METHODS FOR COMPRESSING LINEARLY CODED MULTITRP-ENCLOSED CSI

Abstract

The invention relates to one or more methods, devices, and / or systems capable of providing techniques for compressing linearly encoded channel state (CS) information for multiple transmit / receive (mTRP) multiple points. This is capable of providing improvements to wireless communication systems, for example, by improving resilience to transmission errors and mismatches, general or specific compression of channel matrices from different TRPs, and / or reverting to legacy CSI reporting in mTRP CSI compression.

Description

METHODS FOR MULTI-TRP LINEAR CODED CSI COMPRESSIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Numbers 63 / 592,483, 63 / 592,489, and 63 / 592,499, all of which were filed October 23, 2023, and the contents of which are incorporated herein by reference.BACKGROUND

[0002] In any given wireless communication system it may be beneficial for all entities within the system to understand the signals that are being sent within the system. One approach that has been used in legacy system is to transmit channel state information reports regarding the properties of one or more specific types of signals.SUMMARY

[0003] One or more methods, devices, and / or systems may provide techniques for linear coded channel state information (CS) compression for multi-transmission / receive point(s) (mTRP). This may provide improvements to wireless communication systems, for example, by improving resilience against transmission errors and mismatch, joint or separate compression of channel matrices from different TRPs, and / or fallback to legacy CSI reporting operation in mTRP CSI compression.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0005] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0006] FIG. 1 B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0007] FIG. 1 C 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. 1 A according to an embodiment;

[0008] FIG. 1 D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment;

[0009] FIG. 2 illustrates an example of codebook-based precoding with feedback information;

[0010] FIG. 3 illustrates an example of CSI reporting for m-TRP;

[0011] FIG. 4 illustrates an example of AI / ML framework for CSI feedback;

[0012] FIG. 5 illustrates an example of linear coded CSI compression mechanism for mTRP with separate encoder / decoder (option-a);

[0013] FIG. 6 illustrates an example of linear coded joint CSI compression mechanism for mTRP with joint (e.g. , single) encoder / decoder (option-b);

[0014] FIG. 7 illustrates an example of different compression types using autoencoder; and

[0015] FIG. 8 illustrates an example process according to one or more embodiments disclosed herein.DETAILED DESCRIPTION

[0016] As discussed herein, one or more of the following terms may be abbreviated: ACK (Acknowledgement), AE (Autoencoder), BLER (Block Error Rate), BWP (Bandwidth Part), CAP (Channel Access Priority), CAPC (Channel access priority class), CCA (Clear Channel Assessment), CCE (Control Channel Element), CE (Control Element), CG (Configured grant or cell group), CP (Cyclic Prefix), CP-OFDM (Conventional OFDM relying on cyclic prefix), CQI (Channel Quality Indicator), CRC (Cyclic Redundancy Check), CSI (Channel State Information), CW (Contention Window), CWS (Contention Window Size), CO (Channel Occupancy), DAI (Downlink Assignment Index), DCI (Downlink Control Information), DFI (Downlink feedback information), DG (Dynamic grant), DL (Downlink), DM-RS (Demodulation Reference Signal), DRB (Data Radio Bearer), eLAA (enhanced Licensed Assisted Access), FeLAA (Further enhanced Licensed Assisted Access), HARQ (Hybrid Automatic Repeat Request), LAA (License Assisted Access), LBT (Listen-Before-Talk), LTE (Long Term Evolution from 3GPP LTE R8 and up), NACK (Negative ACK), MCS (Modulation and Coding Scheme), MIMO (Multiple Input Multiple Output), NR (New Radio), OFDM (Orthogonal Frequency-Division Multiplexing), PHY (Physical Layer), PID (Process ID), PO (Paging Occasion), PRACH (Physical Random Access Channel), PSS (Primary Synchronization Signal), RA (Random Access or procedure), RACH (Random Access Channel), RAR (Random Access Response), RCU (Radio access network Central Unit), RF (Radio Front end), RLF (Radio Link Failure), RLM (Radio Link Monitoring), RNTI (Radio Network Identifier), RO (RACH occasion), RRC (Radio ResourceControl), RRM (Radio Resource Management), RS (Reference Signal), RSRP (Reference Signal Received Power), RSSI (Received Signal Strength Indicator), SDU (Service Data Unit), SGCS (Squared Generalized Cosine Similarity), SRS (Sounding Reference Signal), SS (Synchronization Signal), SSS (Secondary Synchronization Signal), SWG (Switching Gap in a self-contained subframe), SPS (Semi-persistent scheduling), SUL (Supplemental Uplink), TB (Transport Block), TBS (Transport Block Size), TRP (Transmission / Reception Point), TSC (Time-sensitive communications), TSN (Time-sensitive networking), UL (Uplink), URLLC (Ultra-Reliable and Low Latency Communications), WBWP (Wide Bandwidth Part), WLAN (Wireless Local Area Networks and related technologies in the IEEE 802. xx domain).

[0017] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0018] 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, a core network (CN) 106, 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 (ST A), may be configured to transmit and / or receive wireless signals and may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (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 consumerelectronics 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.

[0019] The communications systems 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the CN 106, the Internet 110, and / or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 1 14b 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.

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

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

[0022] More specifically, as noted above, the 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 and theWTRUs 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 1 16 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as High-Speed Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High- Speed Downlink (DL) Packet Access (HSDPA) and / or High-Speed Uplink (UL) Packet Access (HSUPA).

[0023] 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).

[0024] 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 NR.

[0025] 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).

[0026] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1 X, 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.

[0027] 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 one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In an embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.)to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 1 10. Thus, the base station 114b may not be required to access the Internet 110 via the CN 106.

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

[0029] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 1 10, and / or the other networks 112. The PSTN 108 may include circuit- switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and / or the internet protocol (IP) in the TCP / IP internet protocol suite. The networks 112 may include wired and / or wireless communications networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0030] 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.

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

[0032] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), 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 1 18 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0033] The transmit / receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g ., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In an embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0034] Although the transmit / receive element 122 is depicted in FIG. 1 B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0035] The transceiver 120 may be configured to modulate 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.

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

[0037] 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.

[0038] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information 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.

[0039] The processor 1 18 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e- compass, a satellite transceiver, a digital camera (for photographs and / or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a 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 peripherals 138 may include one or more sensors. The sensors may be one or more of a gyroscope, an accelerometer, a hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor; a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor and the like.

[0040] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and DL (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 selfinterference 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 halfduplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g., for transmission) or the DL (e.g., for reception)).

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

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

[0043] Each of the eNode-Bs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, and the like. As shown in FIG. 1 C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0044] The CN 106 shown in FIG. 1 C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

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

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

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

[0048] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional landline 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.

[0049] Although the WTRU is described in FIGS. 1A-1 D 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.

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

[0051] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic in to 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 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of theSTAs) 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.

[0052] When using the 802.11ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width. 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 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.

[0053] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0054] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. The 40 MHz, and / or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 contiguous 20 MHz channels, or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0055] Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11ah relative to those used in 802.11n, and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support Meter Type Control / Machine-Type Communications (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).

[0056] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and / or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 1 MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode) transmitting to the AP, all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

[0057] In the United States, the available frequency bands, which may be used by 802.11 ah, 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 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0058] FIG. 1 D 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 NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0059] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and / or receive wireless signals from, the WTRU 102a. In an embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and / or gNB 180c).

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

[0061] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In 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.

[0062] 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, DC, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0063] The CN 106 shown in FIG. 1 D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0064] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 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 non- access stratum (NAS) signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, and the like. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE- A, LTE-A Pro, and / or non-3GPP access technologies such as WiFi.

[0065] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to a U PF 184a, 184b in the CN 106 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 DL data notifications, and the like. A PDU session type may be IP-based, non-IP based, Ethernet-based, and the like.

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

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

[0068] In view of FIGs. 1A-1 D, and the corresponding description of FIGs. 1A-1 D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a- b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and / or any other device(s) described herein, may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more, or all, of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0069] 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 performing testing using over-the-air wireless communications.

[0070] 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.

[0071] FIG. 2 illustrates an example of codebook-based precoding with feedback information. As described herein, feedback may be interchangeable with CSI repot, however, it may be understood that feedback may be any other kind of feedback and CSI is used for illustrative purposes. Generally, 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 the figure. A codebook may include a set of precoding vectors / matrices for each rank and the number of antenna ports, and each precoding vectors / matrices may have its own index so that a receiver may inform preferred precoding vector / matrix index to a transmitter. The codebook-based precoding may have performance degradation due to its finite number of precoding vector / matrix as compared with non-codebook-based precoding. However, a major advantage of a codebook-based precoding may be lower control signaling / feedback overhead.Said another way, it may be beneficial if there was a way to increase the performance while still maintaining lower overhead if a more efficient feedback system was in place.

[0072] From the illustrations of FIG. 2 an example of codebook-based precoding with feedback information may be better understood. For this example, there may be a transmitter 211 , a MIMO channel 212, and a receiver 213. At 202, there may be one or more inputs (XMI) 202 into the transmitter 211. At 204, there may be one or more outputs (Zi,..., ZNI) from the transmitter 211 for transmission (e.g., via ZNI multiple antennas, mapped to specific antenna ports based on the precoding). For example, the subscript Ml represents the number of data streams prior to undergoing the transformation based on the precoding matrix (W=Pi), which would then transform (Xi,..., ZMI) 202 to (Zi ,..., ZNI) 204 using the precoder Pi.. The feedback codeword index I of precoder Pi is feedback from receiver to 213 to transmitter 211 over feedback channel 214. Having been transformed, this output (Zi ,..., ZNI) 204 can now be sent via multiple antennas over the MIMO channel 212. At 206, there may be inputs (r1 ,..., rNr) (e.g., transmissions over the MIMO channel) that may be received at receiver 213 and transformed back to the original inputs, for example using a maximum likelihood (ML) or minimum mean-squared error (MMSE) based receiver processing.

