WO2021097588A1

WO2021097588A1 - Enhancements for analog feedforward channel state information reference signal

Info

Publication number: WO2021097588A1
Application number: PCT/CN2019/119068
Authority: WO
Inventors: Liangming WU; Chenxi HAO; Yu Zhang; Qiaoyu Li; Hao Xu; Wanshi Chen
Original assignee: Qualcomm Incorporated
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2021-05-27

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a base station may provide a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information. The CSI-RS bundling information may identify at least one of a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports. The base station may transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information. Numerous other aspects are provided.

Description

ENHANCEMENTS FOR ANALOG FEEDFORWARD CHANNEL STATE INFORMATION REFERENCE SIGNAL

TECHNICAL FIELD

Aspects of the technology described below generally relate to wireless communication and to techniques and apparatuses for enhancements for analog feedforward channel state information reference signal (CSI-RS) . Some techniques and apparatuses described herein enable and provide wireless communication devices and systems configured for reducing CSI-RS overhead and improving CSI-RS channel estimation accuracy.

INTRODUCTION

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like) . Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, orthogonal frequency-division multiple access (OFDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, time division synchronous code division multiple access (TD-SCDMA) systems, and Long Term Evolution (LTE) . LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by the Third Generation Partnership Project (3GPP) .

A wireless communication network may include a number of base stations (BSs) that can support communication for a number of user equipment (UEs) . A user equipment (UE) may communicate with a base station (BS) via the downlink and uplink. The downlink (or forward link) refers to the communication link from the BS to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the BS. A BS may be referred to as a Node B, a gNB, an access point (AP) , a radio head, a transmit receive point (TRP) , a new radio (NR) BS, a 5G Node B, and/or the like.

Multiple access technologies have been adopted in various telecommunication standards. Wireless communication standards provide common protocols to enable different devices (e.g., user equipment) to communicate on a municipal, national, regional, and even global level. New radio (NR) , which may also be referred to as 5G, is a set of enhancements to the LTE mobile standard promulgated by the Third Generation Partnership Project (3GPP) . As demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE and NR technologies. These improvements can apply to other multiple access technologies and the telecommunication standards that employ these technologies.

BRIEF SUMMARY OF SOME EXAMPLES

The following summarizes some aspects of the present disclosure to provide a basic understanding of the discussed technology. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. The purpose of the summary is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.

In an analog feedforward framework, a base station may precode CSI-RS with both a spatial domain (SD) basis and a frequency domain (FD) basis. However, this requires full and accurate channel information in order to estimate the spatial beam and delay path domain information, which may not be readily achievable in some scenarios. Further, the number of CSI-RS ports may be increased with the increasing of the SD and FD (SD/FD) precoded basis. Some aspects described herein provide techniques and apparatuses for enhancements for analog feedforward CSI-RS. In some aspects, the enhancements include multiplexing (also referred to herein as bundling) SD/FD precoded CSI-RS ports, thereby enabling improved CSI-RS channel estimation accuracy and/or reducing CSI-RS overhead.

In some aspects, a method of wireless communication, performed by a base station, may include providing a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports; and transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.

In some aspects, a method of wireless communication, performed by a UE, may include receiving a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; receiving a CSI-RS on the group of bundled CSI-RS ports; and recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.

In some aspects, a base station for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to provide a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; and transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.

In some aspects, a UE for wireless communication may include memory and one or more processors operatively coupled to the memory. The memory and the one or more processors may be configured to receive a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; receive a CSI-RS on the group of bundled CSI-RS ports; and recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a base station, may cause the one or more processors to: provide a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; and transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.

In some aspects, a non-transitory computer-readable medium may store one or more instructions for wireless communication. The one or more instructions, when executed by one or more processors of a UE, may cause the one or more processors to: receive a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; receive a CSI-RS on the group of bundled CSI-RS ports; and recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.

In some aspects, an apparatus for wireless communication may include means for providing a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; and means for transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.

