.

[0365] In case the WTRU sends feedback information (e.g., indicating one or more CSI reports) for non-anchor based joint CSI compression, the feedback information may indicate any of (i) the low-resolution precoding matrix corresponding to the channels of (e.g., all) TRPs, (ii) the jointly compressed difference of low-resolution precoding matrix and ideal precoding matrix for (e.g., all) TRPs, and (iii) a subset of side information for mismatch detection at the NW.

[0366] In case the WTRU sends feedback information (e.g., indicating one or more CSI reports) for anchor based joint CSI compression, the feedback information may indicate any of (i) the low- resolution precoding matrix corresponding to the anchor TRP, (ii) the jointly compressed difference of low resolution precoding matrix and ideal precoding matrix for all TRPs, (iii) a subset of side information for mismatch detection at the NW, and (iv) if the WTRU is configured to determine an anchor TRP, the index (e.g., indication) of the anchor TRP used for joint CSI compression.

Life Cycle Management for Differential CSI Compression

[0367] Life cycle management (LCM) methods for differential CSI compression are described herein.

Model Monitoring at the WTRU

[0368] The WTRU may receive configuration information on the LCM procedures regarding the differential CSI compression methods. For model monitoring at the WTRU side, the WTRU may be configured with performance thresholds on any of fallback to legacy (e.g., operation), switch to full CSI compression and switching/retraining the model.

[0369] As an example, the WTRU may determine and request fallback to legacy based on comparing the variation of historical ideal CSI against a (e.g., configured) threshold. In case the average variation is above a threshold, the WTRU may fallback to legacy (e.g., operation) to improve robustness. [0370] As an example, the WTRU may determine and request fallback to legacy (e.g., operation) based on comparing the historical SGCS difference between codebook-based PM and ideal PM against a (e.g., configured) threshold. In case the average of historical SGCS difference is below a (e.g., configured) threshold, then the WTRU may fallback to legacy operation (e.g., considering differential PM may be small).

[0371] As an example, the WTRU may determine and request to switch to full CSI compression based on comparing the historical SGCS difference between codebook-based PM and ideal PM against a (e.g., configured) threshold. In case the average of historical SGCS difference is above a (e.g., configured) threshold, then the WTRU may determine to use full CSI compression considering that the differential PM may occupy a large payload.

[0372] As an example, the WTRU may determine and request to any of switch and retrain the AI/ML model based on comparing the historical BLER against a configured (e.g., threshold). In case the average BLER is above a threshold, then the WTRU may determine to any of switch and retrain the AI/ML model.

Model monitoring at the NW

[0373] The WTRU may receive an indication to any of (i) fallback to legacy operation, (ii) model update and/or retraining, and (iii) use full CSI compression etc. based on model monitoring at NW. [0374] In an example, the NW may compare the historical average of mismatch against a threshold.

[0375] In another example, the NW may compare the number of consecutive mismatches against a threshold.

[0376] In another example, the NW may compare the historical average BLER against a threshold.

Trigger/Switch/Update of the Differential CSI Compression

[0377] The WTRU may receive an indication to any of (i) fallback to legacy operation, (ii) model update and/or retraining, and (iii) use full CSI compression etc. based on model monitoring at NW. [0378] The WTRU may determine to any of (i) fallback to legacy operation, (ii) model update and/or retraining, and (iii) use full CSI compression etc. based on model monitoring at the WTRU, and may report to NW.

Example Method for Differential CSI Compression and Feedback on Mismatch Detection [0379] FIG. 10 is a diagram illustrating an example method 1000 for differential CSI compression and feedback on mismatch detection. The method 1000 may be implemented in a WTRU. As shown at 1010, the WTRU may receive one or more reference signals. As shown at 1020, the WTRU may determine a first precoding matrix and one or more second precoding matrices based on the one or more reference signals. As shown at 1030, the WTRU may determine one or more differential CSI based on the first precoding matrix and the one or more second precoding matrices. As shown at 1040, the WTRU may determine one or more compressed differential CSI based on the one or more differential CSI. As shown at 1050, the WTRU may determine side information based on the one or more differential CSI and the first precoding matrix. As shown at 1060, the WTRU may transmit feedback information indicating the one or more compressed differential CSI and the side information.