[0073] FIG. 3 illustrates an example of CSI reporting for multi-transmission / receive point(s) (m- TRP). In new radio (NR) there is a need for enhancements to CSI reporting framework in order to support a more efficient reporting setting for scenarios with multiple TRPs in Non-Coherent Joint Transmission (NCJT). For example, there may be an approach to improve CSI acquisition for FDD Coherent Joint Transmission (CJT) through enhancements to the Type II CSI reporting framework.

[0074] From the illustration of FIG. 3 an example of CSI reporting for mTRP may be better understood. For this example, there may be a first TRP 301 , a second TRP 302, and a third TRP 303, and a WTRU 304 that may communicate with one or more of the TRPs (mTRP). As shown in this example, the WTRU 304 may receive a CSI reference signal from one or more of the mTRP and send a CSI report back, to the third TRP 303 in this case.

[0075] FIG. 4 illustrates an example of AI / ML framework for CSI feedback. Artificial Intelligence and / or Machine Learning (AI / ML) based CSI feedback may use autoencoders (AE) for CSI compression; this is a two-sided system, where the estimated CSI is compressed at the WTRU side, fed back to the base station, and then decompressed at the base station. One advantage of AI / ML based CSI compression may be performance improvement compared to legacy CSI feedback using a similar payload size. However, a disadvantage of AI / ML based CSI feedback may be the compression error that may occasionally lead to significant mismatch between the precoder computed at the WTRU and decompressed precoder at the network side (e.g., base station), X and X’.

[0076] From the illustration of FIG. 4 an example of AI / ML framework for CSI feedback may be better understood. For this example, there may be an encoder 401 (e.g., a WTRU) and a decoder 403 (e.g . , a network entity, such a base station, or other entity as described herein). As shown, there may be input X that is encoded to Y, which is feedback 402 for reporting. When the feedback in the compressed form Y is received, it may be decoded to generate X’ by decoder 403. While the encoder is shown to be a WTRU and the decoder a network, it may be understood that these may be any entities capable of exchanging CSI information (e.g., CSI-RS, CSI-reports, etc.).

[0077] In some cases, in multi-TRP scenarios a WTRU may access more than one TRP simultaneously. CSI Compression may be used by utilizing one or more mechanisms and / or methods for AI / ML-based compression and feedback of a channel matrix.

[0078] Generally, multi-TRP communications require the feedback of multiple channel states to the network. Especially, for CJT, the accuracy of the reconstructed channel matrices at the network may be important. Accordingly, there is a need for efficient mechanisms to address the transmission errors and mismatches for AI / ML-based CSI feedback.

[0079] The channel matrices of TRPs measured by the WTRU may be compressed jointly to improve the compression rate and reduce CSI feedback overhead. However, there is a need for one or more mechanisms and / or methods for the determination and reporting of AI / ML-based joint or separate compression of the multiple channel matrices.

[0080] In some cases, the WTRU may fall back to legacy CSI reporting from AI / ML-based CSI compression. In such a case, there is a need for mechanisms for fallback to legacy CSI reporting for AI / ML-based multi-TRP CSI compression.

[0081] Although the collection of the local CSI may be sufficient to perform NCJT across TRPs, for CJT, additional co-phasing component may be needed to adjust phase mismatch across CSI-RS from different TRPs. There is a need for AI / ML-based feedback of co-phasing.

[0082] In order to address handling CSI compression issues in multi-TRP, such as those described herein and others, there is a need for one or more techniques. For example, one or more techniques described herein may improve the reliability of AI / ML-based CSI feedback in mTRP to address transmission errors and mismatch. For example, one or more techniques described herein may determine and indicate joint or separate compression for AI / ML-based CSI compression in mTRP. For example, one or more techniques described herein may determine and indicate fallback to legacy CSI report for AI / ML-based CSI compression in mTRP. For example, one or more techniques described herein may feedback the co-phasing via AI / ML-based compression.

[0083] As described herein, CSI compression may refer to the use of an AI / ML model for the compression of a channel matrix or a processed channel matrix.

[0084] A CSI compression type may be joint or separate, where joint refers to jointly compressing the CSI (e.g ., channel matrix or eigenvectors) of a set (e.g. , more than one) WTRU-to-TRP links, and separate refers to compressing the CSI feedback individually per each WTRU-to-TRP link.

[0085] As described herein, Multi-TRP (mTRP) may refer to the use of more than one TRPs simultaneously for a WTRU’s downlink or uplink communication.

[0086] As described herein, linear coding may refer to the operation of computing linear combination(s) of vectors or matrices based on the real values coefficients in a linear coding matrix.

[0087] As described herein, interim matrix may refer to the linear combinations of vectors or matrices.

[0088] As described herein, mismatch may refer to a difference (e.g., a significant difference) between the input of an autoencoder at the WTRU side and the output of the autoencoder at the network side (e.g., that may degrade the performance of communication between the WTRU and network).

[0089] The terms channel matrix and channel response matrix may be used interchangeably herein.

[0090] Co-phasing or phase offset may refer to the additional CSI component that comprises the phase offset between different TRPs.

[0091] Fallback as described herein may refer to the use of legacy CSI reporting techniques rather than AI / ML based techniques.

[0092] Generally, techniques and approaches for dealing with issues with CSI compressing in multi-TRP communications may have one or more benefits.

[0093] For example, a first set of benefits may include improved resilience to the mismatch and transmissions errors by introducing linear coded CSI compression and decompression of channel matrices. In this approach the additional CSI reports decrease the mismatch between input and output of the CSI compression / decompression mechanisms. Moreover, the additional CSI reports help recover any lost or incorrectly decoded CSI reports in case of transmissions errors.

[0094] For example, a second set of benefits may include more efficient compression and feedback of CSI via introducing joint compression of channel matrices from different TRPs. In this approach the WTRU may group the channel matrices according to their correlation level and compress the correlated matrices jointly to reduce the CSI feedback overhead.

[0095] For example, a third set of benefits may include efficient mechanisms for fallback to legacy operation. In this approach, the WTRU may get indication or determine to fallback to legacy operation to prevent a significant performance degradation or to meet certain criteria for the efficient operation of CSI reporting.

[0096] In some cases, there may be linear coded SCI compression for mTRP.

[0097] A WTRU may receive configuration for linear coded CSI compression for mTRP.

[0098] The WTRU may receive configuration information (e.g., in one or more messages via DCI, MAC CE or RRC) to perform linear coded CSI compression. The configuration information may include information about one or more parameters.

[0099] For example, configuration information may include a set of linear coding matrices. The WTRU may receive a set (codebook) of linear coding matrices to select a linear coding matrix. The WTRU may compute new matrices using the measured channel matrices of TRP-to-WTRU connections and the selected linear coding matrix.

[0100] For example, configuration information may include a number of TRPs (e.g., M). The WTRU may receive the number of TRPs and determines the number of channel measurements and CSI reports. The number of TRPs determines the dimension of linear coding matrix.

[0101] For example, configuration information may include priorities of TRP-to-WTRU connections. The TRP-to-WTRU links may be assigned priorities by the NW. If the WTRU receives priorities of TRP-to-WTRU links, the WTRU may determine the linear coding matrix based on the priorities.

[0102] For example, configuration information may include a number of compressed CSI feedback messages (e.g., M+k, or only k where M is already known). This parameter may have more than one approach, which may depend on one or more factors described herein. The WTRU may receive the number of additional feedback messages, k, and use this information to determine the dimension of linear coding matrix. In one case, M may be already configured or known, hence only k need be configured. In one case, a WTRU may determine K based on one or more p

[0103] Alternatively, configuration information may indicate the WTRU to determine and report the number of additional CSI feedback messages, k, where the indication may include one or more additional parameters. For example,

[0104] For example, an additional parameter may be an initial value for k. The WTRU may receive an initial value of k as the initial value of k in an iterative process to determine k.

[0105] For example, an additional parameter may be a threshold for k (e.g., max / min value for k). The WTRU may receive a threshold for k (maximum value for k) to be used in the process to determine the value of k.

[0106] For example, an additional parameter may be a threshold for the total feedback overhead (e.g., maximum overhead). If the WTRU receives a threshold on the total CSI feedback overhead, then the WTRU may use the threshold to determine the value of k.

[0107] For example, an additional parameter may be a threshold on block error rate. If the WTRU receives a threshold on block error rate, then the WTRU may determine the value of k to satisfy the target block error rate.

[0108] For example, an additional parameter may be a threshold on mismatch. The mismatch may be defined by a metric measuring the similarity of input and output of an autoencoder, such as cosine similarity or mean squared error. If the WTRU receives a threshold on mismatch, then the WTRU may determine the value of k and the linear coding matrix to satisfy the target mismatch.

[0109] For example, an additional parameter may be a threshold on the difference of statistical distributions. If the WTRU receives, a threshold on the difference of statistical distributions, then the WTRU may determine the value of k and the of linear coding matrix based on this threshold.

[0110] The WTRU may have one or more procedures for linear coded CSI compression for mTRP.

[0111] FIG. 5 illustrates an example of linear coded CSI compression mechanism for mTRP with separate encoder / decoder (option-a).

[0112] From the illustration of FIG. 5 mechanisms for linear coded CSI compression may be better understood. For this example, there may be a WTRU 501 and a network entity 505 (e.g., base station, TRP, etc.). The WTRU 501 may utilize an encoder (e.g., multiple, such as 503 and 504) for each CSI report. Reciprocally, the network entity 505 may have a decoder (e.g., multiple, such as 506 and 507) for each CSI report. In some instances, there may be a CSI report for each WTRU-to-TRP link. In some instances, there may be additional number of CSI reports (e.g., configured or determined k).

