WO2023084422A1 - Methods and systems for pmi prediction with type ii csi - Google Patents

Abstract

A method performed by a network node is provided. The method comprises receiving an indication of one or more channel state information reference signal (CSI-RS) ports selected by UE; obtaining Doppler parameters for each selected CSI-RS port; and predicting, based on the obtained Doppler parameters for each selected CSI-RS port, channel state information (CSI) at a future time step for a channel associated with the selected one or more CSI-RS ports.

Description

METHODS AND SYSTEMS FOR PMI PREDICTION WITH TYPE II CSI

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/277,591 and U.S. Provisional Patent Application No. 63/277,544, both filed on November 9, 2021. The contents of both applications are hereby incorporated by reference in their entirety for all purposes.

FIELD

[0002] This present disclosure relates to Channel State Information (CSI) and Precoder Matrix Indicator (PMI) prediction in a wireless communication system.

BACKGROUND

[0003] Multi-antenna techniques can significantly increase the data rates and reliability of a wireless communication system. The performance can be improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a multiple -input multiple-output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO. If the same block of spectrum is shared among multiple users, the technology is referred to as MU-MIMO.

[0004] The New Radio (NR) standard is currently evolving with enhanced MIMO support. A component in NR is the support of MIMO antenna deployments and MIMO related techniques including, for instance, spatial multiplexing. The spatial multiplexing mode is aimed for high data rates in favorable channel conditions. When a user equipment (UE) moves with high speed, channel conditions may vary rapidly in time. As a result, the CSI report from the UE may be somewhat outdated when it reaches the network node since it takes time for the UE to compute and report the CSI. If the network node uses this CSI for downlink precoding, the performance may be degraded, compared to the stationary-UE scenario. Thus, there is a need to improve CSI.

SUMMARY

[0005] Various computer-implemented systems, methods, and articles of manufacture for CSI reporting are described herein.

[0006] In one embodiment, a method performed by a network node is provided. The method comprises receiving an indication of one or more channel state information reference signal (CSI- RS) ports selected by UE; obtaining Doppler parameters for each selected CSI-RS port; and predicting, based on the obtained Doppler parameters for each selected CSI-RS port, channel state information (CSI) at a future time step for a channel associated with the selected one or more CSI- RS ports. [0007] In one embodiment, a method performed by a network node is provided. The method comprises sending a configuration of one or more channel state information reference signal (CSI- RS) resources to a user equipment (UE); receiving, from the UE, a CSI report. The CSI report comprises an indication of a set of frequency domain basis vectors, an indication of a plurality of sets of combination coefficients per layer at one or more time steps for combining one or more CSI-RS ports and the set of frequency domain basis vectors, an indication of the one or more CSI- RS ports selected by the UE, and an indication of Doppler parameters for each selected CSI-RS port. The one or more time steps for which the plurality of sets of combination coefficients are included in the CSI report are selected based on prioritization rules of communication resources. The method further comprises predicting, based on the obtained Doppler parameters for each selected CSI-RS port and the CSI report, channel state information for a channel associated with the one or more CSI-RS ports at a future time step.

[0008] In one embodiment, a network node, comprising processing circuitry is configured to perform the methods above.

[0009] In one embodiment, a method preformed by a UE is provided. The method comprises receiving a configuration of one or more CSI reference signal (CSI-RS) resources for channel measurements; performing the channel measurements on the one or more CSI-RS resources according to the received configuration; determining a set of frequency domain basis vectors and a plurality of sets of combination coefficients per layer at multiple time steps for combining the CSI-RS ports and the set of frequency domain basis vectors; and sending a CSI report to the network node. The CSI report comprises the indication of the set of frequency domain basis vectors, the indication of the plurality of sets of combination coefficients per layer at the multiple time steps for combining the CSI-RS ports and the set of frequency domain basis vectors, and an indication of one or more selected (CSI-RS) ports. The multiple time steps for which the plurality of sets of combination coefficients are included in the CSI report are selected based on prioritization rules of communication resources.

[0010] In one embodiment, a UE, comprising processing circuitry is configured to perform the method above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of the various described embodiments, reference should be made to the Detailed Description below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures.

[0012] Figure 1 illustrates an exemplary wireless network in accordance with some embodiments. [0013] Figure 2 illustrates an exemplary user equipment in accordance with some embodiments.

[0014] Figure 3 illustrates an exemplary virtualization environment in accordance with some embodiments.

[0015] Figure 4 illustrates an exemplary telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments.

[0016] Figure 5 illustrates an exemplary host computer communicating via a base station with a user equipment over a partially wireless connection in accordance with some embodiments.

[0017] Figure 6 illustrates an exemplary method implemented in a communication system including a host computer, a base station, and a user equipment in accordance with some embodiments.

[0018] Figure 7 is a block diagram illustrating a spatial multiplexing operation in accordance with some embodiments.

[0019]

[0020] Figure 8 illustrates an example procedure for a reciprocity based FDD transmission scheme, according to some embodiments.

[0021] Figure 9 illustrates an example of CSI-RS precoding and Type II PMI calculation based on angle-delay reciprocity, according to some embodiments.

[0022] Figure 10 is a flowchart illustrating a method performed by a network node and user equipment for CSI reporting and predicting, according to some embodiments.

[0023] Figure 11A is a diagram illustrating an example of CSI-RS transmission in multiple time steps for CSI reporting.

[0024] Figure 11B is a diagram illustrating an example of a phase slope derived based on multiple time steps for a coefficient of W2(t).

[0025] Figure 12 is a flowchart illustrating a method performed by a network node for CSI predicting, according to some embodiments.

[0026] Figure 13 is a flowchart illustrating a method performed by a user equipment for CSI reporting, according to some embodiments.

DETAILED DESCRIPTION

[0027] Certain aspects of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. This concept may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the concept to those skilled in the art.

[0028] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise:

[0029] The phrase “in one embodiment” as used herein does not necessarily refer to the same embodiment, though it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0030] As used herein, the term “or” is an inclusive “or” operator and is equivalent to the term “and/or,” unless the context clearly dictates otherwise.

[0031] The term “based on” is not exclusive and allows for being based on additional factors not described unless the context clearly dictates otherwise.

[0032] In addition, throughout the specification, the meaning of “a”, “an”, and “the” includes plural references, and the meaning of “in” includes “in” and “on”.

[0033] Although some of the various embodiments presented herein constitute a single combination of inventive elements, it should be appreciated that the inventive subject matter is considered to include all possible combinations of the disclosed elements. As such, if one embodiment comprises elements A, B, and C, and another embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly discussed herein. Further, the transitional term “comprising” means to have as parts or members, or to be those parts or members. As used herein, the transitional term “comprising” is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.

[0034] In various embodiments, the devices, instruments, systems, and methods described herein may be used to predict the CSI based on estimation of Doppler parameters. In particular, a network node can use the time domain channel state information (e.g., Doppler shift, spread, and/or other Doppler parameters) associated with each beam angle and time delay cluster together with the associated CSI report from the UE to predict CSI at a future time step for a channel comprising multiple clusters (the channel is also referred to as a composite channel). A cluster is associated with propagation paths that show similar beam angles and time delays.

[0035] Based on various embodiments, a network node can receive an indication of one or more CSI reference signal (CSI-RS) ports selected by a UE; obtain Doppler parameters for each selected CSI-RS port; and predict, based on the obtained Doppler parameters for each selected CSI-RS port, CSI at a future time step for a channel associated with the selected one or more CSI- RS ports. Various embodiments thus provide more accurate CSI for time -varying channels. This can improve precoding performance and provide higher throughput and capacity. Further, the solutions described herein may not require any standard changes. Moreover, embodiments herein mitigate or reduce the problem where the CSI report from a medium-to-high mobility UE is outdated when estimation and computation for the CSI report are performed by the UE. As a result, the performance of the network communication can be improved, or the degradation of the performance can be prevented or reduced.

[0036] It is noted that description herein is not intended as an extensive overview, and as such, concepts may be simplified in the interests of clarity and brevity. Any process or method or corresponding steps of any process or method described in this application may be performed in any order and may omit any of the steps in the process. Processes or methods may also be combined with other processes or steps of other processes, in part or in whole. Parts of processes or methods, or corresponding steps may be combined with other parts of processes or methods, or corresponding steps.