[0380] In various embodiments, the WTRU may receive configuration information indicating to use differential CSI compression.

[0381] In various embodiments, the configuration information may indicate any of (i) a payload size for codebook-based precoding matrix feedback, (ii) a payload size for differential CSI compression feedback, (iii) any of uplink resources and resource types associated with different parts of a CSI report, and (iv) one or more rules for the WTRU to determine a reporting configuration.

[0382] In various embodiments, the first precoding matrix may be a lower resolution precoding matrix, and the one or more second precoding matrices may be higher resolution precoding matrices.

[0383] In various embodiments, the first precoding matrix may correspond to a wideband channel.

[0384] In various embodiments, the one or more second precoding matrices may correspond to respectively one or more sub-bands.

[0385] In various embodiments, the WTRU may determine a first channel quality indicator associated with the first precoding matrix and one or more second channel quality indicators associated with the one or more second precoding matrices.

[0386] In various embodiments, the feedback information may indicate any of the first channel quality indicator and the one or more second channel quality indicators.

[0387] In various embodiments, the feedback information may indicate the first precoding matrix.

[0388] In various embodiments, a first part of the feedback information may be transmitted in response to a first differential CSI request, and the first part of the feedback information may indicate the first channel quality indicator, the one or more second channel quality indicators and the first precoding matrix.

[0389] In various embodiments, a second part of the feedback information may be transmitted in response to a second differential CSI request, and the second part of the feedback information may indicate the one or more compressed differential CSI. [0390] FIG. 11 is a diagram illustrating an example method 1100 for differential CSI compression. The method 1100 may be implemented in a WTRU. As shown at 1110, the WTRU may receive one or more reference signals. As shown at 1120, the WTRU may select a first codebook-based precoding matrix based on the one or more reference signals and the WTRU may determine a second precoding matrix based on the one or more reference signals. As shown at 1130, the WTRU may determine a differential precoding matrix based on the selected first codebook-based precoding matrix and the determined second precoding matrix. As shown at 1140, the WTRU may determine a compressed differential precoding matrix based on the differential precoding matrix. As shown at 1150, the WTRU may transmit feedback information indicating the compressed differential precoding matrix.

[0391] In various embodiments, the WTRU may determine side information based on the differential precoding matrix and the first codebook-based precoding matrix.

[0392] In various embodiments, the feedback information may indicate the side information.

[0393] In various embodiments, the side information may be representative of (e.g., indicate) any of a magnitude and a relative magnitude of an autoencoder input.

[0394] In various embodiments, the WTRU may receive configuration information indicating to use differential CSI compression.

[0395] In various embodiments, the configuration information may indicate any of (i) a payload size for codebook-based precoding matrix feedback, (ii) a payload size for differential CSI compression feedback, (iii) any of uplink resources and resource types associated with different parts of a CSI report, and (iv) one or more rules for the WTRU to determine a reporting configuration.

[0396] In various embodiments, the first codebook-based precoding matrix may be a lower resolution precoding matrix, and the second precoding matrix may be a higher resolution precoding matrix.

[0397] In various embodiments, the first codebook-based precoding matrix may correspond to a wideband channel.

[0398] In various embodiments, the second precoding matrix may correspond to a sub-band.

[0399] In various embodiments, the WTRU may determine a first channel quality indicator associated with the first codebook-based precoding matrix and a second channel quality indicator associated with the second precoding matrix.

[0400] In various embodiments, the feedback information may indicate any of the first channel quality indicator and the second channel quality indicator.

[0401] In various embodiments, the feedback information may indicate the first codebook-based precoding matrix. [0402] In various embodiments, a first part of the feedback information may be transmitted in response to a first differential CSI request, and the first part of the feedback information may indicate the first channel quality indicator, the second channel quality indicator and the first codebook-based precoding matrix.

[0403] In various embodiments, a second part of the feedback information may be transmitted in response to a second differential CSI request, and the second part of the feedback information may indicate the compressed differential precoding matrix.