[0113] FIG. 6 illustrates an example of linear coded joint CSI compression mechanism for mTRP with joint (e.g., single) encoder / decoder (option-b).

[0114] From the illustration of FIG. 6 mechanisms for linear coded CSI compression may be better understood. For this example, there may be a WTRU 601 and a network entity 604 (e.g., base station, TRP, etc.). The WTRU 601 may utilize an encoder (e.g., one, such as 603) for all CSI reports. Reciprocally, the network entity 604 may have a decoder (e.g., one, such as 605) for all CSI reports. In some instances, there may be a CSI report for each WTRU-to-TRP link. In some instances, there may be additional number of CSI reports (e.g., configured or determined k).

[0115] A high-level representation of the linear coded CSI compression mechanism for mTRP with separate encoder / decoders (option-a) is provided in FIG. 5, where Hm, m = l-. M represents channel matrix of mth TRP-to-WTRU link, Xn, n = 1: N represents the interim channel matrices(e.g., processed channel matrices of linear combinations of channel matrices), Yn, n = l-. N represents the compressed interim channel matrices, Xn, n = l-. N represents the decompressed interim matrices and Hm, m = 1: M represents recovered channel matrices. The WTRU computes interim matrices Xn, n = 1: N (e.g., linear combinations of channel matrices) as a function of channel matrices Hm, m = 1: M and a linear coding matrix AMXN= [ai7] where N = M + k . Here k represents the additional number of CSI reports (e.g., additional to M). In one instance for option (a), the WTRU may use parallel encoders, and / or in another instance for option (a), the WTRU may reuse a single encoder sequentially to compress X±, ... , XN. A high-level representation of the linear coded joint CSI compression mechanism for mTRP with single (e.g., joint) encoder / decoder (option-b) is provided in FIG. 6, where the WTRU generates a single compressed CSI report Y.

[0116] For an example, in one procedure, a WTRU receives CSI-RS from each TRP and estimates the channel matrix of each TRP-to-WTRU link using CSI-RS refence signals.

[0117] Then, the WTRU initiates the process to determine a linear coding matrix AMXN= [ai7] where N = M + k, and where k is an integer greater to or equal to 0. The WTRU may be configured with a set of linear coding matrices where each linear coding matrix in the set would be specific to a certain number of TRPs, a certain number of additional CSI reports k and a certain scenario.

[0118] The process to determine the linear coding matrix may include a first part where the WTRU determines the number of additional CSI feedback, k. In one case, the WTRU may receive an indication of the number of additional CSI feedback k (e.g., network configured k). In another case, the WTRU may receive an indication to determine k based on configured on one or more additional parameters, as disclosed herein (e.g., the network would not indicate the number of additional CSI feedback k, but may indicate one or more parameters that could help in determining k). In one case, the one or more additional parameters may be determined from the WTRU, and / or indicated by the network indirectly or directly. For example, the WTRU may determine k based on historical average block error rate of the transmission of CSI reports and initial value for k. If the historical average block error rate exceeds the configured threshold, then the WTRU may increase k by 1 . As another example, the WTRU may determine k based on the historical mismatch metric. If the historical average mismatch (e.g., measured by cosine similarity of input and output of the autoencoder) exceeds the configured threshold, then the WTRU may increment k by 1. In another case, the WTRU may determine k based on the configured threshold on k. The WTRU may stop incrementing k when the threshold on the value of k is reached. In another case, the WTRU may determine k based on the configured threshold on total feedback overhead. The WTRU may limit k such that the total number CSI feedback including the k additional CSI reports is below the configured threshold.

[0119] The process to determine the linear coding matrix may include a second part where, after determining k, the WTRU determines the elements of the linear coding matrix. In one case, the elements of the linear coding matrix can be determined based on the estimated mismatch metric of the inputs to the encoder at the WTRU. For example, if the distribution of a channel matrix Hnis significantly different than the distribution of the data used for the training (e.g., the difference being higher than the configured threshold), then the WTRU may allocate a higher value to the elements in the linear coding matrix corresponding to the channel matrix Hn. As another example, if the WTRU is equipped with a proxy decoder, then the WTRU may estimate the mismatch between input and output channel matrix Hn(e.g., cosine similarity), and if the mismatch exceeds the mismatch threshold, then the WTRU may allocate a higher value to the elements in the linear coding matrix corresponding to the channel matrix Hn. As another example, the WTRU may determine the elements of the linear coding matrix based on the configured priorities of TRP-to-WTRU links. In one case, the values of the elements may be determined as a function of the mismatch, or statistical difference or priorities, per Hn.

[0120] After determining the linear coding matrixthe WTRU computes the interim matrices Xnas shown below.

[0121]

[0122] Another representation of the computation on interim matrices is provided below for M = 3, N = 4.

[0123]

[0124] Finally, in the case of option-a (e.g., separate compression) the interim matrices Xn, n =1: N may be provided as input to the encoder for separate compression to generate N = M + k compressed CSI reports. In case of option-b (e.g., joint compression), the interim matrices Xn, n = 1: N may be provided as input to the encoder for joint compression to generate a single compressed CSI report.

[0125] The WTRU may send feedback and / or CSI report(s) for linear coded CSI compression.

[0126] The WTRU may send one or more reports after determining the linear coding matrix and compressing the CSI feedback using autoencoders.

[0127] For example, the WTRU may report the determined linear coding matrix. The WTRU may report an index from the set (e.g., codebook) of configured linear coding matrices. The indexrepresents a linear coding matrix that the network can use for the post-processing to recover the original channel matrices. The index may occupy a fixed number of bits determined according to the size of the set (e.g codebook) of linear coding matrices. For example, if the size of the set is 64, then the feedback on the index of determined linear coding matrix may occupy 8 bits. Add itionally / alternatively , the WTRU may directly report the values of the linear coding matrix without using an index to a codebook.

[0128] For example, the WTRU may report a number of additional CSI feedback reports. The WTRU may report the number of additional CSI feedback reports, if configured by the network. The report on the number of CSI feedback reports may occupy a fixed number of bits determined according to the maximum allowed value of k. For example, if the maximum allowed value of k is 7, then the feedback on the determined k may occupy 3 bits.

[0129] For example, the WTRU may feedback the compressed CSI reports. In case of option-a, the WTRU reports M+k compressed interim matrices, which are obtained by the linear combinations of M channel matrices according to the linear coding matrix. In case of option-b, the WTRU reports a single compressed CSI report obtained by jointly compressing the M+k interim matrices.

[0130] For example, the WTRU may report, optionally, if the TRPs have non-ideal backhaul, the timestamps of received CSI-RS to network for scheduling purposes.

[0131] The reporting of the determined linear coding matrix and number of additional CSI reports may be configured semi-statically via RRC, or more dynamically via MAC CE and / or DCI signaling. The reporting of the compressed CSI reports may be configured dynamically via MAC CE and / or DCI signaling.

[0132] As may be understood from FIGs. 5 and 6 and the related description, a WTRU may compute: channel matrices Hm, 1 < m < M for all TRPs (e.g., where M is the number of TRMs, and m is an index between 1 to M); linear coding matrix AMXN\ and / or, interim channel matrices Xn(N > M) as a function of Hmand AMXN. The WTRU may feedback compressed interim channel matrices Yn, 1 < n < N and AMXN. The compressed CSI feedback Yn (n between 1 and N) can be feedback in a single report or multiple CSI reports. A network entity may recover Hmas a function of 4MxWand decompressed Xn. If some Ynis missing, the network entity may still recover Hm(e.g., based on one or more approaches described herein, such as but not limited to the following example).

[0133] In one example, CSI feedback is generated at the WTRU for linear coded CSI compression for mTRP. This example illustrates the case where the number of TRPs is given by M = 3 and the total number of CSI reports is given by N = M + k = 4 for k = 1, where k = 1 is configured by the network.

[0134] For this example, it may be assumed that the WTRU received configuration to select the matrix A from the set

[0135]

[0136] The WTRU computes the interim matrices as a function of A and channel matrices

[0138] Example computations for interim matrices are provided below.

[0139] For A = A4(which can be chosen if WTRU estimates similar mismatch for the channel matrices or NW assigns equal priority) the interim matrices may be computed as follows.

[0154] The WTRU compresses the interim matrices using the encoder of autoencoder and obtains compressed CSI reports,

[0155] At the network, the CSI may be reconstructed. When all 4 CSI feedback isreceived by the network for option-a, or Y successfully received for option-b, the network may decompress the feedback using the decoder of autoencoder and obtains the reconstructed interim matrices X

[0156] Then the network may reconstruct the channel matricesH2, H3, as an example, using the pseudo-inverse of A and X

[0157]

[0158] where A+is the pseudo-inverse of A.

[0159] For demonstration, it may be assumed that the recovered interim matrix has a mismatch based on a Gaussian noise. Let Xt= Xt+ n, where n~ / V(0, / z). If may be assumed that the channel matrices are selected from a Gaussian Normal distribution, ~ / V(0,l).

[0160] Normalized mean squared error (NMSE) performance of the reconstructed channel matrices for different A are given in Table 1 and Table 2. In Table 1 , the mismatch is similar for all interim matrices, such that Xt= Xt+ n, where n~N (0,0.01). Whereas in Table 2, the mismatch is higher for Xrsuch that X±= X1+ n , where n~N (0,0.04) , and Xt= Xt+ n , where n~N (0,0.01) for i #= 1. Direct decode in both tables refer to directly using Xt, X2and X3to recover H\, H2, H3discarding the additional interim matrix X4.