[0037] Although the subject matter described herein may be implemented in any appropriate type of system using any suitable components, the embodiments disclosed herein are described in relation to a wireless network, such as the example wireless network illustrated in Figure 1.

[0038] Figure 1 shows an example of a communication system 100 in accordance with some embodiments.

[0039] In the example, the communication system 100 includes a telecommunication network

102 that includes an access network 104, such as a radio access network (RAN), and a core network 106, which includes one or more core network nodes 108. The access network 104 includes one or more access network nodes, such as network nodes 110a and 110b (one or more of which may be generally referred to as network nodes 110), or any other similar 3^rd Generation Partnership Project (3GPP) access node or non-3GPP access point. The network nodes 110 facilitate direct or indirect connection of UE, such as by connecting UEs 112a, 112b, 112c, and 112d (one or more of which may be generally referred to as UEs 112) to the core network 106 over one or more wireless connections.

[0040] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

[0041] The UEs 112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 110 and other communication devices. Similarly, the network nodes 110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 112 and/or with other network nodes or equipment in the telecommunication network 102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 102.

[0042] In the depicted example, the core network 106 connects the network nodes 110 to one or more hosts, such as host 116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 106 includes one more core network nodes (e.g., core network node 108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

[0043] The host 116 may be under the ownership or control of a service provider other than an operator or provider of the access network 104 and/or the telecommunication network 102, and may be operated by the service provider or on behalf of the service provider. The host 116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0044] As a whole, the communication system 100 of Figure 1 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0045] In some examples, the telecommunication network 102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 102. For example, the telecommunications network 102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)ZMassive loT services to yet further UEs.

[0046] In some examples, the UEs 112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) NR - Dual Connectivity (EN-DC).

[0047] In the example, the hub 114 communicates with the access network 104 to facilitate indirect communication between one or more UEs (e.g., UE 112c and/or 112d) and network nodes (e.g., network node 110b).

[0048] The hub 114 may have a constant/persistent or intermittent connection to the network node 110b. The hub 114 may also allow for a different communication scheme and/or schedule between the hub 114 and UEs (e.g., UE 112c and/or 112d), and between the hub 114 and the core network 106. In other examples, the hub 114 is connected to the core network 106 and/or one or more UEs via a wired connection.

[0049] Figure 2 shows a UE 200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3GPP, including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.

[0050] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to- everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller).

[0051] The UE 200 includes processing circuitry 202 that is operatively coupled via a bus 204 to an input/output interface 206, a power source 208, a memory 210, a communication interface 212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 2. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0052] The processing circuitry 202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 210. The processing circuitry 202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field- programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 202 may include multiple central processing units (CPUs). Also, the processing circuitry 202 is configured to perform any steps of method 1300 of Figure 13.

[0053] In the example, the input/output interface 206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. [0054] In some embodiments, the power source 208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 208 may further include power circuitry for delivering power from the power source 208 itself, and/or an external power source, to the various parts of the UE 200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 208 to make the power suitable for the respective components of the UE 200 to which power is supplied.

[0055] The memory 210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically EPROM(EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 210 includes one or more application programs 214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 216. The memory 210 may store, for use by the UE 200, any of a variety of various operating systems or combinations of operating systems. [0056] The memory 210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory 210 may allow the UE 200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 210, which may be or comprise a device-readable storage medium.

[0057] The processing circuitry 202 may be configured to communicate with an access network or other network using the communication interface 212. The communication interface 212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 222. The communication interface 212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 218 and/or a receiver 220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 218 and receiver 220 may be coupled to one or more antennas (e.g., antenna 222) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0058] In the illustrated embodiment, communication functions of the communication interface 212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE,NR, UMTS, WiMax, Ethernet, transmission control protocol/intemet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0059] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE.

[0060] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection.

[0061] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and/or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE 200 shown in Figure 2.

[0062] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

[0063] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone.

[0064] Figure 3 shows a network node 300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs (NBs), evolved NBs (eNBs) and NRNBs (gNBs)).

[0065] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0066] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

[0067] The network node 300 includes a processing circuitry 302, a memory 304, a communication interface 306, and a power source 308. The network node 300 may be composed of multiple physically separate components (e.g., a NB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NBs. In such a scenario, each unique NB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 304 for different RATs) and some components may be reused (e.g., a same antenna 310 may be shared by different RATs). The network node 300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 300.

[0068] The processing circuitry 302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 300 components, such as the memory 304, to provide network node 300 functionality.

[0069] In some embodiments, the processing circuitry 302 includes a system on a chip (SOC). In some embodiments, the processing circuitry 302 includes one or more of radio frequency (RF) transceiver circuitry 312 and baseband processing circuitry 314. In some embodiments, the RF transceiver circuitry 312 and the baseband processing circuitry 314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 312 and baseband processing circuitry 314 may be on the same chip or set of chips, boards, or units. For example, the processing circuitry 302 is configured to perform method 1200 of Figure 12.

[0070] The memory 304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 302. The memory 304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 302 and utilized by the network node 300. The memory 304 may be used to store any calculations made by the processing circuitry 302 and/or any data received via the communication interface 306. In some embodiments, the processing circuitry 302 and memory 304 is integrated.

[0071] The communication interface 306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 306 comprises port(s)/terminal(s) 316 to send and receive data, for example to and from a network over a wired connection. The communication interface 306 also includes radio front-end circuitry 318 that may be coupled to, or in certain embodiments a part of, the antenna 310. Radio front-end circuitry 318 comprises filters 320 and amplifiers 322. The radio front-end circuitry 318 may be connected to an antenna 310 and processing circuitry 302. The radio front-end circuitry may be configured to condition signals communicated between antenna 310 and processing circuitry 302. The radio front-end circuitry 318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 320 and/or amplifiers 322. The radio signal may then be transmitted via the antenna 310. Similarly, when receiving data, the antenna 310 may collect radio signals which are then converted into digital data by the radio front-end circuitry 318. The digital data may be passed to the processing circuitry 302. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

[0072] In certain alternative embodiments, the network node 300 does not include separate radio front-end circuitry 318, instead, the processing circuitry 302 includes radio front-end circuitry and is connected to the antenna 310. Similarly, in some embodiments, all or some of the RF transceiver circuitry 312 is part of the communication interface 306. In still other embodiments, the communication interface 306 includes one or more ports or terminals 316, the radio front-end circuitry 318, and the RF transceiver circuitry 312, as part of a radio unit (not shown), and the communication interface 306 communicates with the baseband processing circuitry 314, which is part of a digital unit (not shown).

[0073] The antenna 310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 310 may be coupled to the radio front-end circuitry 318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 310 is separate from the network node 300 and connectable to the network node 300 through an interface or port.

[0074] The antenna 310, communication interface 306, and/or the processing circuitry 302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 310, the communication interface 306, and/or the processing circuitry 302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

[0075] The power source 308 provides power to the various components of network node 300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 300 with power for performing the functionality described herein. For example, the network node 300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 308. As a further example, the power source 308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0076] Embodiments of the network node 300 may include additional components beyond those shown in Figure 3 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein.

[0077] Figure 4 is a block diagram of a host 400, which may be an embodiment of the host 116 of Figure 1, in accordance with various aspects described herein. As used herein, the host 400 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 400 may provide one or more services to one or more UEs.

[0078] The host 400 includes processing circuitry 402 that is operatively coupled via a bus 404 to an input/output interface 406, a network interface 408, a power source 410, and a memory 412. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 2 and 3, such that the descriptions thereof are generally applicable to the corresponding components of host 400.

[0079] The memory 412 may include one or more computer programs including one or more host application programs 414 and data 416, which may include user data, e.g., data generated by a UE for the host 400 or data generated by the host 400 for a UE. Embodiments of the host 400 may utilize only a subset or all of the components shown. The host application programs 414 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs 414 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 400 may select and/or indicate a different host for over-the-top services for a UE. The host application programs 414 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[0080] Figure 5 is a block diagram illustrating a virtualization environment 500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized.

[0081] Applications 502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

[0082] Hardware 504 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 508a and 508b (one or more of which may be generally referred to as VMs 508), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer 506 may present a virtual operating platform that appears like networking hardware to the VMs 508.

[0083] The VMs 508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 506. Different embodiments of the instance of a virtual appliance 502 may be implemented on one or more of VMs 508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0084] In the context of NFV, a VM 508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non- virtualized machine. Each of the VMs 508, and that part of hardware 504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 508 on top of the hardware 504 and corresponds to the application 502.