Example Method for Determining and Reporting the Parameters for Differential CSI Compression

[0404] FIG. 12 is a diagram illustrating an example method 1200 for determining and reporting the parameters for differential CSI compression. The method 1200 may be implemented in a WTRU. As shown at 1210, the WTRU may receive one or more reference signals. As shown at 1220, the WTRU may determine a second precoding matrix based on the one or more reference signals. As shown at 1230, the WTRU may determine one or more parameters for codebook-based precoding matrix and differential CSI compression based on the second precoding matrix. As shown at 1240, the WTRU may determine a first precoding matrix based on the one or more reference signals and the determined one or more parameters. As shown at 1250, the WTRU may determine a compressed differential CSI based on the first precoding matrix, the second precoding matrix and the determined one or more parameters. As shown at 1260, the WTRU may transmit feedback information indicating the compressed differential CSI and the determined one or more parameters.

[0405] In various embodiments, the WTRU may receive configuration information indicating the WTRU to determine the one or more parameters for codebook-based precoding matrix and differential CSI compression.

[0406] In various embodiments, the configuration information may indicate any of (i) a payload size for transmitting the feedback information and (ii) to use differential CSI compression.

[0407] In various embodiments, the first precoding matrix may be a codebook-based precoding matrix, and the second precoding matrix may be a non-codebook-based precoding matrix.

[0408] In various embodiments, the first precoding matrix may correspond to a wideband channel.

[0409] In various embodiments, the second precoding matrix may correspond to a sub-band.

[0410] In various embodiments, the WTRU may determine a differential CSI based on the first precoding matrix and the second precoding matrix.

[0411] In various embodiments, the compressed differential CSI may be determined by compressing the differential CSI. [0412] In various embodiments, the one or more parameters may include any of payload sizes, a type of side information and a codebook type for precoding matrices.

[0413] In various embodiments, the one or more parameters may be determined further according to any of a set of allowed values, a use of a decoder, a performance metric calculation and a feedback report type.

[0414] In various embodiments, the WTRU may determine side information based on the differential CSI and the first precoding matrix.

[0415] In various embodiments, the feedback information may indicate the side information.

[0416] In various embodiments, the feedback information may indicate the first precoding matrix.

Example Method for Windowed Differential CSI Compression

[0417] FIG. 13 is a diagram illustrating an example method 1300 for windowed differential CSI compression. The method 1000 may be implemented in a WTRU. As shown at 1310, the WTRU may receive a first reference signal at a first time instance at a beginning of a time window. As shown at 1320, the WTRU may determine a first precoding matrix based on the first reference signal. As shown at 1330, the WTRU may receive a second reference signal at a second time instance within the time window. As shown at 1340, the WTRU may determine a second precoding matrix based on the second reference signal. As shown at 1350, the WTRU may determine a second compressed differential CSI based on the first precoding matrix and the second precoding matrix. As shown at 1360, the WTRU may transmit second feedback information at a second reporting occasion associated with the second time instance. In various embodiments, the second feedback information may indicate the second compressed differential CSI.

[0418] In various embodiments, the WTRU may transmit first feedback information at a first reporting occasion associated with the first time instance. In various embodiments, the first feedback information may indicate the first precoding matrix.

[0419] In various embodiments, the first reporting occasion may occur before the second time instance and before the second reporting occasion. In various embodiments, the first reporting occasion may occur after the first time instance, and the second reporting occasion may occur after the first time instance.

[0420] In various embodiments, the WTRU may determine a third precoding matrix based on the first reference signal.

[0421] In various embodiments, the WTRU may determine a first compressed differential CSI based on the first precoding matrix and the third precoding matrix.

[0422] In various embodiments, the first feedback information may indicate the first compressed differential CSI. [0423] In various embodiments, the WTRU may receive configuration information indicating the WTRU to determine a size of the time window.

[0424] In various embodiments, the size of the time window may be determined based on a channel coherence time.

[0425] In various embodiments, the WTRU may receive configuration information indicating a size of the time window.