[0161] The results in Table 1 show that using X4besides Xt, X2and X3improves NMSE. In addition, by selecting higher coefficients in the linear coding matrix A corresponding to a certain channel matrix, the NMSE of the certain channel matrix can be further improved. For example, if the WTRU is configured with high priority for the compression of channel matrixthen the WTRU may choose A3to improve the NMSE performance of recovered channel matrix H1at the network.

[0162] The results in Table 2 show that the additional interim matrix X4can improve the NMSE performance especially if the coefficients of linear coding matrix A are properly chosen. For example, if the WTRU estimates higher mismatch in the recovery of H4, compared to other channel matrices, then using the linear coding matrix A3will results in significantly better NMSE results compared to direct decode.Table 1 : NMSE (dB) results for similar mismatch on interim matricesTable 2: NMSE (dB) results for different mismatch on interim matrices

[0163] When one feedback is missing (e.g., applicable to option-a) out of Yl tY2, Y3, Y4, the received subset of YltY2, Y3, Y4can be used to reconstruct H4, H2, H3.

[0164] Assuming that Y4is not received successfully (e.g., CRC failed), then the network may only reconstruct X2, X3and X4. Given that the network decompresses and obtains X2, X3and X4, the network may reconstruct channel matrices as follows.

[0166] where A1denotes the inverse of A and A(2: 4, : ) denotes a matrix constructed using the 2ndto 4throws of linear coding matrix A.

[0167] NMSE performance of the reconstructed channel matrices for different A, when first feedback message is lost, is given in Table 3 where the mismatch is similar for all interim matrices, such that X In this case, as Y4is not receivedsuccessfully, direct decode method cannot recover / ?!. If the proposed solution is used, all channel matrices can be recovered where H\ may experience NMSE performance degradation compared to other channel matrices, and degradation depends on the selected linear coding matrix. If the WTRU determines to use the linear coding matrix A3, then the NMSE degradation becomes lower.Table 3: NMSE (dB) results for similar mismatch on interim matrices in case first feedback message is lost

[0168] In one example, a WTRU may be configured with linear coded CSI compression for mTRP. The WTRU may perform one or more steps, such as estimate M channels from M TRPs, determine a linear coding matrix of size (M + k) x M , compute M + k linear combinations of channel matrices according to the determined linear coding matrix, compress M + k linear combinations, and / or feedback k, the determined linear coding matrix, and one or more compressed CSI reports.

[0169] The WTRU may receive configuration information in one or more messages to perform linear coded CSI compression. The configuration information may include one or more ofthe following: set of linear coding matrices; number of TRPs (e.g . , M); priorities of TRP-to-WTRU links; number of compressed CSI feedback reports (e.g., M + k). In another example, the WTRU may receive configuration to determine k, where the WTRU may receive (e.g., additional) configuration information on: an initial value for k\ the threshold for the number of compressed CSI feedback reports (M + k)\ the threshold for the total feedback overhead; threshold on block error rate; threshold on mismatch, where mismatch may be defined by a metric measuring the similarity of input and output of an autoencoder, such as cosine similarity or mean squared error; and / or, threshold on the difference of statistical distributions

[0170] The WTRU may receive CSI-RS, and measure the channel response of each TRP-to- WTRU link using CSI-RS reference signals, for a total of M channel response matrices.

[0171] The WTRU may determine the number of additional CSI feedback, k, in one or more ways. In one instance, the WTRU may determine k based on the historical reliability of previously transmitted CSI reports. For example, if the historical average block error rate of the transmission of CSI reports exceeds the configured threshold, then the WTRU may increment k. In one instance, the WTRU may determine k according to historical mismatch performance. For example, if the historical average mismatch of the autoencoder exceeds the configured threshold, then the WTRU may increment k. In one instance, the WTRU may limit the number of additional CSI feedback k accordingto the configured threshold for k or the threshold on total feedback overhead. In one instance, the WTRU may be indicated with the number of additional CSI feedback k by the network.

[0172] The WTRU may determine the linear coding matrix to use based on one or more of the following: the number of TRPs; the priorities of the TRP-to-WTRU links; the estimated mismatch metric; and / or, the statistical distribution of channel matrices (e.g. , compared to the data used in training). For example, if the priority of the channel matrix is higher than another channel matrix, or if the estimated mismatch for a channel matrix is high (e.g., relative to a threshold or another channel matrix), or if the distribution of the channel matrix is significantly different (e.g., relative to a threshold or another channel matrix), then the corresponding channel matrix may be allocated with a higher coefficient (e.g., comparatively) in an additional CSI report.

[0173] The WTRU may compute M + k interim matrices (e.g., linear combinations of the M measured channel matrices) based on the determined linear coding matrix.

[0174] The WTRU may separately compress all interim matrices using an encoder of autoencoder (AE) to generate M + k compressed CSI reports.

[0175] Additionally / alternatively, the WTRU may jointly compress all interim matrices using a single encoder to generate a single compressed CSI report.

[0176] The WTRU may report (e.g., feedback information transmitted in one or more messages to the network) the determined linear coding matrix, the determined number of additional CSI feedback k, and one or more compressed CSI reports.

[0177] In some cases, a WTRU may determine joint or separate compression for AI / ML based CSI feedback. The WTRU may receive configuration information for making this determination.

[0178] The WTRU may be configured with an AI / ML model to support CSI compression for mTRP.

[0179] The WTRU may receive configuration to determine the type of CSI compression, such as separate or joint compression for TRPs. The determination of the compression type may be based on one or more metrics such as correlation between channel matrices, TRPs’ localization, the speed of the WTRU, and the like (e.g., as described herein).

[0180] The WTRU may compute the correlation between the channels to determine the joint or separate compression. The TRPs localization may help the WTRU to filter the uncorrelated TRPs depending on its own speed and location, wherein the WTRU may optionally identify line-of-sight (LOS) and non-line-of-sight (NLOS) between its current / future position and the TRPs. The speed of the WTRU may assist the WTRU to correct the correlation calculation considering the feedback delay, such as where the WTRU is in high-speed motion, wherein in an option, the WTRU may correct the correlations if its speed exceeds a pre-configured threshold. Optionally, the WTRU may receive anindication of the AI / ML decoder capabilities, such as the maximum number of supported joint compression / decompression. In this option, the WTRU may filter the subsets of correlated matrices accordingly based on the received configuration of the AI / ML model.

[0181] The WTRU may receive configuration information (e.g., related to the compression type and / or determining the compression type) via one or more DCI fields, which may include one or more of the following: one or many threshold values on the correlation between TRPs to WTRU channels; granularity of correlations, wherein the level of correlation may be calculated in full channel level or sub-channel level; location of the TRPs, wherein the exact localization may assist the WTRU to estimate the right level of correlation when the WTRU is moving with some speed; distance thresholds for TRPs to assist the WTRU in determining correlation between TRPs; a speed threshold, that may assist the WTRU to decide if further filtering of the subset is required; the AI / ML model capabilities, such as the number of supported joint compression / decompression inputs to be processed by the model; and / or, an indication of a specific type to perform that type of CSI compression (e.g., from the network).

[0182] A WTRU may determine a compression type for mTRP as described herein. One or more CSI compression types for mTRP operation may be used, determined, or configured to a WTRU, where: mTRP operation may imply that a WTRU reports CSI for one or more TRPs associated with a transmission or reception for the WTRU; a first CSI compression type may be a joint CSI compression of channel information of all TRPs (e.g., stacked channel matrix Hau), wherein the channel information may include but not be limited to channel matrix, processed channel information (e.g., eigen vectors, channel covariance matrices, implicit channel information such as PMI, Rl, CQI, L1-RSRP); a second compression type may be a joint CSI compression of channel information of a subset of TRPs (e.g., subset ofand / or, a third compression type may be a separateCSI compression of channel information of T

[0183] FIG. 7 illustrates an example of different compression types using autoencoder. There may be different compression types using autoencoder as illustrated. Here, Hnrepresents the channel matrix of TRP-n and H . As shown, there is an encoder 701 , the feedback (e.g . , generatedfrom the encoder) that is transmitted 702, and the decoder 703 which processes the feedback. Said another way, a CSI report may be compressed via the encoder and decompressed by the decoder in order to reduce the overhead of the CSI message.

[0184] As described herein, a joint CSI compression may be referred to as an AI / ML model which jointly compress channel information of multiple TRPs using a same encoder and channel informationof multiple TRPs may be reconstructed at the receiver with the same decoder. A separate compression may be referred to as an AI / ML model which compress channel information of one or more TRPs separately.

[0185] A Joint CSI compression may require less feedback overhead compared to separate CSI compression when channel information from one or more TRPs is correlated with the cost of complexity due to a larger AI / ML model.

[0186] A separate CSI compression may be a simpler AI / ML model (e.g., compared to joint compression) to encode / decode channel information individually per TRP and require lower complexity as compared with the joint CSI compression.

[0187] Possibly, there is a trade-off between complexity, feedback overhead, and CSI accuracy. Based on required complexity, feedback overhead, and CSI accuracy, a CSI compression type may be used.

[0188] In an example, a WTRU may determine CSI compression type based on measurements of one or more channel information, based on processed channel information, from one or more TRPs with one or more conditions. One example condition may be WTRU channel conditions including at least one of SINR level (e.g., based on last reported CQI), WTRU speed, accuracy level of the measurement, WTRU battery level. One example condition may be WTRU operation status including at least one of RRC status (e.g., RRC connected, RRC inactive, and RRC idle), power saving status (e.g., active time or sleep time), and number of WTRU panels active. One example condition may be channel information correlation level. One example condition may be uplink CSI reporting payload size.