In some aspects, an apparatus for wireless communication may include means for receiving a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; means for receiving a CSI-RS on the group of bundled CSI-RS ports; and means for recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.

Aspects generally include a method, apparatus, system, computer program product, non-transitory computer-readable medium, user equipment, base station, wireless communication device, and/or processing system as substantially described herein with reference to and as illustrated by the accompanying drawings and specification.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purposes of illustration and description, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the above-recited features of the present disclosure can be understood in detail, a more particular description is provided herein, with some aspects of the disclosure being illustrated in the appended drawings. However, the appended drawings illustrate only some aspects of this disclosure and are therefore not to be considered limiting of the scope of the disclosure. The same reference numbers in different drawings may identify the same or similar elements.

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a base station in communication with a UE in a wireless communication network, in accordance with various aspects of the present disclosure.

Fig. 3 is a diagram illustrating correlation between FD precoded CSI-RS ports according to an analog feedforward framework, in accordance with various aspects of the present disclosure.

Figs. 4A-4C are diagrams associated with enhancements for analog feedforward CSI-RS, in accordance with various aspects of the present disclosure.

Fig. 5 is a diagram illustrating an example process performed, for example, by a base station, in accordance with various aspects of the present disclosure.

Fig. 6 is a diagram illustrating an example process performed, for example, by a user equipment, in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

Several aspects of telecommunication systems will now be presented with reference to various apparatuses and techniques. These apparatuses and techniques will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and/or the like (collectively referred to as “elements” or “features” ) . These elements may be implemented using hardware, software, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

While some aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and/or other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, and/or the like) . While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including one or more antennas, RF-chains, power amplifiers, modulators, buffers, processors, interleavers, adders/summers, and/or the like) . It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes, and constitution.

Fig. 1 is a diagram illustrating a wireless network 100 in which aspects of the present disclosure may be practiced. The wireless network 100 may be an LTE network or some other wireless network, such as a 5G or NR network. The wireless network 100 may include a number of BSs 110 (shown as BS 110a, BS 110b, BS 110c, and BS 110d) and other network entities. A BS is an entity that communicates with user equipment (UEs) and may also be referred to as a base station, a NR BS, a Node B, a gNB, a 5G node B (NB) , an access point, a transmit receive point (TRP) , and/or the like. Each BS may provide communication coverage for a particular area (e.g., a fixed or changing geographical area) . In some scenarios, BSs 110 may be stationary or non- stationary. In some non-stationary scenarios, mobile BSs 110 may move with varying speeds, direction, and/or heights. In 3GPP, the term “cell” can refer to a coverage area of a BS 110 and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or another type of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. Additionally, or alternatively, a BS may support access to an unlicensed RF band (e.g., a Wi-Fi band and/or the like) . A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG) ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in Fig. 1, a BS 110a may be a macro BS for a macro cell 102a, a BS 110b may be a pico BS for a pico cell 102b, and a BS 110c may be a femto BS for a femto cell 102c. A BS may support one or multiple (e.g., three) cells. The terms “eNB” , “base station” , “NR BS” , “gNB” , “TRP” , “AP” , “node B” , “5G NB” , and “cell” may be used interchangeably herein.

In some aspects, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS. In some aspects, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the wireless network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, and/or the like using any suitable transport network. In other scenarios, BSs may be implemented in a software defined network (SDN) manner or via network function virtualization (NFV) manner.

Wireless network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., a BS or a UE) and send a transmission of the data to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in Fig. 1, a relay station 110d may communicate with macro BS 110a and a UE 120d in order to facilitate communication between BS 110a and UE 120d. A relay station may also be referred to as a relay BS, a relay base station, a relay, and/or the like.

Wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, and/or the like. These different types of BSs may have different transmit power levels, different coverage areas, and different impacts on interference in wireless network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts) .