[0085] Hardware 504 may be implemented in a standalone network node with generic or specific components. Hardware 504 may implement some functions via virtualization. Alternatively, hardware 504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 510, which, among others, oversees lifecycle management of applications 502. In some embodiments, hardware 504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 512 which may alternatively be used for communication between hardware nodes and radio units.

[0086] Figure 6 shows a communication diagram of a host 602 communicating via a network node 604 with a UE 606 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE 112a of Figure 1 and/or UE 200 of Figure 2), network node (such as network node 110a of Figure 1 and/or network node 300 of Figure 3), and host (such as host 116 of Figure 1 and/or host 400 of Figure 4) discussed in the preceding paragraphs will now be described with reference to Figure 6.

[0087] Like host 400, embodiments of host 602 include hardware, such as a communication interface, processing circuitry, and memory. The host 602 also includes software, which is stored in or accessible by the host 602 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 606 connecting via an over-the-top (OTT) connection 650 extending between the UE 606 and host 602. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 650.

[0088] The network node 604 includes hardware enabling it to communicate with the host 602 and UE 606. The connection 660 may be direct or pass through a core network (like core network 106 of Figure 1) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

[0089] The UE 606 includes hardware and software, which is stored in or accessible by UE 606 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE 606 with the support of the host 602. In the host 602, an executing host application may communicate with the executing client application via the OTT connection 650 terminating at the UE 606 and host 602. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 650 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 650. [0090] The OTT connection 650 may extend via a connection 660 between the host 602 and the network node 604 and via a wireless connection 670 between the network node 604 and the UE 606 to provide the connection between the host 602 and the UE 606. The connection 660 and wireless connection 670, over which the OTT connection 650 may be provided, have been drawn abstractly to illustrate the communication between the host 602 and the UE 606 via the network node 604, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

[0091] As an example of transmitting data via the OTT connection 650, in step 608, the host 602 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 606. In other embodiments, the user data is associated with a UE 606 that shares data with the host 602 without explicit human interaction. In step 610, the host 602 initiates a transmission carrying the user data towards the UE 606. The host 602 may initiate the transmission responsive to a request transmitted by the UE 606. The request may be caused by human interaction with the UE 606 or by operation of the client application executing on the UE 606. The transmission may pass via the network node 604, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 612, the network node 604 transmits to the UE 606 the user data that was carried in the transmission that the host 602 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 614, the UE 606 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 606 associated with the host application executed by the host 602.

[0092] In some examples, the UE 606 executes a client application which provides user data to the host 602. The user data may be provided in reaction or response to the data received from the host 602. Accordingly, in step 616, the UE 606 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE 606. Regardless of the specific manner in which the user data was provided, the UE 606 initiates, in step 618, transmission of the user data towards the host 602 via the network node 604. In step 620, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 604 receives user data from the UE 606 and initiates transmission of the received user data towards the host 602. In step 622, the host 602 receives the user data carried in the transmission initiated by the UE 606.

[0093] One or more of the various embodiments improve the performance of OTT services provided to the UE 606 using the OTT connection 650, in which the wireless connection 670 forms the last segment. More precisely, the teachings of these embodiments may improve the Type II CSI reporting and enable the network node to predict CSI at a future time step. The various embodiments thus may provide more accurate CSI for time-varying channels. This can improve precoding performance and thereby provide higher throughput and capacity.

[0094] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 650 between the host 602 and UE 606, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 602 and/or UE 606. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 650 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 650 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node 604. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 602. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 650 while monitoring propagation times, errors, etc. In this disclosure, the UEs and network nodes are the same or substantially the same across all figures, even if they have different reference numbers.

[0095] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. [0096] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device -readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

[0097] As described above, a core component in NR is the support of MIMO antenna deployments and MIMO related techniques like for instance spatial multiplexing. The spatial multiplexing mode is aimed for high data rates in favorable channel conditions. An illustration of the spatial multiplexing operation is provided in Figure 7. Figure 7 is a block diagram for a spatial multiplexing operation according to some embodiments. A codebook in the context of CSI-RS is a set of precoders in a precoding matrix. In some embodiments, a codebook matrix transforms the data bit (PDSCH) to another set of data that maps to each antenna port.

[0098] As shown in Figure 7, for precoding, the information carrying symbol vector .s' 702 is multiplied by an NT X r precoder matrix IV 704. The precoder matrix W 704 serves to distribute the transmit energy in a subspace of the NT (corresponding to NT antenna ports 708) dimensional vector space. In some embodiments, the precoder matrix IF 704 is selected from a codebook of possible precoder matrices and indicated by means of a precoder matrix indicator (PMI), which specifies a unique precoder matrix in the codebook for a given number of symbol streams. The r symbols in the vector 5 702 each corresponds to a layer (e.g., transmission layers 706a-706r) and r is referred to as the transmission rank. In this way, spatial multiplexing can be achieved since multiple symbols can be transmitted simultaneously over the same time/frequency resource element (TFRE). The number of symbols r is typically adapted to suit the current channel properties. [0099] The new radio uses orthogonal frequency-division multiplexing (OFDM) techniques in the downlink (UL) and discrete Fourier Transform (DFT) precoded OFDM in the uplink (UL) for rank-1 transmission. Therefore, the received NR X 1 vector y_n for a certain TFRE on subcarrier n (or alternatively data TFRE number n) is modeled by formula [1] below.

Vn H_nWs_n + (?_n [1]

[0100] In formula [1] above, e_n denotes a noise/interference vector obtained as realizations of a random process, NR corresponds to the number of antenna ports at the receiver. The precoder matrix W 704 can be a wideband precoder, which is constant over frequency, or a frequency selective.

[0101] The precoder matrix W 704 is often chosen to match the characteristics of the NRXNT MIMO channel matrix H_n , resulting in so-called channel dependent precoding. This is also commonly referred to as closed-loop precoding and essentially strives for focusing the transmit energy into a subspace which is strong in the sense of conveying much of the transmitted energy to the UE.

[0102] In closed-loop precoding for the NR downlink, the UE transmits, based on channel measurements in the downlink, recommendations to the network node or radio base station (e.g., gNB) of a suitable precoder to use. For example, the network node configures the UE to provide feedback according to a CSI reporting configuration (e.g., CSI-ReportConfig) and may transmit CSI-RS and configures the UE to use measurements of CSI-RS to feedback recommended precoding matrices that the UE selects from a codebook. A single precoder that is supposed to cover a large bandwidth (wideband precoding) may be fed back. In some embodiments, it may also be beneficial to match the frequency variations of the channel and instead provide feedback as a frequency-selective precoding report (e.g., several precoders, one per sub-band). This is an example of the more general case of channel state information (CSI) feedback, which also encompasses feeding back information other than recommended precoders to assist the network node in subsequent transmissions to the UE. Such other information may include channel quality indicators (CQIs) and transmission rank indicator (RI). In NR, CSI feedback can be either wideband, where one CSI is reported for the entire channel bandwidth, or frequency-selective, where one CSI is reported for each sub-band, which is defined as a predetermined number of contiguous resource blocks ranging between 4-32 PRBS depending on the bandwidth part (BWP) size.

[0103] Provided with the CSI feedback from the UE, the network node determines the transmission parameters it intends to use to transmit to the UE, including the precoding matrix, transmission rank, and modulation and coding scheme (MCS). These transmission parameters may differ from the recommendations by the UE. The transmission rank, and thus the number of spatially multiplexed layers, is reflected in the number of columns of the precoder matrix IV 704. For efficient performance, a transmission rank that matches the channel properties is selected.

[0104] In a Frequency-division duplexing (FDD)-based reciprocity operation, the UL and DL transmissions are carried out on different frequencies. Thus, the propagation channels in UL and DL are not reciprocal as in the TDD case. However, some physical channel parameters such as angle of arrival/departure and the associated delays depend on only the spatial properties of the channel and are generally reciprocal between UL and DL. Such properties are exploited in NR Rel-17 enhanced Type II port selection codebook for DL channel state information (CSI) feedback, where the channel delay and angle information obtained in the UL is used to precode and delay- compensate CSI reference signals such that DL CSI can be fed back with much less overhead .

[0105] One example procedure for a reciprocity based FDD transmission scheme is illustrated in Figure 8. In Figure 8, UE 802 corresponds to any of the UEs described in the previous figures (e.g., UE 112A or 112B), and network node 801 corresponds to any network node described in the previous figures (e.g., network node 110A or 110B).