[0189] For the condition regarding channel information correlation level, for example, a WTRU may correlate channel matrices from one or more TRPs, if the correlation level is higher than a threshold, the WTRU may determine a first CSI compression type (e.g., join compression); otherwise, the WTRU may determine a second CSI compression type (e.g., separate compression). The correlation level may be calculated or determined based on one or more considerations.

[0190] For example, one consideration may be a distance of two channel matrices from different TRPs, wherein the distance may be a matrix distance (e.g., correlation coefficient, chordal distance, cosign similarity, norm of matrix differences, Euclidean distance, etc.).

[0191] For example, one consideration may be a location of TRPs and the speed of WTRU may be used to adjust the correlation level. For example, if the WTRU speed is below the configured threshold and the distance of two TRPs is below the configured threshold, then the WTRU may group the two channel matrices in the same subset.

[0192] Alternatively, the distance may be calculated or determined based on processed matrix of the channel matrix (e.g eigenvectors, covariance matrix, averaged covariance matrix over multiple time / frequency resources) rather than using the channel matrix.

[0193] The threshold of the correlation level may be configured by a network to a WTRU. One or more of threshold values may be used if the number of CSI compression types are larger than 2.

[0194] For the condition regarding Uplink CSI reporting payload size, for example, a WTRU may determine CSI compression type based on the payload size for the CSI reporting. If the allocated or granted uplink payload size is smaller than a threshold, the WTRU may perform or determine a first CSI compression type (e.g., joint CSI compression); while if the payload size is larger than the threshold, the WTRU may perform or determine a second CSI compression type (e.g., separate CSI compression). The payload size may be determined based on one or more of: uplink resource type (PUCCH or PUSCH); number of RBs granted, allocated, or configured for the uplink resource; modulation order, number of layer, and / or coding rate for the uplink resource; and / or, bandwidth part (BWP), BWP-id, carrier, or carrier-ID associated with the reporting.

[0195] In an example, a WTRU may be indicated to perform one of the CSI compression type via one or more signals: AI / ML model pairing-ID; Transmission scheme; and / or, an explicit bit in DCI.

[0196] For example, one or more AI / ML model pairing-ID may be used and each AI / ML model pairing-ID may be associated with a CSI compression type. Based on the indicated AI / ML model pairing-ID, the WTRU may determine associated CSI compression type. Hereafter, AI / ML model pairing ID may be interchangeably used with AI / ML model ID, functionality ID, AI / ML model pair, AI / ML pair, AI / ML model pair of two-sided model.

[0197] For example, one or more transmission schemes may be used and each transmission scheme may be associated with a CSI reporting configuration, wherein each CSI reporting configuration may have a corresponding identity. A WTRU may be indicated with a CSI configuration identity, the WTRU may perform its associated CSI compression type.

[0198] For example, when a WTRU is triggered to report CSI, the WTRU may be indicated with a CSI compression in the associated DCI (e.g., one or more bits in the DCI) triggering the CSI report.

[0199] The WTRU may report the compression type of CSI reports for mTRP to the network. The WTRU may indicate whether joint compression of all channel matrices or processed channel matrices, subset based joint compression, or separate compression was performed at the WTRU. For example, the WTRU may use 2 bit fields in UCI to indicate the compression type.

[0200] For the joint compression of all channel matrices, the WTRU may feedback one CSI report composed of a single compressed (e.g., stacked) channel matrix to the network.

[0201] For the separate compression all channel matrices, the WTRU may feedback one or more CSI report(s) composed of multiple compressed channel matrices.

[0202] For the subset based joint compression of channel matrices, the WTRU may feedback one or more CSI report(s) constructed based on the determined subsets of channel matrices. The WTRU may also report information on the one or more determined subsets of channels such that the NW may reconstruct the channel matrices accordingly.

[0203] In an example, the WTRU may report one or more of the following: the number of subsets; identifiers (e.g., indices) of TRPs within each subset; and / or, information on the compression rate of each subset.

[0204] Optionally, if the TRPs have non-ideal backhaul, the WTRU may feedback the timestamps of received CSI-RS to the network for scheduling purposes.

[0205] The reporting of the determined compression type and information on the subsets for joint compression may be configured semi-statically via RRC, or more dynamically via MAC CE, and / or DCI signaling.

[0206] In one example, a WTRU may be configured with CSI compression for mTRP. The WTRI may perform one or more actions, such as: receive CSI-RS and estimate channel matrices for TRPs, determine a subset of channel matrices, or subchannels or processed channel matrices, for joint compression according to a metric such as correlation, compress the channels in the subset jointly, compress the channels not in the determined subset separately, and / or feedback the compressed CSI reports and information on subsets.

[0207] The WTRU may receive configuration information to determine type of compression, joint or separate for TRPs, in one or more messages. The configuration information may include one or more of the following: thresholds on correlation between TRP to WTRU channels; granularity of correlation, such as full channel or subchannel level correlation; distance thresholds for TRPs to assist the WTRU in determining correlation between TRPs; and / or, speed threshold, that may assist the WTRU to decide on the compression type.

[0208] The WTRU may receive CSI-RS and measure the channel for each TRP (M TRPs).

[0209] The WTRU may compute a correlation between different TRP to WTRU channel matrices, or processed channel matrices.

[0210] The WTRU may determine a CSI compression type for mTRP operation. If the correlation level is above a threshold, the WTRU may compress all the CSI jointly (e.g., Haa), using an AI / ML model once. If the correlation is below a threshold, the WTRU may compress each CSI separately (e.g., Hn) using an AI / ML model M times. The WTRU may compute the correlation matrix of one ormore subchannel(s) for one or more TRP to WTRU channels. The WTRU may determine one or more subset(s) of channel matrices and / or subchannels according to the correlation matrix, for which joint compression is applicable (e.g., subset of {Hr, and compresses each of the one or more determined subset(s) using joint compression (e.g., using an AI / ML model). The WTRU may compress each of the other subchannels and / or channels (e.g., not in the determined subset(s)) separately.

[0211] The WTRU may send a feedback indication regarding whether joint or separate compression was used in one or more messages. The WTRU may send information (e.g., feedback), in one or more messages, on the one or more determined subsets of channels and / or subchannels and compressed CSI (e.g., one or more jointly compressed CSI and one or more separately compressed CSI).

[0212] In some cases, a WTRU may determine to fallback to codebook-based CSI feedback for mTRP (e.g., as opposed to AI / ML compression CSI).

[0213] The WTRU may be configured with one or more behavior(s) associated with fallback to codebook-based CSI feedback for multi-TRP reporting. In an example, the WTRU may be configured with rules / conditions to fallback to codebook-based CSI feedback when operating in joint compression mode. In an example, the WTRU may be configured with rules / conditions to fallback to codebookbased CSI feedback when operating in AI / ML based co-phasing compression. In an example, the WTRU may be configured with rules / conditions to fallback to codebook-based CSI feedback when operating in joint and / or separate compression. Possibly, the rules / conditions may be a function of current CSI compression mode. As described herein, the terms codebook-based CSI feedback and legacy CSI feedback may be used interchangeably.

[0214] In one case, the WTRU may be configured with one or more parameters associated with fallback to codebook-based CSI feedback for multi-TRP.

[0215] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of number of antennas per TRP. For example, the WTRU may be configured with a threshold associated with number of antennas per TRP. For example, the WTRU may be configured to fallback to codebook-based CSI feedback when the number of antennas per TRP falls below the configured threshold. For example, the WTRU may be configured to fallback to codebook-based CSI feedback when the number of antennas in the TRP (e.g., the TRP with lowest number of antennas among the TRPs configured for multi-TRP operation), falls below the configured threshold.

[0216] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of A number of TRPs. For example, the WTRU may be configured with a threshold associated with number of TRPs applicable for multi-TRP reporting. For example, the WTRU may beconfigured to fallback to codebook-based CSI feedback when the number of TRPs falls below the configured threshold.

[0217] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of performance gains associated with linear coded compression and / or co-phasing compression. Possibly, such performance gains may be derived based on intermediate KPIs like SGCS, NMSE, phase quantization loss, etc. For example, the WTRU may be configured with a threshold associated with SGCS. For example, the WTRU may be configured to fallback to codebookbased CSI feedback when the SGCS associated with joint compression falls below the configured threshold. For example, the WTRU may be configured with a threshold associated with NMSE. For example, the WTRU may be configured to fallback to codebook-based CSI feedback when the NMSE associated with joint compression exceeds the configured threshold. For example, the WTRU may be configured with a threshold associated with phase quantization loss. For example, the WTRU may be configured to fallback to codebook-based CSI feedback when the phase quantization loss associated with joint compression exceeds the configured threshold.

[0218] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of reporting overhead. For example, the WTRU may be configured with a threshold associated with reporting overhead. Possibly, such reporting overhead may be derived based on the number of payload bits required for CSI feedback. For example, the WTRU may be configured to fallback to codebook-based CSI feedback when the overhead associated with joint compression becomes above the configured threshold.

[0219] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of configured reporting resources. For example, the WTRU may be configured with different reporting resources. Possibly, different reporting resources may be associated with different payload sizes, periodicities, reliability etc. In one instance, each reporting resource may be associated with different CSI reporting method. For example, the WTRU may be configured to fallback to codebookbased CSI feedback when the triggered CSI feedback is for a CSI reporting resource which is associated with codebook-based CSI feedback.

[0220] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback upon receiving implicit or explicit indication from the network. For example, an explicit indication may be carried in a DCI. For example, such explicit indication may be an aperiodic CSI request.