A network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., 120a, 120b, 120c) may be dispersed throughout wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, and/or the like. A UE may be a cellular phone (e.g., a smart phone) , a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or equipment, biometric sensors/devices, wearable devices (smart watches, smart clothing, smart glasses, smart wrist bands, smart jewelry (e.g., smart ring, smart bracelet) ) , an entertainment device (e.g., a music or video device, or a satellite radio) , a vehicular component or sensor, smart meters/sensors, industrial manufacturing equipment, robotics, drones, implantable devices, augmented reality devices, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium.

Some UEs may be considered machine-type communication (MTC) or evolved or enhanced machine-type communication (eMTC) UEs. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, and/or the like, that may communicate with a base station, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, and/or may be implemented as may be implemented as NB-IoT (narrowband internet of things) devices. Some UEs may be considered a Customer Premises Equipment (CPE) . UE 120 may be included inside a housing that houses components of UE 120, such as processor components, memory components, and/or the like. These components may be integrated in a variety of combinations and/or may be stand-alone, distributed components considering design constraints and/or operational preferences.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular RAT and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, and/or the like. A frequency may also be referred to as a carrier, a frequency channel, and/or the like. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some aspects, two or more UEs 120 (e.g., shown as UE 120a and UE 120e) may communicate directly using one or more sidelink channels (e.g., without using a base station 110 as an intermediary to communicate with one another) . For example, the UEs 120 may communicate using peer-to-peer (P2P) communications, device-to-device (D2D) communications, a vehicle-to-everything (V2X) protocol (e.g., which may include a vehicle-to-vehicle (V2V) protocol, a vehicle-to-infrastructure (V2I) protocol, and/or the like) , a mesh network, and/or the like. In this case, the UE 120 may perform scheduling operations, resource selection operations, and/or other operations described elsewhere herein as being performed by the base station 110. A UE performing scheduling operations can include or perform base-station-like functions in these deployment scenarios.

As indicated above, Fig. 1 is provided merely as an example. Other examples may differ from what is described with regard to Fig. 1.

Fig. 2 shows a block diagram of a design 200 of base station 110 and UE 120, which may be one of the base stations and one of the UEs in Fig. 1. Base station 110 may be equipped with T antennas 234a through 234t, and UE 120 may be equipped with R antennas 252a through 252r, where in general T ≥ 1 and R ≥ 1. The T and R antennas may be configured with multiple antenna elements formed in an array for MIMO or massive MIMO deployments that can occur in millimeter wave (mmWave or mmW) communication systems.

At base station 110, a transmit processor 220 can carry out a number of functions associated with communications. For example, transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based at least in part on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based at least in part on the MCS (s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for semi-static resource partitioning information (SRPI) and/or the like) and control information (e.g., CQI requests, grants, upper layer signaling, and/or the like) and provide overhead symbols and control symbols. Transmit processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS) ) and synchronization signals (e.g., the primary synchronization signal (PSS) and secondary synchronization signal (SSS) ) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232a through 232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM and/or the like) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232a through 232t may be transmitted via T antennas 234a through 234t, respectively. According to various aspects described in more detail below, the synchronization signals can be generated with location encoding to convey additional information.

At UE 120, antennas 252a through 252r may receive downlink RF signals. The downlink RF signals may be received from and/or may be transmitted by one or more base stations 110. The signals can be provided to demodulators (DEMODs) 254a through 254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM and/or the like) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all R demodulators 254a through 254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 260, and provide decoded control information and system information to a controller/processor 280. A channel processor may determine reference signal received power (RSRP) , received signal strength indicator (RSSI) , reference signal received quality (RSRQ) , channel quality indicator (CQI) , and/or the like. In some aspects, one or more components of UE 120 may be included in a housing.