[0106] With reference to Figure 8, at step 1, UE 802 is configured with a sound reference signal (SRS) by the network node 801. UE 802 transmits the SRS in the UL to the network node 801. Network node 801 estimates the angles and associated delays of different multipath channel clusters, which are associated with different propagation paths.

[0107] At step 2, the network node 801 selects dominant clusters according to the estimated angle-delay power spectrum profile. Based on the estimated angle-delay power spectrum profile, a set of spatial-domain (SD) basis vectors (or beams) and a set of delays are computed by the network node 801 for CSI-RS precoding or beamforming. For each beam (or SD basis vector) and delay pair, a CSI-RS port is allocated. Network node 801 applies a precoder (which is the SD basis vector) and a delay pre -compensation to each of the CSI-RS ports in a configured CSI-RS resource or multiple CSI-RS resources to UE 802 such that all the CSI-RS reach the UE at the same time.

[0108] At step 3, network node 801 has configured UE 802 to measure the channel based on the received CSI-RS, and UE 802 measures the received CSI-RS ports and then determines a type II CSI including RI (rank indicator), PMI (precoding matrix indicator) for each layer, and CQI (channel quality indicator). The precoding matrix indicated by the PMI includes a set of UE selected CSI-RS ports out of the configured CSI-RS ports and one or more frequency domain (FD) basis vectors out of a full set of FD basis vectors, where each FD basis vector corresponds to a channel delay. Ideally, if the channel includes only a set of discrete propagation paths with well separated angles and delays, all the CSI-RS would be time aligned at the UE and there would be only a single FD basis vector that is needed. However, due to the limited number of CSI-RS ports and that the channel multipath may not be well separated, the CSI-RS received at the UE may not be able to be represent by a single delay or FD basis vector. Therefore, more than one FD basis vector may be needed. The precoding matrix further comprises the corresponding phase and amplitude for the selected CSI-RS ports (or beams) and the FD basis vectors. The phase and amplitude are quantized and sent back to network node 801 as part of a type II CSI report.

[0109] At step 4, network node 801 computes a DL precoding matrix per layer based on the UE reported beams or CSI-RS ports, FD basis vectors, and the corresponding amplitudes and phases, and applies the precoding matrix (or precode) to Physical Downlink Shared Channel (PDSCH) transmission. The transmission can be based on the fed-back precoding matrices directly (e.g., SU-MIMO transmission), or the transmission precoding matrix is obtained by considering CSI feedback from multiple co-scheduled UEs (MU-MIMO transmission) where the precoder could be derived based on the precoding matrices including the CSI reports from co-scheduled UEs (for example, a Zero-Forcing (ZF) precoder or a regularized ZF precoder). The final precoder is commonly scaled so that the transmit power per power amplifier is not overridden.

[0110] As described above, Figure 8 is a diagram illustrating a procedure of codebook-based transmission for FDD with delay and angle reciprocity between DL and UL. Such reciprocitybased transmission can potentially be utilized in a codebook-based DL transmission for FDD to, for example, reduce the feedback overhead in UL when the NR Rel-17 enhanced Type II portselection codebook is used. Another potential benefit is reduced complexity in the CSI calculation performed by UE 802. It is understood that As described above, 8 only illustrates one example of the procedure for FDD-based reciprocity operation, where each CSI-RS port contains a single SD basis and delay pair. In some embodiments, each CSI-RS port may contain multiple SD-FD basis pairs, and that UE 802 can compress the channel with more FD components besides the DC DFT component.

[0111] Based on the angle and delay reciprocity, network node 801 can determine a set of dominant clusters in the propagation channel by analyzing the angle -delay power spectrum of the UL channel. Then, network node 801 can utilize this information in a way such that each CSI-RS port is precoded towards a dominant cluster. A dominant cluster in a propagation channel corresponds to one or more strongest peaks in a power spectrum of the channel. The strongest peaks refer to the local maxima in the power spectrum. A cluster corresponds to a local maximum in the power spectrum. In addition to SD beamforming, each of the CSI-RS ports will also be precompensated in time such that all the precoded CSI-RS ports are aligned in the delay domain. As a result, frequency-selectivity of the channel is removed and UE 802 observes a frequency-flat channel, which requires very small number of FD basis vectors to compress. If all the beams can be perfectly aligned in time, UE 802 performs a wideband filtering to obtain all the channel information, based on which UE 802 can calculate the Rel-17 Type II PMI. Even if delay cannot be perfectly pre-compensated at network node 801, the frequency selectively seen at UE 802 can still be greatly reduced, so that UE 802 uses a much smaller number of FD basis vectors to compress the channel.

[0112] In summary, in NR Rel-17 type II port selection codebook, the precoding matrix for each layer can be expressed as W^l = W W₂ W , where is a CSI-RS port selection matrix of size N by 2L with each column containing one element of integer one and the rest of the elements of zeros, lV_f is a DFT matrix of size N3 by M, representing the selected FD basis vectors for layer I, and W_2:i is a 2L by M coefficient matrix with each of its element representing the coefficient for a corresponding pair of selected SD and FD basis vectors, N is the number of configured CSI- RS ports, L is the configured ports or beams to be selected, N3 is the number of PMI subbands, and M is the number of FD basis vectors to be selected. For ease of discussion, the layer index I may be dropped from the matrices in the following sections.

[0113] The above procedure is further explained by an example in Figure 9. Based on UL measurement, network node 801 may identify eight dominant clusters that exist in the original channel, tagged as A-G, which are distributed in four directions, with each direction containing one or more taps (i.e., discrete delays). In this example, eight CSI-RS ports are precoded at network node 801. Each CSI-RS port is precoded towards a dominant direction with pre-compensated delay for a given cluster. As one example, the delay compensation can be realized by applying a linear phase rotation across occupied subcarriers. As a result, in the beamformed channel, which is seen at UE 802, all the dominant clusters are aligned at the same delay (equivalent to a frequency flat channel). Therefore, UE 802 applies a wideband fdter. For example, UE1102 applies the DC component of a DFT matrix (i.e., IF - containing a single FD basis vector where all elements in the vector having the value of “one”) to compress the channel and preserve all the channel information. Based on the compressed channel, the UE 802 calculates l ₁ (spatial domain basis vectors for selected CSI-RS ports) and W₂ (complex coefficients for combining selected ports), which are the remaining part of the Type II port selection codebook.

[0114] Figure 9 described above illustrates only an example of CSI-RS precoding and Type II PMI calculation based on angle -delay reciprocity.

[0115] As described above, the UE may move from one place to another and may move in a low, medium, or high velocity. The relative motion between a transmitter and a receiver results in a Doppler shift which is the change in frequency of a wave in relation to an observer who is moving relative to the wave source. The Doppler spread, which is a measure of the spectral broadening caused by the time rate of change of the mobile radio channel, can also be defined as the range of frequencies over which the received Doppler spectrum is essentially non-zero.

[0116] Assuming that the bandwidth of the transmitted signal is very small compared to the carrier frequency f_c, a signal component making an angle of 9 with the direction of motion of the receiver results in a Doppler shift of f_D = f_c • • cos 9, where v denotes the relative speed of the receiver, and c denotes the speed of light in free space. The maximum possible Doppler shift, fo.max obtained for 9 = 0 and n . In case of a multi-path propagation, signal

components arriving at the receiver from different directions experience different Doppler shifts and the total received signal exhibits a frequency spread around the carrier frequency. The width of the spread around the carrier frequency is referred to as Doppler spread. The precise definition of Doppler spread may vary across literature and _Dimax is often used as an approximation for Doppler spread.

[0117] The Doppler characteristics of the received signal are captured using the Doppler power spectrum, which is related to the autocorrelation function in time of the time-varying channel through a Fourier transform. Therefore, availability of Doppler power spectrum or its properties allows modeling of the time-variations of a channel. Under the assumption of a propagation environment where a receiver is surrounded by infinite scatterers uniformly distributed in a circle, the autocorrelation function in time is a Bessel function of the first kind with /o,max ^as an argument. In this scenario, an estimate of the maximum Doppler shift alone enables approximating the autocorrelation in time.

[0118] The term “Doppler information” or “Doppler parameter(s)” described herein refers to one or many of, e.g., Doppler shift, Doppler spread, and Doppler spectrum. Doppler information or parameter(s) can be used to describe the time domain channel characteristics.