[0221] In one case, the WTRU may be configured to fallback to codebook-based CSI feedback as a function of applicable conditions preconfigured for the AI / ML model used for joint compression and / or co-phasing compression. For example, the applicable condition may be configured as one ormore of: base station, cell, area, groups of TRPs, carrier frequency, bandwidth, BWP, RSRP, SNR, SINR, CQI, antenna port layout, model ID, pairing ID etc. For example, the WTRU may be configured to monitor a change in applicable condition. For example, the WTRU may be configured to select the CSI feedback mechanism based on the observed applicable condition. Possibly such selection include fallback to codebook-based CSI feedback when the observed condition doesn’t match the applicable condition configured for joint compression and / or co-phasing compression.

[0222] The WTRU may determine to fall back to legacy (e.g., non AI / ML procedures) based on conditions no longer being met. Such conditions may relate to a context where an AI / ML model ‘applicable’ in one scenario is no longer applicable in another scenario. The AI / ML model may include any one or more of the following: autoencoder(s) at the WTRU for CSI compression, autoencoder(s) at the WTRU for compressing the co-phasing information, and / or corresponding decoder at the base station (e.g., for reconstructing the CSI). There may be one or more conditions that may result in the WTRU falling back to legacy mechanisms, as described herein.

[0223] For example, one condition may be WTRU internal conditions (e.g., computational / processing capability, memory, battery, storage capability, etc.). For example, WTRU may determine a subset of TRPs to fallback to legacy CSI feedback based on availability of WTRU computation resources.

[0224] For example, one condition may be TRP conditions / configurations. For example, a WTRU may fallback to legacy CSI feedback for a TRP when the number of antennas of a TRP falls below a threshold. For example, a WTRU may fallback to legacy mTRP codebook based CSI feedback when the number of TRPs is smaller than a threshold.

[0225] For example, one condition may be a configuration a WTRU receives from the network, for example, including any of the conditions mentioned herein.

[0226] For example, one condition may be an indication / command a WTRU receives from the network to switch to legacy CSI compression.

[0227] For example, one condition may be related to performance monitoring. For example, a WTRU may monitor the estimated the performance gains (e.g., in terms of CQI, PMI, Rl, SNR, SINR, throughput) for each TRP and decides fallback accordingly. For example, the WTRU may use a proxy AI / ML decoder per TRP. In one instance, if WTRU detects performance degradation for at least one of the TRPs then WTRU may fallback to legacy CSI report for at least the concerned TRP.

[0228] For example, one condition may be the quantization loss of legacy co-phasing reporting. For example, if the quantization loss of the legacy co-phasing reporting is below a threshold, then the WTRU may determine to fall back to legacy co-phasing reporting (e.g., to save computation power).

[0229] For example, one condition may be dependencies between the two or more autoencoders at the WTRU. For example, the WTRU may have more than one AE. For example, one is for compressing CSI and another for compressing the co-phasing. The WTRU may determine fallback to legacy jointly. In one instance, if the WTRU determines, or gets an indication, to fallback to legacy CSI reporting, this may trigger fallback to legacy co-phasing reporting. In one instance, if the WTRU determines, or gets an indication, to fallback to legacy co-phasing reporting, this may trigger fallback to legacy CSI reporting

[0230] For example, one condition may be training applicability. For example, the WTRU may be moving and the set of conditions (e.g . , new cell / radio conditions) following WTRU movement may no longer match the set of parameters that the AI / ML model at the WTRU was trained on.

[0231] For example, one condition may be certain scenarios (e.g., channel conditions, WTRU distribution, WTRU mobility levels, carrier frequencies, etc.). If measured RSRP with regard to a TRP is below a preconfigured threshold, WTRU may fall back to legacy mechanisms.

[0232] For example, one condition may be certain configurations (e.g., WTRU / base station / TRP config, bandwidths, antenna port layouts).

[0233] For example, one condition may be certain sites. For example, training may not have accounted for certain sites / deployments. Deploying the model in sites where it may not have been trained may result in poor performance of the mode.

[0234] For example, one condition may be a loss of synchronization between autoencoder and corresponding decoder at TRP.

[0235] Based on any one or more of the conditions described herein, the WTRU may determine whether to fallback to legacy CSI compression procedures, to fallback to legacy CSI compression procedures for all or a subset of TRPs, the number and / or identity of the TRPs for which to fallback to legacy CSI compression procedures, whether the fallback to legacy procedures is a one-shot event or lasts for some time duration or lasts indefinitely or last until an event triggered (e.g., if the quantization loss of the legacy co-phasing reporting exceeds the preconfigured threshold, the WTRU may revert to AI / ML mechanisms).

[0236] Upon fallback to codebook-based feedback (e.g., based on one or more examples described herein), the WTRU may determine the CSI feedback based on preconfigured codebook. The WTRU may transmit the CSI feedback according to the parameters configured for codebookbased CSI feedback. The WTRU may be configured to indicate explicitly or implicitly the type of CSI feedback contained the CSI report. For example, upon fallback to codebook-based CSI feedback, the WTRU may transmit an indication in the CSI report that the format of CSI report corresponds tocodebook-based CSI feedback. For example, the WTRU may indicate the type of CSI feedback in a first CSI part and the actual CSI feedback in the second CSI part. Possibly the WTRU may indicate in the first CSI part that the CSI feedback in the second part is based on codebook-based CSI feedback. In one instance, the indication may be implicit. For example, the WTRU may be configured with a first reporting resource and a second reporting resource. For example, the first reporting resource may be associated with joint compression and / or co-phasing compression. For example, the second reporting resource may be associated with codebook-based compression. The WTRU may implicitly indicate that the codebook-based CSI feedback based on selection / transmission of CSI feedback on the second reporting resource.

[0237] In one example, a WTRU configured with CSI compression for mTRP, receives CSI-RS and estimates channel matrices for TRPs, determines to fallback to legacy CSI reporting based on configured parameters, and / or feeds back CSI reports and information on fallback per TRP.

[0238] The WTRU may receive configuration information (e.g., in one or more messages) regarding one or more parameters for fallback to legacy CSI and legacy co-phasing reporting for m- TRP CSI compression. The one or more parameters may include: threshold on number of antennas per TRP; threshold on number of TRPs; thresholds on performance gains; and / or, threshold on cophasing quantization loss.

[0239] The WTRU may receive CSI-RS and measure the channel for each TRP.

[0240] The WTRU may determine the type of CSI feedback for TRPs.

[0241] The WTRU may fallback to legacy CSI feedback for a TRP when the number of antennas of a TRP falls below a threshold.

[0242] The WTRU may determine a subset of TRPs to fallback to legacy CSI feedback based on availability of WTRU computation resources.

[0243] The WTRU may fallback to legacy mTRP codebook based CSI feedback when the number of TRPs is smaller than a threshold.

[0244] The WTRU may monitor the estimated the performance gains (e.g., in terms of CQI, SNR, throughput) for each TRP and decides fallback accordingly. For example WTRU may use a proxy AI / ML decoder per TRP. In one instance, if WTRU detects performance degradation for at least one of the TRPs then WTRU may fallback to legacy CSI report for TRPs. In another instance, WTRU may determine fallback on a per TRP basis.

[0245] If the quantization loss of the legacy co-phasing reporting is below a threshold, then the WTRU may determine fallback to legacy co-phasing reporting (e.g., to save computation power).

[0246] The WTRU may have more than one AE. For example, one is for compressing CSI and another for compressing the co-phasing. The WTRU may determine fallback to legacy jointly. In one instance, if the WTRU determines, or receives an indication, to fallback to legacy CSI reporting, this may trigger fallback to legacy co-phasing reporting. In one instance, if the WTRU determines, or receives an indication, to fallback to legacy co-phasing reporting, this may trigger fallback to legacy CSI reporting.

[0247] The WTRU may send a message (e.g. , feedback) the determined type of CSI feedback for TRPs and CSI reports generated using the determined type of CSI feedback for TRPs.

[0248] In some cases, a WTRU may perform AI / ML based co-phasing compression.

[0249] A WTRU may be configured with co-phasing report compression. The configuration may include one or more of: set of co-phasing representation type, anchor TRP determination type, reconstruction accuracy parameters (e.g., reconstruction accuracy type or threshold or target accuracy), and / or feedback overhead.

[0250] The WTRU may be configured with or may determine a reconstruction accuracy or a parameter thereof. The reconstruction accuracy may be compared to a target accuracy or a threshold. The target accuracy or threshold may be determined based on one or more of: indication from the base station (e.g., via DCI, MAC-CE or RRC); transmission type (e.g., the WTRU may determine the target accuracy based on an associated transmission type, where a transmission type may include at least one of: reliability, latency, priority, SRB, DRB, LCH, etc.); RS type (e.g., the WTRU may determine the target accuracy based on a TRP’s RS type or RS parameters, such as RS pattern, density, periodicity, configuration, etc.); anchor TRP; phase representation type; feedback overhead (e.g., a WTRU may determine the target accuracy based on the available feedback overhead for a feedback report) ;and / or, performance of previous transmission (e.g., associated transmission) (e.g., based on a calculated rate of HARQ-ACKs, the WTRU may determine a target accuracy, such as if the rate of HARQ-ACKs is lower than a value, the WTRU may increase the target accuracy).

[0251] The WTRU may determine the reconstruction accuracy by using a proxy decoder to process the encoded feedback. The WTRU may predict a reconstruction accuracy based on channel measurements.

[0252] The WTRU may determine the feedback overhead based on at least one of: DCI indication, feedback channel (e.g., PUSCH or PUCCH or PSSCH), feedback resource, feedback timing, priority of feedback, and / or collision of feedback with other (higher, equal, or lower priority) feedback.