[0426] In various embodiments, wherein the configuration information may indicate any of (i) a payload size for codebook-based precoding matrix feedback, (ii) a payload size for differential CSI compression feedback, and (iii) to use differential CSI compression.

[0427] In various embodiments, the first precoding matrix may be a lower resolution precoding matrix, and any of the second precoding matrix and the third precoding matrix may be a higher resolution precoding matrix.

[0428] In various embodiments, the first precoding matrix may correspond to a wideband channel.

[0429] In various embodiments, any of the second precoding matrix and the third precoding matrix may correspond to a sub-band.

[0430] In various embodiments, the WTRU may determine that an error occurred while (e.g., when) transmitting the first feedback information. In a first example, the WTRU may receive information indicating a negative acknowledge associated with the transmission of the first feedback information. In a second example, the WTRU may monitor for a positive acknowledge after the transmission of the first feedback information. The WTRU may determine that an error occurred when transmitting the first feedback information in a case where no positive acknowledge associated with the transmission of the first feedback information has been received within an amount of time after the transmission of the first feedback information.

[0431] In various embodiments, the WTRU may transmit third feedback information indicating the first precoding matrix based on the determining that an error occurred while transmitting the first feedback information. In various embodiment, the third feedback information may be transmitted in the time window.

Example Method for Joint Differential CSI Compression for Multi- TRP

[0432] FIG. 14 is a diagram illustrating an example method 1400 for joint differential CSI compression for multi-TRP. The method 1400 may be implemented in a WTRU. As shown at 1410, the WTRU may receive a plurality of reference signals from a plurality of network elements. As shown at 1420, the WTRU may determine at least one first precoding matrix for at least one network element of the plurality of network elements. As shown at 1430, the WTRU may determine a plurality of second precoding matrices for the plurality of network elements based on the plurality of reference signals. As shown at 1440, the WTRU may determine a plurality of differential CSI elements based on the at least one first precoding matrix and the plurality of second precoding matrices. As shown at 1450, the WTRU may determine a jointly compressed differential CSI based on the plurality of differential CSI elements. As shown at 1460, the WTRU may transmit feedback information indicating the jointly compressed differential CSI.

[0433] In various embodiments, the jointly compressed differential CSI may be determined with a single encoder.

[0434] In various embodiments, the WTRU may receive configuration information indicating a subset of network elements of the plurality of network elements for determining side information. [0435] In various embodiments, the WTRU may determine the side information based on the configuration information.

[0436] In various embodiments, the feedback information may indicate the side information.

[0437] In various embodiments, the configuration information may indicate any of an anchorbased type of joint differential CSI compression and a non-anchor-based type of joint differential CSI compression.

[0438] In various embodiments, if the configuration information indicates an anchor-based joint type of differential CSI compression, the configuration information may further indicate (i) an index of an anchor network element or (ii) to determine the anchor network element.

[0439] In various embodiments, the at least one first precoding matrix may be (e.g., comprise) at least one lower resolution precoding matrix, and the plurality of second precoding matrices may be (e.g., comprise) higher resolution precoding matrices.

[0440] In various embodiments, the at least one first precoding matrix may correspond to at least one wideband channel.

[0441] In various embodiments, the plurality of second precoding matrices may correspond to respectively a plurality of sub-bands.

[0442] In various embodiments, a differential CSI element of the plurality of differential CSI elements may be based on a difference between (i) a first precoding matrix of the at least one first precoding matrix associated with a first network element of the plurality of network elements and (ii) a second precoding matrix of the plurality of second precoding matrices associated with any of the first network element and a second network element of the plurality of network elements.

[0443] In various embodiments, the WTRU may determine an anchor network element, and determining the at least one first precoding matrix may comprise determining a first precoding matrix for the anchor network element.

[0444] In various embodiments, a differential CSI element of the plurality of differential CSI elements may be based on a difference between the first precoding matrix for the anchor network element and a second precoding matrix of the plurality of second precoding matrices associated with the anchor network element or a network element of the plurality of network elements different from the anchor network element.

[0445] In various embodiments, the feedback information may indicate the first precoding matrix for the anchor network element.