[0119] As discussed above, when a UE moves with high speed, the channel will vary rapidly in time. Thus, the CSI report from the UE will be somewhat outdated when it reaches a network node since it takes time for the UE to compute and report the CSI. If the network node uses this CSI report for downlink precoding, the performance may be degraded, compared to the stationary- UE scenario.

[0120] One way to mitigate this problem and to reduce the impact of such rapid channel variations is to configure for faster CSI reporting (e.g., more frequent CSI reportings and measurements). A challenge associated with this approach is that it incurs a large signaling and reporting overhead. Furthermore, there is still a limitation in the minimum time needed for the UE to compute the CSI report. Hence, with the current CSI framework in NR, it is difficult to obtain accurate CSI for medium-to-high-speed UEs with a reasonable amount of overhead.

[0121] A potential solution to this problem associated with UEs having medium -to-high speed mobilities may be based on including Doppler parameters (e.g., information about the time variations of the channel and/or interference) in the CSI report from the UE. The Doppler parameters can be used by the network node to predict the CSI of a future time, thereby mitigating the channel aging problem for UEs moving at medium-to-high speed.

[0122] The above potential solution based on including Doppler parameters in the CSI report may require changes in the 3GPP specifications because new elements or reporting quantities in the CSI report need be introduced. Furthermore, new CSI-RS transmission patterns may also be needed to enable accurate Doppler parameters estimation in the UE. It can thus also be computationally demanding for the UE to perform Doppler parameters estimation due to its limited processing power and battery life.

[0123] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. The embodiments of the present disclosure include methods and systems for predicting the CSI based on Doppler parameters estimation. To address the aforementioned challenges associated with UEs having medium-to-high speed mobilities, the present disclosure provides a combination of a method performed by a network node (e.g., gNB) combined with a CSI report from one or more UEs.

[0124] In various embodiments of the present disclosure, the network node estimates Doppler parameters jointly in the beam angle and time delay domain and combines this estimation with an NR Rel-17 Type II port-selection CSI report from a UE to predict the CSI in a future time step. In particular, a CSI-RS port in the Rel-17 Type II port-selection framework represents a beam angle with a pre-compensated time delay associated to a channel cluster. The channel is typically sparse in this joint domain. As a result, certain Doppler parameters like the Doppler spread for a single CSI-RS port is typically less than the Doppler spread for a composite channel. As described above, a composition channel refers to a channel comprising multiple clusters. Therefore, it is a relatively simpler estimation task to predict the CSI like a channel coefficient for a single CSI-RS port compared to estimating it for a composite channel. For example, in one scenario, when a channel for a single port has only a single Doppler shift, the CSI per port can simply be predicted using extrapolation with a linear phase progression over time. The composite channel can then be predicted in the network node by jointly utilizing the predictions for each individual CSI-RS port (e.g., through a linear combination of the ports). The systems and methods for predicting CSI at a future time step described in this disclosure can be used to process more challenging and complex scenarios, as described in greater detail below.

[0125] Figure 10 illustrates an example flowchart of a method 1000 for predicting CSI at a future time step. Method 1000 can be performed by a communication system (e.g., system 100) comprising a network node and one or more UEs. Certain steps of method 1000 are performed by a network node and certain steps are performed by a UE. In describing the methods, a network node can be any network node described herein (e.g., network node 300) and UE can be any UE described herein (e.g., UE 200). At a high level, the methods described herein utilize the time domain CSI (e.g., Doppler shift) associated with each beam angle and time delay cluster and then use this CSI together with the associated CSI report from the UE to predict CSI for a composite channel (e.g., a channel comprising multiple clusters). The process flow shown in Figure 10 may be performed in any order and may omit any of the steps in the process or may combine some of the steps in part or in whole, with other steps in part or in whole.

[0126] With reference to Figure 10, at step 1002, a network node configures a port selection codebook (e.g., Type II port selection codebook) and one or more CSI-RS resources of one or more CSI-RS ports (e.g., N ports, where N is integer greater than or equal to one), and one or more SRS resources for a UE (or each of multiple UEs). As described above, for example, a network node can configure the UE with multiple CSI reporting settings and multiple CSI-RS resource settings. Each resource setting can contain multiple resource sets, and each resource set can contain up to 8 CSI-RS resources. For each CSI reporting setting, a UE feeds back a CSI report. Each CSI reporting setting can include, among other things, a CSI-RS resource set for channel measurement, CSI parameters to be reported, and codebook types (e.g., Type I or II).

[0127] At step 1004, the network node sends to the UE a configuration of one or more reference signals (e.g., SRS). In some embodiments, the configuration of the one or more reference signals includes a configuration for measuring a burst of CSI-RS. A burst of CSI-RS may include several CSI reference signals in a short period of time One such example burst of CSI-RS reference signals is shown in Figure 11A. At step 1006, the UE receives the configuration of the one or more reference signals (e.g., SRS). At step 1008, the UE sends one or more uplink reference signals (e.g., SRS) to the network node based on the configuration. At step 1010, the network node receives the reference signals, based on which it can estimate a power spectrum of the channel using multiple beam angles and time delays of the uplink multi-antenna radio channel representing the scattering clusters of the channel for the UE. It is understood that this can be performed for each UE if there are multiple UEs. [0128] At step 1012, the network node estimates the UL channel and performs precoding of a plurality of CSI-RS ports. Step 1012, together with step 1020 described below, are performed by the network node to estimate Doppler parameters for selected CSI-RS ports. For example, based on the reference signals from the UE, the network node estimates the UL channel and performs CSI-RS precoding with delay pre-compensation for each CSI-RS port. The network node estimates the power spectrum of the UL channel based on the beam angles and time delays of the propagation associated with the channel using pre -configured UL reference signals, e.g., SRS and/or DM-RS transmissions from each of one or more UEs. The power spectrum can be calculated based on, e.g., a discrete Fourier Transform (DFT) of the channel in the antenna domain and an inverse discrete Fourier Transform (IDFT) of the channel in the frequency domain. From the estimated power spectrum of the channel, the network node selects the dominant channel clusters and associates (e.g., allocates) a CSI-RS port (for subsequent CSI-RS transmission) to each of dominant clusters in the estimated power spectrum of the channel (e.g., one port per polarization). In one example, a CSI-RS port is allocated to a strongest peak (or cluster) in a power spectrum of the channel. The dominant channel clusters can alternatively be estimated by other methods, e.g., parametric methods like maximum likelihood, Space-alternating generalized expectationmaximization (SAGE), expectation-maximization (EM), etc. At step 1013, the network node sends to the UE a configuration of the CSI-RS resources for channel measurements. For example, the network node sends configurations including precoded CSI-RS ports using delay precompensation, for example, as described above regarding FDD-based reciprocity operation and Rel-17 Type II port selection codebook.

[0129] At step 1014, the UE receives from the network node the configuration of CSI-RS resources for channel measurements. At step 1015, the UE performs channel measurement based on the received configuration. For example, the UE measures the precoded CSI-RS ports. Specifically, as described above, based on the received configuration of CSI-RS resources for channel measurements, the UE can determine a set of frequency domain basis vectors and a plurality of sets of combination coefficients per layer at one or more time steps for combining the CSI-RS ports and the set of frequency domain basis vectors. Furthermore, the UE can select all or a subset of the CSI-RS ports. A CSI report can thus include, for example, an indication of a set of frequency domain basis vectors, an indication of a plurality of sets of combination coefficients per layer at one or more time steps for combining the CSI-RS ports and the set of frequency domain basis vectors, an indication of one or more selected CSI-RS ports, and an indication of a type II precoding matrix based on prioritization rules. For example, if the PUSCH allocation for carrying the CSI is not sufficient for all the CSI reporting content, then certain prioritization can be performed based on prioritization rules. The prioritization rules are described in greater detail below. It is understood that the CSI report can include more or fewer indications as described above. In some embodiments, the CSI report can be a Type II port-selection CSI report (e.g., a Rel-16/17/18 Type II). At step 1016, the UE sends a CSI report to the network node. It is understood that if there are multiple UEs, each UE can perform channel measurements based on a respectively received configuration, and send a respective CSI report to the network node.

[0130] At step 1018, the network node receives the CSI report, which may include various indications and/or information. Among the indications, the network node may receive an indication of one or more CSI-RS ports selected by the UE.