[0253] A WTRU may determine an anchor TRP from a group of TRPs. The anchor TRP may be used as a reference TRP from which all co-phase values in the group of TRPs may be determined.

[0254] A WTRU may determine multiple groups ofTRPs for which to provide feedback. The WTRU may determine an anchor TRP per group of TRPs.

[0255] The anchor TRP determination type may be base station-indicated or WTRU-determined. The WTRU may receive indication of anchor TRP from one or more of: DCI, RRC (re)configu ration, and / or MAC CE. The indication of anchor TRP may be received by one or more of: signaling for scheduling, feedback report configuration, and / or feedback report activation / deactivation.

[0256] The WTRU may determine the anchor TRP. The WTRU may indicate (e.g. , to the base station) the determined anchor TRP in a feedback report. The WTRU may determine or select a TRP to be an anchor TRP (e.g., for at least one feedback report) based on one or more factor.

[0257] For example, one factor may be TRP / cell / base station ID. For example, the WTRU selects the TRP with the highest or lowest ID to be the anchor TRP.

[0258] For example, one factor may be RS configuration associated with the TRP. For example, a WTRU selects a TRP to be an anchor TRP based on the RS type or pattern, periodicity, or density associated with the TRP.

[0259] For example, one factor may be timing. For example, the WTRU may be configured with, or may determine, an anchor TRP selection sweeping pattern. Based on at least one of: the timing of the feedback report or the TRP selection sweeping pattern, the WTRU may determine the TRP to use as anchor TRP. In another example, a WTRU may select a TRP to be an anchor TRP based on one or more of: the timing of the feedback request, measured RS of the TRP or of other TRPs, feedback report timing, and / or previous feedback report timing.

[0260] For example, one factor may be WTRU mobility parameters. For example, the WTRU may select an anchor TRP based on one or more of: its location, its speed, and / or its direction of movement.

[0261] For example, one factor may be measurements. For example, the WTRU may determine an anchor TRP based on a measurement on one or more RSs associated with one or more TRPs. The measurement may include one or more of: RSRP, CSI (e.g., Rl, CQI, PMI, LI, CRI), RSRQ, SINR, RSSI, Channel Occupancy, AoA, AoD, Doppler shift, Doppler spread, Delay spread, and / or average delay. In another example, the WTRU may select a TRP to be an anchor TRP based on co-phase measurements. In this example, the WTRU may determine co-phase measurements for multiple anchor TRP hypotheses and select an anchor TRP from the multiple anchor TRP hypotheses based on the co-phase measurements obtained. For example, the WTRU may select an anchor TRP such that the average or lowest or maximum phase difference is minimized or maximized or meets a threshold requirement.

[0262] For example, one factor may be previous feedback. For example, a WTRU may use a TRP as an anchor TRP based on a previous feedback or anchor TRP determination. A WTRU may determine an anchor TRP for a one or more feedback reports. For the case where the WTRU determines an anchor TRP for multiple feedback reports, the WTRU may report the selected anchor TRP in one feedback report and all other feedbacks in other feedback report may be associated with the indicated anchor TRP in the one feedback report.

[0263] For example, one factor may be associated transmission. For example, a WTRU may report feedback for a transmission of a type or associated with a set of transmission parameters (e.g ., reliability, latency, priority, etc.). Based on the associated transmission type or set of transmission parameters, the WTRU may determine or select a TRP as an anchor TRP.

[0264] For example, one factor may be reconstruction accuracy. For example, the WTRU may select a TRP, from a set of TRPS, as an anchor TRP that maximizes the reconstruction accuracy (e.g., compared to any other TRP in the set being used as an anchor TRP). In another example, the WTRU may select a TRP as an anchor TRP if it achieves a minimum required reconstruction accuracy.

[0265] For example, one factor may be feedback overhead. For example, the WTRU may select a TRP based on the available feedback overhead. For example, the WTRU may select a TRP that minimizes the required feedback overhead. In another example, the WTRU may select a TRP that maximizes the feedback accuracy for the configured feedback overhead.

[0266] For example, one factor may be prediction (in time, space, or frequency) of any of the above. For example, a WTRU may obtain a predicted value for any of the listed examples. The predicted value may be obtained from an AI / ML model. In an example, a WTRU may predict a future reconstruction error and may select a TRP as an anchor TRP that minimizes the predicted future reconstruction error. In another example, a WTRU may predict a future measurement or a measurement in a second frequency band or a measurement for a second TRP (e.g., based on a current measurement, or a measurement in a first band, or a measurement for a first TRP) and the WTRU may select the TRP as an anchor TRP based on the predicted measurement.

[0267] A WTRU may determine an anchor RS (e.g., CSI-RS) using any of the above methods, where determining anchor TRP may be considered equivalent to determining anchor RS.

[0268] A WTRU may be configured with one or more co-phasing representation types. The cophasing representation type may include one or more of: (0,360) or (0,2TT) ; (cos (p , sign(sin 0)); (sin <p , sign(cos 0)); and / or, (cos <p , sin 0). Where (p is the co-phase value between the measured channels associated with two TRPs.

[0269] A WTRU may determine a co-phasing representation type to use for one or more feedback reports. The determination of a co-phase representation type may be based on one or more factors described herein.

[0270] For example, one factor may be determined or selected anchor TRP / cell.

[0271] For example, one factor may be RS configuration associated with one or more TRPs.

[0272] For example, one factor may be timing. For example, a WTRU determines the co-phasing representation type based on the timing of the determination or the timing of the feedback report.

[0273] For example, one factor may be WTRU mobility parameter. For example, the WTRU may select a co-phase representation type based on at least one of: its location, its speed, its direction of movement.

[0274] For example, one factor may be measurements. For example, the WTRU may select a cophase representation type based on channel measurements such as RSRP, CSI (e.g., Rl, CQI, PMI, LI, CRI), RSRQ, SINR, RSSI, Channel Occupancy, AoA, AoD, Doppler shift, Doppler spread, Delay spread, average delay.

[0275] For example, one factor may be previous feedback. For example, a selected or determined co-phase representation type may be valid for multiple consecutive feedback reports.

[0276] For example, one factor may be associated transmission. For example, a WTRU may report feedback for a transmission of a type or associated with a set of transmission parameters (e.g., reliability, latency, priority, etc.). Based on the associated transmission type or set of transmission parameters, the WTRU may determine or select a co-phase representation type.

[0277] For example, one factor may be reconstruction accuracy. For example, a WTRU may determine a reconstruction accuracy associated with one or more co-phase representation type. The WTRU may select a co-phase representation type such that the reconstruction accuracy is maximized. In another example, the WTRU may select a co-phase representation type such that a possibly configurable threshold accuracy level is achieved.

[0278] For example, one factor may be feedback overhead. For example, a WTRU may determine a feedback overhead associated with one or more co-phase representation types. The WTRU may select a co-phase representation type that minimizes the feedback overhead. In another example, the WTRU may select a co-phase representation type such that a possibly configurable threshold feedback overhead is achieved. The feedback overhead may be the overhead of the co-phase information alone or the total feedback overhead of the entire feedback report (e.g., including for example the co-phase information and additional joint or separate channel information of one or more TRPs).

[0279] For example, one factor may be priority of a co-phase representation type. For example, a WTRU may select a co-phase representation type of the highest priority that achieves one or more criteria (e.g ., overhead threshold or accuracy threshold).

[0280] For example, one factor may be prediction (e.g., in time, space, frequency) of any of the above. For example, a WTRU may select a co-phase representation type that is predicted to achieve one or more criteria in a second time instance, or in a second BW or for a second beam, based on measurements in a first time instance, or in a first BW or for a first beam.

[0281] A WTRU may indicate the determined / selected anchor TRP, or the determined / selected cophasing representation type in a feedback report (e.g., a dedicated feedback report to indicate the selected anchor TRP or co-phase representation type, or a feedback report within which the selected anchor TRP or co-phase representation type is used to generate a feedback value).

[0282] The WTRU may compute the co-phasing information between the channels of two or more TRPs based on channel measurements for the two or more TRPs (e.g., measurements performed on RSs associated with the two or more TRPs), the determined / selected anchor TRP, and / or the determined / selected co-phase representation type.

[0283] The WTRU may compress the feedback report (e.g., where the feedback report may include one or more of: co-phase information for one or more TRPs, channel measurements for one or more TRPs, and / or differential channel information for one or more TRPs) and may determine the compression rate based on the selected co-phase representation type or payload thereof. Compression may be performed using an encoder (e.g., using an AI / ML autoencoder structure), where the parameters of the AI / ML model or the model itself, may be determined based on one or more of: the selected anchor TRP, channel measurements, and / or the selected co-phase representation type.

[0284] In an example, a WTRU may be configured with AI / ML based co-phasing compression, receives CSI-RS and measures the co-phasing, determines co-phasing representation for AI / ML- based compression, determines reference CSI-RS, feeds back the compressed co-phasing, type of phase representation and reference CSI-RS.

[0285] The WTRU may receive configuration to perform AI / ML-based co-phasing compression, where the configuration may include: phase representation type; anchor (reference) TRP for cophasing computation (e.g., the WTRU may be configured to determine the anchor (reference) TRP); threshold on reconstruction accuracy for the co-phasing information; and / or, threshold on feedback overhead for co-phasing information. For the co-phasing representation type, these may include one or more of: (0,360) or (0,2TT) ; (cos 0 , sign(sin 0)) ; (sin 0 , sign(cos 0)) ; and / or,(cos 0 , sin 0) (e.g., where 0 is the co-phase value between the measured channels associated with two TRPs).

[0286] The WTRU may receive an indication on the anchor (reference) TRP for co-phasing computation. In some instances, if the WTRU is indicated to determine the anchor TRP, then the WTRU may determine an anchor TRP (e.g., CSI-RS) as a function of the measured co-phasing. For example, the WTRU may select the CSI-RS with lowest average phase difference to other CSI-RS, as the reference.