[0446] In various embodiments, the feedback information may indicate the anchor network element used for determining the jointly compressed differential CSI.

[0447] In various embodiments, determining the at least one first precoding matrix may comprise determining a plurality of first precoding matrices for the plurality of network elements.

[0448] In various embodiments, the plurality of first precoding matrices may comprise a first precoding matrix for each network element of the plurality of network elements.

[0449] In various embodiments, the plurality of differential CSI elements may comprise a differential CSI element for each network element of the plurality of network elements based on a difference between the first precoding matrix for the network element and a second precoding matrix of the plurality of second precoding matrices for the network element.

[0450] In various embodiments, the feedback information may indicate the plurality of first precoding matrices for the plurality of network elements.

[0451] While not explicitly described, embodiments described herein may be employed in any combination or sub-combination. For example, the present principles are not limited to the described variants, and any arrangement of variants and embodiments can be used.

[0452] Besides, any characteristic, variant or embodiment described for a method is compatible with an apparatus device comprising means for processing the disclosed method, with a device comprising circuitry, including any of a transmitter, a receiver, a processor, a processor and a memory configured to process the disclosed method, with a computer program product comprising program code instructions and with a non-transitory computer-readable storage medium storing program instructions.

[0453] Although features and elements are provided above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations may be made without departing from its spirit and scope, as will be apparent to those skilled in the art. No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly provided as such. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods or systems.

[0454] The foregoing embodiments are discussed, for simplicity, with regard to the terminology and structure of infrared capable devices, i.e., infrared emitters and receivers. However, the embodiments discussed are not limited to these systems but may be applied to other systems that use other forms of electromagnetic waves or non-electromagnetic waves such as acoustic waves. [0455] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used herein, the term "video" or the term "imagery" may mean any of a snapshot, single image and/or multiple images displayed over a time basis. As another example, when referred to herein, the terms "user equipment" and its abbreviation "UE", the term "remote" and/or the terms "head mounted display" or its abbreviation "HMD" may mean or include (i) a wireless transmit and/or receive unit (WTRU); (ii) any of a number of embodiments of a WTRU; (iii) a wireless-capable and/or wired-capable (e.g., tetherable) device configured with, inter alia, some or all structures and functionality of a WTRU; (iii) a wireless-capable and/or wired-capable device configured with less than all structures and functionality of a WTRU; or (iv) the like. Details of an example WTRU, which may be representative of any WTRU recited herein, are provided herein with respect to FIGs. 1 A-1D. As another example, various disclosed embodiments herein supra and infra are described as utilizing a head mounted display. Those skilled in the art will recognize that a device other than the head mounted display may be utilized and some or all of the disclosure and various disclosed embodiments can be modified accordingly without undue experimentation. Examples of such other device may include a drone or other device configured to stream information for providing the adapted reality experience.

[0456] In addition, the methods provided herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

[0457] Variations of the method, apparatus and system provided above are possible without departing from the scope of the invention. In view of the wide variety of embodiments that can be applied, it should be understood that the illustrated embodiments are examples only, and should not be taken as limiting the scope of the following claims. For instance, the embodiments provided herein include handheld devices, which may include or be utilized with any appropriate voltage source, such as a battery and the like, providing any appropriate voltage.

[0458] Moreover, in the embodiments provided above, processing platforms, computing systems, controllers, and other devices that include processors are noted. These devices may include at least one Central Processing Unit ("CPU") and memory. In accordance with the practices of persons skilled in the art of computer programming, reference to acts and symbolic representations of operations or instructions may be performed by the various CPUs and memories. Such acts and operations or instructions may be referred to as being "executed," "computer executed" or "CPU executed."

[0459] One of ordinary skill in the art will appreciate that the acts and symbolically represented operations or instructions include the manipulation of electrical signals by the CPU. An electrical system represents data bits that can cause a resulting transformation or reduction of the electrical signals and the maintenance of data bits at memory locations in a memory system to thereby reconfigure or otherwise alter the CPU's operation, as well as other processing of signals. The memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to or representative of the data bits. It should be understood that the embodiments are not limited to the above-mentioned platforms or CPUs and that other platforms and CPUs may support the provided methods.