[0131] At step 1020, the network node obtains Doppler parameters for each selected CSI-RS ports. At step 1022, the network node predicts, based on the obtained Doppler parameters for each selected CSI-RS port, CSI for a channel associated with one or more selected CSI-RS ports, at a future time step. The various embodiments of obtaining of the Doppler parameters (step 1020) and predicting CSI at the future time step (step 1022) are described in greater detail below.

[0132] At step 1024, the network node determines a precoder for the UE based on the predicted CSI at the future time step. For example, the predicted CSI at the future time step can be used for PDSCH precoding or MU-MIMO scheduling.

[0133] Various embodiments of obtaining of the Doppler parameters (step 1020) and predicting CSI at the future time step (step 1022) are now described in greater detail. In some embodiments, for each selected CSI-RS port in the CSI report, the network node estimates the corresponding Doppler parameters (also referred to as Doppler domain channel properties) including, e.g., Doppler shift and/or Doppler spread. The Doppler parameters can be estimated based on reference signals like SRS and/or demodulation reference signal (DM-RS). For instance, the Doppler domain channel property can be estimated from the last SRS and/or DM-RS transmission, or multiple previous SRS/DM-RS transmissions. Specifically, Doppler domain channel properties can be estimated by processing over the received reference symbols in a slot, e.g., by computing the Fourier transform of the temporal autocorrelation function to get the Doppler spectrum and/or by comparing the phase of the received signal at different time instances. [0134] As described above, at step 1012, for obtaining the Doppler parameters, the network node estimates the UL channel in the beam angle and time delay domain based on pre-configured UL reference signals at a plurality of time steps (also referred to as time instances). In one embodiment, at step 1012, the estimated channel at a plurality of time instances is transformed into the beam domain (e.g., by computing a DFT). By comparing the estimates at two (or more) time instances, Doppler parameters are estimated for each beam. Then, at step 1020, the beams (and the corresponding estimates of the Doppler parameters) may be selectively kept according to the received CSI report (for example, network node keeps only the beams that are included in the CSI report).

[0135] Examples of reference signals that could be used to estimate the Doppler parameters are provided below.

[0136] In one embodiment, the network node estimates Doppler parameters based on singlesymbol DM-RS with 1 — 3 additional DM-RS symbols, which results in multiple DM-RS symbols in a slot. In one embodiment, the network node estimates Doppler parameters based on doublesymbol DM-RS with 0 — 1 additional DM-RS symbols, which results in multiple DM-RS symbols in a slot.

[0137] In one embodiment, the network node estimates Doppler parameters based on SRS transmission spanning a plurality of consecutive SRS symbols using one or more of repetition, frequency hopping (FH), resource-block level partial frequency sounding (RPFS) or a combination of repetition, FH, and RPFS. In one embodiment, the network node estimates Doppler parameters based on SRS transmission with multiple symbols in one slot, where a given SRS port is present in at least two nonconsecutive OFDM symbols, e.g., with a gap of one or more OFDM symbols in between.

[0138] In one embodiment, the network node configures an SRS transmission with a single symbol. The SRS has a comb structure, which results in a time-domain SRS signal that includes two or more identical parts. Due to such a comb structure, it is possible to estimate Doppler parameters from a single symbol by comparing the phase of the received signal over these two or more parts. In some embodiments, such a comb structure is also used in type-1 DM-RS. The DM- RS can thus also be used for the network node to estimate Doppler parameters.

[0139] In one embodiment, the network node uses the SRS from multiple slots to perform Doppler parameters estimation. In this case, the UE can maintain phase coherency between slots in the SRS transmissions. Hence, the UE may have indicated in advance, using UE-capability signaling, that it has capability to maintain phase coherency between slots. It is understood that if there are multiple UEs, each UE can perform the same or similar.

[0140] In one embodiment, the network node estimates the Doppler parameters (e.g., Doppler domain channel properties) when the SRS and/or DM-RS transmissions are received. For example, with reference to Figure 10, at step 1012, as described above, the network node can estimate the Doppler parameters for each CSI-RS port since the network node does not know at this stage which ports that will be selected by the UE. The network node can save the estimates for use at a subsequent step (e.g., step 1020 for obtaining Doppler parameters for UE selected CSI- RS ports). In some of the embodiments described above (e.g., at step 1015), the UE selects the CSI-RS ports, and the network node can then obtain the Doppler parameters for each of the UE selected CSI-RS ports (e.g., at step 1020).

[0141] In one embodiment, “raw” channel estimates are computed when SRS and/or DM-RS transmissions are received and are saved for computing Doppler parameters. In this case, the network node only needs to estimate the Doppler parameters for the CSI-RS ports that have been reported by the UE (or each of multiple UEs).

[0142] The Doppler parameters can be estimated in different ways. One way is to compute the Doppler spectrum by computing the Fourier transform of the temporal autocorrelation function estimated over symbols, sub-symbols and/or slots. From the Doppler spectrum, Doppler parameters like Doppler spread and dominant Doppler shift can be extracted. Doppler parameters can alternatively be estimated using other parametric estimation methods, e.g., the maximum likelihood method.

[0143] In other embodiments, the UE can estimate the Doppler parameters and send the estimation to the network node in, for example, the CSI report. In some embodiments, the UE and the network node may each estimate certain Doppler parameters.

[0144] With reference to Figure 10, at step 1022, the network node predicts, based on the obtained Doppler parameters for each selected CSI-RS port, CSI at a future time step for a channel associated with the selected one or more CSI-RS ports. In particular, the network node uses the estimated Doppler parameters together with the CSI report from the UE (or each of multiple UEs) to predict the CSI at a future time step. In some embodiments, the network node predicts the CSI for the channel at the future time step based on the predicted CSI at the future time step for each selected CSI-RS port. Based on the precited CSI for each CSI-RS port, the network node can predict the CSI associated with multiple CSI-RS ports (e.g., composite channel state information) by combining the predicted CSI of all selected CSI-RS ports. For example, the network node can perform a linear combination of the predictions for each of the individual CSI-RS ports to compute the predicted CSI for a composite CSI. It is understood that the network node can also compute CSI for a channel associated with the selected one or more CSI-RS ports at the current time step, using the Doppler parameters.

[0145] In some embodiments, using the predicted CSI at a future time step, the network node determines a precoding matrix per layer at the future time step based on a set of spatial domain basis vectors, a set of frequency domain basis vectors, and a set of combination coefficients. The set of combination coefficients is for the future time step and based on the obtained Doppler parameters. For example, the PMI for a given layer reported by the UE (or each of multiple UEs) at time t, denoted by W (t) G

[0146] In the above expression [2], 14^ (t) G (C^PxK1 is a port-selection matrix containing spatial domain basis vector, where P and K₁ are the number of configured and selected CSI-RS ports, respectively. 14^ (t) G ( ^N3^xM is an FD compression matrix with DFT columns, where M and N₃ are the number of selected FD basis vectors and number of subbands, respectively. IV₂ (t) G ( ^KI^XM i_{s a} matrix containing linear combination coefficients for the corresponding ports and FD basis vectors, and c_{fe m}(t) is the (k, m)-th entry of W₂ (t), for k = 0,

— 1 and m =

0, ... , M - 1.

[0147] Because 14^ (t) and 14^ (t) are long-term channel properties that do not tend to change rapidly, they can be treated as fixed for a predetermined period of time. Then, the PMI for a future time step t + At, denoted by W(t + At), can be calculated by the following expression.

In expression [3], 14^ (t + At) is updated based on the estimated Doppler parameters. In one scenario, when the channel coefficient for a pair of CSI-RS port and FD basis vector has only a single Doppler shift, the coefficient can be predicted using extrapolation with a linear phase progression over time. Specifically, the linear combination coefficient for CSI-RS port k and FD basis vector m, at time t, can be denoted by the following expression.

[0148] In expression [4], f_{k m} is the estimated Doppler shift for CSI-RS port k and FD basis vector m. More generally, other prediction methods can be used to predict the channel for each port. Such prediction methods include, e.g., autoregressive model prediction, Kalman filtering, etc. Some of these methods are described above or can be understood by one of ordinary skill in the art. Methods based on machine learning can also be used.

[0149] Because there is a one-to-one correspondence between the Doppler spectrum and the temporal autocorrelation function via the Fourier transform, in some embodiments, the network node can use estimated time-domain properties in the CSI prediction instead of using the Doppler domain parameters.