For uplink communications, a UE 120 may transmit control information and/or data to another device, such as one or more base stations 110. For example, at UE 120, a transmit processor 264 may receive and process data from a data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, and/or the like) from controller/processor 280. Transmit processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by modulators 254a through 254r (e.g., for DFT-s-OFDM, CP-OFDM, and/or the like) , and transmitted to base station 110. At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by UE 120. Receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to controller/processor 240. Base station 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

Controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform one or more techniques associated with enhancements for analog feedforward CSI-RS, as described in more detail elsewhere herein. For example, controller/processor 240 of base station 110, controller/processor 280 of UE 120, and/or any other component (s) of Fig. 2 may perform or direct operations of, for example, process 500 of Fig. 5, process 600 of Fig. 6, and/or other processes as described herein.

Memories

242 and 282 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

In some aspects, the UE 120 may include a variety of means or components for implementing communication functions. For example, the variety of means may include means for receiving a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; means for receiving a CSI-RS on the group of bundled CSI-RS ports; means for recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS; and/or the like.

In some aspects, the UE 120 may include a variety of structural components for carrying out functions of the various means. For example, structural components that carry out functions of such means may include one or more components of UE 120 described in connection with Fig. 2, such as antenna 252, DEMOD 254, MOD 254, MIMO detector 256, receive processor 258, transmit processor 264, TX MIMO processor 266, controller/processor 280, and/or the like.

In some aspects, the base station 110 may include a variety of means or components for implementing communication functions. For example, the variety of means may include means for providing a CSI-RS configuration including CSI-RS bundling information, wherein the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports; means for transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information; and/or the like.

In some aspects, the base station 110 may include a variety of structural components for carrying out functions of the various means. For example, structural components that carry out functions of such means may include one or more components of base station 110 described in connection with Fig. 2, such as transmit processor 220, TX MIMO processor 230, DEMOD 232, MOD 232, antenna 234, MIMO detector 236, receive processor 238, controller/processor 240, and/or the like.

As indicated above, Fig. 2 is provided merely as an example. Other examples may differ from what is described with regard to Fig. 2.

In some wireless communication systems (e.g., an NR Release-16 system) , channel state information (CSI) can be compressed in the spatial domain (SD) and the frequency domain (FD) . A base station may precode a CSI reference signal (RS) port and emulate the precoder (e.g., instead of configuring the SD and FD basis to a UE) . This may be referred to as analog feedforward.

In some cases, the CSI can be compressed as shown in the following expression:

where L is the number of SD basis, M is the number of FD basis, b is the SD basis vector, f is the FD basis vector, and c is the linear combination coefficients to combine the SD and FD bases.

As shown in the formula above, with two polarizations, a particular SD and a particular FD basis form matrix G _k. with size P×N ₃ across the N ₃ subbands. Since there are L SD bases and M FD bases, fhe final precoder is actually a linear combination of 2LM matrices (i.e., G ₀, ..., G _k) .

In some wireless communication systems (e.g., an NR Release-16 system) , in a port-selection codebook, a CSI-RS port on N ₃ FD units (e.g., an FD unit may be a resource block (RB) or a sub-band) is precoded with a specific SD basis and a specific FD basis. Here, each CSI-RS port is associated with the same SD and FD basis across all sub-bands, but is rotated on each sub-band. Each of the CSI-RS ports uses a different SD basis and/or FD basis as the other CSI-RS ports. In some examples, the base station can obtain the spatial reciprocity and delay reciprocity via the sounding reference signal sent from the UE, and then perform the precoding using the SD and/or FD basis derived based on the obtained spatial/delay reciprocity.

The SD and FD bases are emulated by the base station and, thus, can be transparent to the UE. In this case, the UE may not know or be configured with the SD and FD bases. Instead, the UE can perform CSI-RS port selection, form the precoding matrix indicator (PMI) , and compute linear combination coefficients for the selected CSI-RS. For example, the UE can select K ₀ CSI-RS ports of a set of P CSI-RS ports, where K ₀ may be configured by the base station. The base station may emulate the P CSI-RS ports out of N ₁N ₂N ₃ candidate basis. The UE can do a covariance wideband computation to derive the coefficients for the selected CSI-RS ports. The UE can then report K ₀ wideband coefficients associated with the K ₀ selected CSI-RS ports. Thus, as compared to digital feedforward CSI feedback, the CSI reporting overhead and complexity is reduced. Also, there may be increased flexibility with the CSI-RS emulation. In some cases, the FD unit granularity may be finer (e.g., RB-level) .