[0460] The data bits may also be maintained on a computer readable medium including magnetic disks, optical disks, and any other volatile (e.g., Random Access Memory (RAM)) or non-volatile (e.g., Read-Only Memory (ROM)) mass storage system readable by the CPU. The computer readable medium may include cooperating or interconnected computer readable medium, which exist exclusively on the processing system or are distributed among multiple interconnected processing systems that may be local or remote to the processing system. It should be understood that the embodiments are not limited to the above-mentioned memories and that other platforms and memories may support the provided methods.

[0461] In an illustrative embodiment, any of the operations, processes, etc. described herein may be implemented as computer-readable instructions stored on a computer-readable medium. The computer-readable instructions may be executed by a processor of a mobile unit, a network element, and/or any other computing device.

[0462] There is little distinction left between hardware and software implementations of aspects of systems. The use of hardware or software is generally (but not always, in that in certain contexts the choice between hardware and software may become significant) a design choice representing cost versus efficiency tradeoffs. There may be various vehicles by which processes and/or systems and/or other technologies described herein may be effected (e.g., hardware, software, and/or firmware), and the preferred vehicle may vary with the context in which the processes and/or systems and/or other technologies are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a mainly hardware and/or firmware vehicle. If flexibility is paramount, the implementer may opt for a mainly software implementation. Alternatively, the implementer may opt for some combination of hardware, software, and/or firmware.

[0463] The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Insofar as such block diagrams, flowcharts, and/or examples include one or more functions and/or operations, it will be understood by those within the art that each function and/or operation within such block diagrams, flowcharts, or examples may be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In an embodiment, several portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), and/or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, may be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure. In addition, those skilled in the art will appreciate that the mechanisms of the subject matter described herein may be distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies regardless of the particular type of signal bearing medium used to actually carry out the distribution. Examples of a signal bearing medium include, but are not limited to, the following: a recordable type medium such as a floppy disk, a hard disk drive, a CD, a DVD, a digital tape, a computer memory, etc., and a transmission type medium such as a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link, etc.).

[0464] Those skilled in the art will recognize that it is common within the art to describe devices and/or processes in the fashion set forth herein, and thereafter use engineering practices to integrate such described devices and/or processes into data processing systems. That is, at least a portion of the devices and/or processes described herein may be integrated into a data processing system via a reasonable amount of experimentation. Those having skill in the art will recognize that a typical data processing system may generally include one or more of a system unit housing, a video display device, a memory such as volatile and non-volatile memory, processors such as microprocessors and digital signal processors, computational entities such as operating systems, drivers, graphical user interfaces, and applications programs, one or more interaction devices, such as a touch pad or screen, and/or control systems including feedback loops and control motors (e.g., feedback for sensing position and/or velocity, control motors for moving and/or adjusting components and/or quantities). A typical data processing system may be implemented utilizing any suitable commercially available components, such as those typically found in data computing/communication and/or network computing/communication systems.

[0465] The herein described subject matter sometimes illustrates different components included within, or connected with, different other components. It is to be understood that such depicted architectures are merely examples, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality may be achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated may also be viewed as being "operably connected", or "operably coupled", to each other to achieve the desired functionality, and any two components capable of being so associated may also be viewed as being "operably couplable" to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

[0466] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. [0467] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, where only one item is intended, the term "single" or similar language may be used. As an aid to understanding, the following appended claims and/or the descriptions herein may include usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim including such introduced claim recitation to embodiments including only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should be interpreted to mean "at least one" or "one or more"). The same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B." Further, the terms "any of' followed by a listing of a plurality of items and/or a plurality of categories of items, as used herein, are intended to include "any of," "any combination of," "any multiple of," and/or "any combination of multiples of the items and/or the categories of items, individually or in conjunction with other items and/or other categories of items. Moreover, as used herein, the term "set" is intended to include any number of items, including zero. Additionally, as used herein, the term "number" is intended to include any number, including zero. And the term "multiple", as used herein, is intended to be synonymous with "a plurality".