[0150] In some embodiments, the Doppler shifts can be tracked over time to improve the channel prediction. For example, if the UE (or each of multiple UEs) is moving along a railway or highway and the Doppler spread is low, it can be relatively easy to track the Doppler variation over time.

[0151] In some embodiments, the Doppler parameters can also be reported by the UE (or each of one or more UEs) via a CSI report. The CSI report can, for example, includes both Rel- 17 Type II CSI and Doppler parameters for the selected CSI-RS ports. In some embodiments, the Doppler parameters may be obtained only via a CSI report, which does not require the network node to estimate. In some embodiments, the network node may still estimate the Doppler parameters and combine the estimated and UE reported Doppler parameters to improve the estimation accuracy. [0152] In some embodiments, more than one time instance of CSI-RS may be configured for a UE (or each of one or more UEs) to report type II CSI. An example is illustrated in Figure 11 A, where a CSI-RS resource is configured in three time steps ti, t2, and ts for a CSI report. As described above, a time step is also referred to as a time instance. The different time steps may be in different OFDM symbols within a same slot, or in different slots. In some embodiments, to improve the performance, the time steps may be non-uniformly spaced, for example, t₂ — U = 2 and t₃ — t₂ = 3. For each time step, the UE (or each of one or more UEs) can determine a type II precoding matrix for each MIMO layer as the following expression.

[0153] In the above expression [25], 14^ (t) and I4^(t) may change slowly when the time window t₃ — U is small,

Thus, only W₂(t₂) and W₂ (t₃) need to be reported for CSI at time steps t₂ and t₃, respectively. Therefore, in one embodiment, the UE (or each of one or more UEs) reports a type II precoding matrix, ^(U), associated with CSI-RS at time step U plus W₂ (t₂) and W₂ t₃). Each element of W₂ includes an amplitude and phase component. When the time window t₃ — t₁ is small, the amplitude should not, or may not, change much. Thus, in some embodiments, the phase parts of W₂(t₂) and W₂(t₃) are reported. With

and W₂(t₃). the network node can derive the phase change for each W₂ coefficient over time instances {t_1; t₂, t₃} and thus estimate the underlying corresponding Doppler frequency or phase slope over the time period based on some criteria such as mean square error (MSE). An example is illustrated in Figure 11B. The estimated Doppler frequency or phase slope can then be used to predict the corresponding W₂ coefficient in a future time step. Alternatively, instead of reporting W₂ (t₂) and W₂(t₃). the phase difference of each coefficient of W₂ in different time steps with respect to the first time step is reported. In a further embodiment, the phase slope of each coefficient of W₂ over the time window is reported. [0154] In some embodiments, when the different time steps are in close proximity in the time domain (e.g., time steps t₁, t₂, and t₃ are in the same slot or in adjacent slots), the UE (or each of one or more UEs) may report the related CSI content in a single PUSCH transmission. That is, W^G),

W ₂(t₃) as described in the above example embodiments can be reported as part of a single PUSCH. In some embodiments, the same subset of coefficients is selected via a single non-zero coefficient bitmap (i.e., G,7,J) reported as a part of the first part of the CSI report. By indicating K^'^z 1’s in the single non-zero coefficient bitmap, the same subset of coefficients (e.g., coefficients corresponding to the same set of CSI-RS ports k and FD bases vector m combinations) are reported for each of W₂ (t^), W₂ t₂~), and W₂ (t₃) .

[0155] In some embodiments, if the PUSCH allocation for carrying the CSI is not sufficient for all the CSI reporting content among W₂ (t^, W₂ (t₂), and W₂ (t₃), some prioritization rules may be specified in 3GPP specifications. Since W₂ t₁), W₂ t₂), and W₂(t₃) are reported as a part of the second part of a CSI report, a priority may be defined such that W₂ (G) has higher priority over W₂(t₂) and W₂(t₃~) and W₂(t₂) has higher priority over W₂(t₃). Hence, in one example, if there are no sufficient resources for reporting all three of W₂(t₁), W₂(t₂), and W₂(t₃) , then only coefficients corresponding to W₂(G) and MGCG) ^are reported and coefficients corresponding to W₂(t₃) are not reported. In another example, only coefficients corresponding to W₂(G) ^are reported and coefficients corresponding to W₂(t₂) and W₂(t₃)arc not reported.

[0156] In existing W₂, the phase part is quantized in a granulation of 2TT/16 or 22.5°, which may be considered coarse in cases where the time window t₃ —

is small and/or Doppler frequency is small. Thus, in some embodiments, a finer granularity, e.g., 2TT/64 may be used in the phase related report.

[0157] In some embodiments, predicting CSI can be applied to multiple transmission points (TRP) simultaneously, so that the network node is provided with the Doppler parameters (i.e., time variation) between the UE (or each of one or more UEs) and each of the TRPs. The network node then selects one of the TRPs (or a subset of the TRPs) to be used for PDSCH transmission to the each of one or more UEs based on the set of estimated Doppler parameters. For example, it can select, (or prioritize) the TRP that has the smallest absolute Doppler shift value for PDSCH transmission. This is because the CSI from the UE (or each of one or more UEs) associated with this TRP is expected to be valid for a longer time duration. Thus, the CSI is more accurate at the time of PDSCH scheduling.

[0158] As described above, using the CSI for a composite channel, the network node computes a precoder for each of one or more UEs to be used for, e.g., a MU-MIMO scheduled transmission of PDSCH. [0159] In the above described embodiments, the CSI report can be a port-selection CSI report (e.g., a Type II port-selection CSI report according to Rel-16, 17, 18, or other past and future releases).

[0160] Certain embodiments of the present disclosure may provide one or more of the following technical advantage(s), including more accurate CSI for time-varying channels. This can give better precoding performance and thereby higher throughput and capacity.

[0161] Figure 12 is a flow chart illustrating a method 1200 performed by a network node (node 110A or HOB). The process flow may be performed in any order and may omit any of the steps in the process or may combine some of the steps in part or in whole, with other steps in part or in whole. At step 1202, the network node sends a configuration of one or more CSI-RS resources for channel measurements to a UE. This step is similar to, for example, step 1013 of Figure 10 and is thus not repeatedly described.

[0162] At step 1204, the network node receives, from the UE, a CSI report. As described above, the CSI report includes an indication of the one or more CSI-RS ports selected by the UE. In some embodiments, the CSI report may further include an indication of a set of frequency domain basis vectors, an indication of a plurality of sets of combination coefficients per layer for combining one or more CSI-RS ports, and an indication of Doppler parameters for each selected CSI-RS port. The one or more time steps for which the plurality of sets of combination coefficients are included in the CSI report can be selected based on prioritization rules of communication resources, as described above. These contents of the CSI report are all described above in greater detail and thus not repeatedly described. As also described above, the CSI report in some embodiments includes the Doppler parameters. In other embodiments, the CSI report does not include Doppler parameters and the network node estimate the Doppler parameters.

[0163] At step 1206, the network node predicts, based on the obtained Doppler parameters for each selected CSI-RS port and the CSI report, CSI for a channel associated with the one or more CSI-RS ports at a future time step. Step 1206 is similar to step 1022 described above for Figure 10, and is thus not repeatedly described.

[0164] Figure 13 is a flow chart illustrating a method 1300 performed by UE (UE 112A or 112B). The process flow may be performed in any order and may omit any of the steps in the process or may combine some of the steps in part or in whole, with other steps in part or in whole. At step 1302, the UE receives a configuration of one or more CSI-RS resources for channel measurements. At step 1304, the UE performs the channel measurements on the one or more CSI- RS resources according to the received configuration. The steps 1302 and 1304 are similar to steps 1014 and 1015 respectively of Figure 10 and is thus not repeatedly described. [0165] At step 1306, the UE determines a set of frequency domain basis vectors (e.g., IF) and a plurality of sets of combination coefficients (W2) per layer for combining the CSI-RS ports and the set of frequency domain basis vectors for multiple time steps. The determination of the Wf and W2 is described above in greater details and thus not repeatedly described here.

[0166] At step 1308, the UE sends a CSI report to the network node. As described above, the CSI report includes an indication of the one or more CSI-RS ports selected by the UE. In some embodiments, the CSI report may further include an indication of a set of frequency domain basis vectors, and an indication of a plurality of sets of combination coefficients per layer for combining one or more CSI-RS ports. The one or more time steps for which the plurality of sets of combination coefficients are included in the CSI report can be selected based on prioritization rules of communication resources, as described above. These contents of the CSI report are all described above in greater detail and thus not repeatedly described. As also described above, the CSI report in some embodiments includes the Doppler parameters. In other embodiments, the CSI report does not include Doppler parameters and the network node estimates the Doppler parameters.