[0287] The WTRU may receive indication on the type of phase representation to be used for compression. In some instances, if the WTRU is indicated to determine the phase representation type, then the WTRU may determine phase representation type as a function of configured accuracy target and feedback overhead. For example, if the WTRU is configured with a threshold on feedback overhead, then WTRU may select (cos cp , sign(sin 0)) if the overhead with (cos cp , sin 0) exceeds the feedback overhead threshold. As another example, if the WTRU is configured with a threshold on reconstruction accuracy, then the WTRU may select (cos cp , sin cp) if the accuracy with (cos cp , sign(sin 0)) is below the threshold on reconstruction accuracy. The WTRU may use a proxy (e.g., generic) WTRU-side decoder to measure the reconstruction accuracy.

[0288] The WTRU may compute the co-phasing information based on the phase representation and anchor TRP.

[0289] The WTRU may compress the co-phasing information using the AE encoder for co-phasing.

[0290] The WTRU may feedback (e.g., send one or more messages regarding) the compressed co-phasing, the determined phase representation type, and / or the determined reference TRP.

[0291] FIG. 8 illustrates an example process according to one or more embodiments disclosed herein. As illustrated, there may be a method for use in a wireless transmit receive unit (WTRU). At 802, the WTRU may receive configuration information regarding linear coded channel state information (CSI) compression for multiple transmission receive points (TRPs). At 804, the WTRU may receive a CSI-reference signal (RS) from each of a plurality of TRPs. At 806, the WTRU may perform measurements using the CSI-RS on one or more associated channels for each of the plurality of TRPs. At 805, the WTRU may determine a linear coding matrix based on the configuration information and the measurements of one or more associated channels for each of the plurality of TRPs. At 810, the WTRU may compute a set of linear combinations of channel matrices according to the determined linear coding matrix and the measurements of the one or more associated channels. At 812, the WTRU may compress the set of linear combinations of channel matrices. At 814, the WTRU may send the compressed set of linear combinations of channel matrices and information associated with the determined linear codingmatrix. In some instances, the configuration information may include one or more of: a set of linear coding matrices, the plurality of TRPs (M), priorities of TRP-to-WTRU links, and / or a number of additional CSI reports. In some instances, linear coding matrix may be determined further based on a number of additional CSI reports. In some instances, the additional number of CSI reports may be determined based on historical error rate, mismatch rate, or allowed feedback overhead. In some instances, the linear coding matrix may be determined further based on estimated mismatch metric or a statistical distribution of channel matrices. In some instances, the information associated with the determined linear coding matrix may include the determined linear coding matrix or an index to identify the determined linear coding matrix. In some instances, the information associated with the determined linear coding matrix may include a determined number of additional CSI reports. In some instances, the compressing the set of linear combinations may be performed using multiple encoders for each combination in order to generate a plurality of CSI reports, or using a single encoder for all combinations to generate a single CSI report.

[0292] As described herein, a higher layer may refer to one or more layers in a protocol stack, or a specific sublayer within the protocol stack. The protocol stack may comprise of one or more layers in a WTRU or a network node (e.g., eNB, gNB, other functional entity, etc.), where each layer may have one or more sublayers. Each layer / sublayer may be responsible for one or more functions. Each layer / sublayer may communicate with one or more of the other layers / sublayers, directly or indirectly. In some cases, these layers may be numbered, such as Layer 1 , Layer 2, and Layer 3. For example, Layer 3 may comprise of one or more of the following: Non-Access Stratum (NAS), Internet Protocol (IP), and / or Radio Resource Control (RRC). For example, Layer 2 may comprise of one or more of the following: Packet Data Convergence Control (PDCP), Radio Link Control (RLC), and / or Medium Access Control (MAC). For example, Layer 3 may comprise of physical (PHY) layer type operations. The greater the number of the layer, the higher it is relative to other layers (e.g., Layer 3 is higher than Layer 1). In some cases, the aforementioned examples may be called layers / sublayers themselves irrespective of layer number, and may be referred to as a higher layer as described herein. For example, from highest to lowest, a higher layer may refer to one or more of the following layers / sublayers: a NAS layer, a RRC layer, a PDCP layer, a RLC layer, a MAC layer, and / or a PHY layer. Any reference herein to a higher layer in conjunction with a process, device, or system will refer to a layer that is higher than the layer of the process, device, or system. In some cases, reference to a higher layer herein may refer to a function or operation performed by one or more layers described herein. In some cases, reference to a high layer herein may refer to information that is sent or received by one or more layers described herein. In some cases, reference to a higher layer herein may refer to a configuration that is sent and / or received by one or more layers described herein.

[0293] Although features and elements are described above in particular combinations (e.g., embodiments, methods, examples, etc.), 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. For example, as disclosed herein there may be a method described in association with a figure for illustrative purposes, and one of ordinary skill in the art will appreciate that one or more features or elements from this method may be used alone or in combination with one or more features from another method described elsewhere. A symbol 7’ (e.g., forward slash) may be used herein to represent ‘and / or’, where for example, A / B’ may imply ‘A and / or B’. As used herein, ‘a’ and ‘an’ and similar phrases are to be interpreted as ‘one or more’ and ‘at least one’. Similarly, any term which ends with the suffix ‘(s)’ is to be interpreted as ‘one or more’ and ‘at least one’. The term ‘may’ is to be interpreted as ‘may, for example’ or indicate that something "does happen" or "can happen". In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over 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.

[0294] As disclosed herein, ‘a’ and ‘an’ and similar phrases are to be interpreted as ‘one or more’ and ‘at least one’. Similarly, any term which ends with the suffix ‘(s)’ is to be interpreted as ‘one or more’ and ‘at least one’. The term ‘may’ is to be interpreted as ‘may, for example’. A symbol 7’ (e.g., forward slash) as used herein, unless otherwise indicated, represents ‘and / or’, where for example, ‘A / B’ may imply ‘A and / or B’.

Claims

CLAIMSWhat is Claimed:1 . A method for use in a wireless transmit receive unit (WTRU), the method comprising: receiving configuration information regarding linear coded channel state information (CSI) compression for multiple transmission receive points (TRPs); receiving a CSI-reference signal (RS) from each of a plurality of TRPs; performing measurements using the CSI-RS on one or more associated channels for each of the plurality of TRPs; determining a linear coding matrix based on the configuration information and the measurements of one or more associated channels for each of the plurality of TRPs; computing a set of linear combinations of channel matrices according to the determined linear coding matrix and the measurements of the one or more associated channels; compressing the set of linear combinations of channel matrices; and sending the compressed set of linear combinations of channel matrices and information associated with the determined linear coding matrix.

2. The method of claim 1 , wherein the configuration information includes one or more of: a set of linear coding matrices, the plurality of TRPs (M), priorities of TRP-to-WTRU links, a number of additional CSI reports.

3. The method of claim 1 , wherein the linear coding matrix is determined further based on a number of additional CSI reports.

4. The method of claim 3, wherein the additional number of CSI reports are determined based on historical error rate, mismatch rate, or allowed feedback overhead.

5. The method of claim 1 , wherein the linear coding matrix is determined further based on estimated mismatch metric or a statistical distribution of channel matrices.

6. The method of claim 1 , wherein the information associated with the determined linear coding matrix include the determined linear coding matrix or an index to identify the determined linear coding matrix.

7. The method of claim 1 , wherein the information associated with the determined linear coding matrix include a determined number of additional CSI reports.

8. The method of claim 1 , wherein compressing the set of linear combinations is performed using multiple encoders for each combination in order to generate a plurality of CSI reports, or using a single encoder for all combinations to generate a single CSI report.

9. A wireless transmit receive unit (WTRU), the WTRU comprising: a processor operatively coupled to transceiver, the processor and transceiver configured to receive configuration information regarding linear coded channel state information (CSI) compression for multiple transmission receive points (TRPs); the processor and transceiver configured to receive a CSI-reference signal (RS) from each of a plurality of TRPs; the processor and transceiver configured to perform measurements using the CSI-RS on one or more associated channels for each of the plurality of TRPs; the processor and transceiver configured to determine a linear coding matrix based on the configuration information and the measurements of one or more associated channels for each of the plurality of TRPs; the processor and transceiver configured to compute a set of linear combinations of channel matrices according to the determined linear coding matrix and the measurements of the one or more associated channels; the processor and transceiver configured to compress the set of linear combinations of channel matrices; and the processor and transceiver configured to send the compressed set of linear combinations of channel matrices and information associated with the determined linear coding matrix.

10. The WTRU of claim 9, wherein the configuration information includes one or more of: a set of linear coding matrices, the plurality of TRPs (M), priorities of TRP-to-WTRU links, a number of additional CSI reports.11 . The WTRU of claim 9, wherein the linear coding matrix is determined further based on a number of additional CSI reports.

12. The WTRU of claim 11 , wherein the additional number of CSI reports are determined based on historical error rate, mismatch rate, or allowed feedback overhead.

13. The WTRU of claim 9, wherein the linear coding matrix is determined further based on estimated mismatch metric or a statistical distribution of channel matrices.

14. The WTRU of claim 9, wherein the information associated with the determined linear coding matrix include the determined linear coding matrix or an index to identify the determined linear coding matrix.

15. The WTRU of claim 9, wherein the information associated with the determined linear coding matrix include a determined number of additional CSI reports.

16. The WTRU of claim 9, wherein compressing the set of linear combinations is performed using multiple encoders for each combination in order to generate a plurality of CSI reports, or using a single encoder for all combinations to generate a single CSI report.

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