[0468] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0469] As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein may be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as "up to," "at least," "greater than," "less than," and the like includes the number recited and refers to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth.

[0470] Moreover, the claims should not be read as limited to the provided order or elements unless stated to that effect. In addition, use of the terms "means for" in any claim is intended to invoke 35 U.S.C. §112, 6 or means-plus-function claim format, and any claim without the terms "means for" is not so intended.

Claims

CLAIMS What is claimed is:

1. A method implemented in a wireless transmit/receive unit (WTRU), the method comprising: receiving one or more reference signals; selecting a first codebook-based precoding matrix based on the one or more reference signals and determining a second precoding matrix based on the one or more reference signals; determining a differential precoding matrix based on the selected first codebook-based precoding matrix and the determined second precoding matrix; determining a compressed differential precoding matrix based on the differential precoding matrix; and transmitting feedback information indicating the compressed differential precoding matrix.

2. The method of claim 1, comprising determining side information based on the differential precoding matrix and the first codebook-based precoding matrix.

3. The method of claim 2, wherein the side information is representative of any of a magnitude and a relative magnitude of an autoencoder input.

4. The method of any of claims 2 to 3, wherein the feedback information indicates the side information.

5. The method of any of claims 1 to 4, comprising receiving configuration information indicating to use differential channel state information (CSI) compression.

6. The method of claim 5, wherein the configuration information indicates any of (i) a payload size for codebook-based precoding matrix feedback, (ii) a payload size for differential CSI compression feedback, (iii) any of uplink resources and resource types associated with different parts of a CSI report, and (iv) one or more rules for the WTRU to determine a reporting configuration.

7. The method of any of claims 1 to 6, wherein the first codebook-based precoding matrix is a lower resolution precoding matrix, and the second precoding matrix is a higher resolution precoding matrix.

8. The method of any of claims 1 to 7, wherein the first codebook-based precoding matrix corresponds to a wideband channel.

9. The method of any of claims 1 to 8, wherein the second precoding matrix corresponds to a subband.

10. The method of any of claims 1 to 9, comprising determining a first channel quality indicator associated with the first codebook-based precoding matrix and a second channel quality indicator associated with the second precoding matrix.

11. The method of claim 10, wherein the feedback information indicates any of the first channel quality indicator and the second channel quality indicator.

12. The method of claim 10, wherein the feedback information indicates the first codebook-based precoding matrix.

13. The method of claim 10, wherein a first part of the feedback information is transmitted in response to a first differential CSI request, and wherein the first part of the feedback information indicates the first channel quality indicator, the second channel quality indicator and the first codebook-based precoding matrix.

14. The method of claim 13, wherein a second part of the feedback information is transmitted in response to a second differential CSI request, and wherein the second part of the feedback information indicates the compressed differential precoding matrix.

15. A wireless transmit/receive unit (WTRU) comprising circuitry, including any of a transmitter, a receiver, a processor, and a memory, configured to: receive one or more reference signals; select a first codebook-based precoding matrix based on the one or more reference signals and determine a second precoding matrix based on the one or more reference signals; determine a differential precoding matrix based on the first codebook-based precoding matrix and the second precoding matrix; determining a compressed differential precoding matrix based on the differential precoding matrix; and transmitting feedback information indicating the compressed differential precoding matrix.

16. The WTRU of claim 15, wherein the circuitry is configured to determine side information based on the differential precoding matrix and the first codebook-based precoding matrix.

17. The WTRU of claim 16, wherein the feedback information indicates the side information.

18. The WTRU of any of claims 15 to 17, wherein the circuitry is configured to receive configuration information indicating to use differential channel state information (CSI) compression.

19. The WTRU of claim 18, wherein the configuration information indicates any of (i) a payload size for codebook-based precoding matrix feedback, (ii) a payload size for differential CSI compression feedback, (iii) any of uplink resources and resource types associated with different parts of a CSI report, and (iv) one or more rules for the WTRU to determine a reporting configuration.

20. The WTRU of any of claims 15 to 19, wherein the first codebook-based precoding matrix is a lower resolution precoding matrix, and the second precoding matrix is a higher resolution precoding matrix.