[0167] The foregoing specification is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the teachings disclosed herein is not to be determined from the specification, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope of the teachings. Those skilled in the art could implement various other feature combinations without departing from the scope of the claims.

Claims

37 CLAIMS WHAT IS CLAIMED IS:

1. A method performed by a network node, the method comprising: receiving an indication of one or more channel state information reference signal (CSI-RS) ports selected by a user Equipment (UE); obtaining Doppler parameters for each selected CSI-RS port; and predicting, based on the obtained Doppler parameters for each selected CSI-RS port, channel state information (CSI) at a future time step for a channel associated with the selected one or more CSI-RS ports.

2. The method of claim 1, further comprising determining a precoder for the UE based on the predicted CSI at the future time step.

3. The method of claim 1 , wherein obtaining the Doppler parameters comprises receiving the Doppler parameters from the UE, in a CSI report.

4. The method of claim 1, wherein obtaining the Doppler parameters comprises: receiving one or more uplink reference signals from the UE; estimating a power spectrum of the channel based on multiple beam angles and time delays of propagation associated with the channel based on the one or more reference signals received from the UE; and associating a CSI-RS port to each of dominant clusters in the estimated power spectrum of the channel. estimating the Doppler parameters for the selected one or more CSI-RS ports.

5. The method of claim 4, further comprising sending, to the UE, a configuration of the one or more downlink reference signals.

6. The method of claim 5, wherein the configuration of one or more downlink reference signals comprises a configuration for measuring a burst of CSI-RS.

7. The method of claims 4-6, wherein estimating the power spectrum of the channel based on multiple beam angles and time delays is based on a discrete Fourier Transform (DFT) of the channel in an antenna domain and an inverse discrete Fourier Transform (IDFT) of the channel in a frequency domain.

8. The method of any of claims 4-7, further comprising: selecting one or more dominant clusters in the estimated power spectrum of the channel based on the multiple beam angles and time delays of the propagation clusters associated with the channel; 38 precoding a plurality of CSI-RS ports based on the selected one or more dominant clusters to obtain a port selection codebook; and sending to the UE a configuration of the CSI-RS resources for channel measurement based on the port selection codebook.

9. The method of any of claims 1-8, further comprising: receiving, from the UE, a CSI report including the indication of one or more selected (CSI- RS) ports, the CSI report further comprises an indication of a set of frequency domain basis vectors, and a plurality of sets of combination coefficients per layer for combining the CSI-RS ports.

10. The method of any of claims 1-9, wherein obtaining the Doppler parameters for each selected CSI-RS port comprises, for each selected CSI-RS port: estimating the Doppler parameters based on at least one of one or more most-recently received reference signals or previously received reference signals.

11. The method of claim 10 wherein the at least one of one or more most-recently received reference signals or previously received reference signals comprises: a single -symbol demodulation reference signal (DM-RS) with 1-3 additional DM-RS symbols, wherein a slot has multiple DM-RS symbols.

12. The method of claim 10, wherein the at least one of one or more most-recently received reference signals or previously received reference signals comprises: a double-symbol DM-RS with 0-1 additional DM-RS symbols, wherein a slot has multiple DM-RS symbols.

13. The method of claim 10 wherein the at least one of one or more most-recently received reference signals or previously received reference signals comprises: a plurality of consecutive sounding reference signal (SRS) symbols based on one or more of repetition, frequency hopping (FH), and resource-block level partial frequency sounding (RPFS).

14. The method of claim 10 wherein the at least one of one or more most-recently received reference signals or previously received reference signals comprises: an SRS transmission with multiple symbols in one slot, wherein an SRS port is present in at least two non-consecutive OFDM symbols.

15. The method of claim 10 wherein the at least one of one or more most-recently received reference signals or previously received reference signals comprises: sounding reference signals from multiple slots.

16. The method of any of claims 1-15, wherein obtaining the Doppler parameters for each selected CSI-RS port comprises: determining a Doppler spectrum by computing a Fourier transform of a temporal autocorrelation function estimated over at least one of symbols, sub-symbols, and slots of a received reference signal; extracting the Doppler parameters from the Doppler spectrum.

17. The method of any of claims 1-15, wherein predicting the channel information state for the channel associated with the selected one or more CSI-RS ports comprises: predicting the channel state information for the channel at the future time step based on the predicted channel state information at the future time step for each selected CSI-RS port.

18. The method of claim 17, further comprising, based on the predicted channel state information at the future time step: determining a precoding matrix per layer based on a set of spatial domain basis vectors, a set of frequency domain basis vectors, and a set of combination coefficients, the set of combination coefficients being for the future time step and based on the obtained Doppler parameters.

19. The method of claims 17 or 18, wherein predicting the channel information for the channel at the future time step based on the predicted channel state information for a future time step for each selected CSI-RS port comprises: combining the predicted channel state information of all selected CSI-RS ports.

20. A method performed by a network node, the method comprising: sending a configuration of one or more channel state information reference signal (CSI- RS) resources to a user equipment (UE); receiving, from the UE, a CSI report comprising: an indication of a set of frequency domain basis vectors, an indication of a plurality of sets of combination coefficients per layer at one or more time steps for combining one or more CSI-RS ports and the set of frequency domain basis vectors, an indication of the one or more CSI-RS ports selected by the UE, and an indication of Doppler parameters for each selected CSI-RS port, wherein the one or more time steps for which the plurality of sets of combination coefficients are included in the CSI report are selected based on prioritization rules of communication resources; and predicting, based on the obtained Doppler parameters for each selected CSI-RS port and the CSI report, channel state information for a channel associated with the one or more CSI-RS ports at a future time step.

21. A method performed by a user equipment (UE) for channel state information (CSI) reporting, the method comprising: receiving a configuration of one or more CSI reference signal (CSI-RS) resources for channel measurements; performing the channel measurements on the one or more CSI-RS resources according to the received configuration; determining a set of frequency domain basis vectors and a plurality of sets of combination coefficients per layer at multiple time steps for combining the CSI-RS ports and the set of frequency domain basis vectors; and sending a CSI report to the network node, the CSI report comprising: the indication of the set of frequency domain basis vectors, the indication of the plurality of sets of combination coefficients per layer at the multiple time steps for combining the CSI-RS ports and the set of frequency domain basis vectors, and an indication of one or more selected (CSI-RS) ports, wherein the multiple time steps for which the plurality of sets of combination coefficients are included in the CSI report are selected based on prioritization rules of communication resources.

22. The method of claim 21, further comprising selecting the one or more CSI-RS ports.

23. The method of claim 21 or 22, further comprising sending one or more reference signals to the network node.

24. The method of claim 23, wherein the one or more reference signals comprise: a single-symbol demodulation reference signal (DM-RS) with 1-3 additional DM-RS symbols, wherein a slot has multiple DM-RS symbols.

25. The method of claim 23, wherein the one or more reference signals comprise: a double-symbol DM-RS with 0-1 additional DM-RS symbols, wherein a slot has multiple DM-RS symbols.

26. The method of claim 23, wherein the one or more reference signals comprise: a plurality of consecutive sounding reference signal (SRS) symbols based on one or more of repetition, frequency hopping (FH), and resource-block level partial frequency sounding (RPFS).

27. The method of claim 23, wherein the one or more reference signals comprise: an SRS transmission with multiple symbols in one slot, wherein an SRS port is present in at least two non-consecutive OFDM symbols.

28. The method of claim 23, wherein the one or more reference signals comprise: sounding reference signals from multiple slots.

29. A network node comprising: a transceiver, a processor, and a memory, said memory containing instructions executable by the processor whereby the network node is operative to perform the method of any one of claims 1 to 20.

30. User equipment (UE) for performing channel state information (CSI) reporting, comprising: a transceiver, a processor, and a memory, said memory containing instructions executable by the processor whereby the UE is operative to perform the method any one of claims 21-28.

31. A computer program product comprising a non-transitory computer readable storage medium having computer readable program code embodied in the medium, the computer readable program code comprising computer readable program code to operate according to any of the methods of any one of claims 1 to 28.