According to the above-described analog feedforward framework, the base station precodes CSI-RS with both an SD basis and an FD basis. However, this requires full and accurate channel information in order to estimate the spatial beam and delay path domain information, which may not be readily achievable (e.g., in a frequency division duplex (FDD) scenario or in a time division duplex (TDD) scenario without perfect reciprocity) . Further, the number of CSI-RS ports is increased with the increasing of the SD/FD precoded basis (e.g., 32 CSI-RS ports are needed if a total number of SD/FD basis combinations is 32) . Notably, these FD precoded CSI-RS ports are correlated at least for the same SD precoder. That is, a relative phase offset is generated due to the application of the different frequency domain bases, as illustrated in Fig. 3.

Some aspects described herein provide techniques and apparatuses for enhancements for analog feedforward CSI-RS. In some aspects, the enhancements include multiplexing (also referred to herein as bundling) SD/FD precoded CSI-RS ports. In some aspects, bundling the SD/FD precoded CSI-RS ports may enable improved CSI-RS channel estimation accuracy and/or reduce CSI-RS overhead. That is, in some aspects, CSI-RS ports may be reduced (e.g., since CSI-RS ports under one SD basis are FD multiplexed) and/or CSI-RS port channel estimation accuracy may be improved by the bundling of the SD/FD precoded CSI-RS ports. Additional details are provided below.

Figs. 4A-4C are diagrams associated with enhancements for analog feedforward CSI-RS, in accordance with various aspects of the present disclosure. Fig. 4A illustrates example 400 of operations of a base station (e.g., base station 110) and a UE (e.g., UE 120) in association with providing enhancements for analog feedforward CSI-RS.

As shown in Fig. 4A by reference 405, the base station may provide, and the UE may receive, a CSI-RS configuration including CSI-RS bundling information. In some aspects, the CSI-RS bundling information may be designed such that each CSI-RS port in a given group of bundled CSI-RS ports is precoded using a same SD basis and such that each CSI-RS port in the given group of bundled CSI-RS ports is precoded with a different FD basis.

In some aspects, the CSI-RS bundling information may identify one or more parameters associated with bundling CSI-RS ports. For example, the CSI-RS bundling information may include information that identifies a number of groups of bundled CSI- RS ports. That is, the CSI-RS bundling information may indicate a number of groups (e.g., one group, two groups, and so on) , where each group includes one or more CSI-RS ports. As another example, the CSI-RS bundling information may include information that identifies a number of CSI-RS ports in a given group of bundled CSI-RS ports. In some aspects, the identified number of ports may be associated with one or more groups of the groups of bundled CSI-RS ports (i.e., the identified number of ports may indicate the number of CSI-RS ports in multiple groups) . As another example, the CSI-RS bundling information may include information that identifies one or more particular CSI-RS ports included in a given group of bundled CSI-RS ports. That is, the CSI-RS bundling information may include information that identifies one or more particular ports (e.g., on an individual basis, based on a range of port numbers, and/or the like) included in a given group of bundled CSI-RS ports.

In some aspects, the number of groups of bundled CSI-RS ports, the number of ports in the group of bundled CSI-RS ports, and/or the particular CSI-RS ports included in the group of bundled CSI-RS ports may be indicated via, for example, values of one or more bits (e.g., in log ₂ (32) = 5 bits) included in the CSI-RS configuration, or a bitmap included in the CSI-RS configuration (e.g., a bitmap of 32 bits) .

In some aspects, the CSI-RS bundling information may identify one or more parameters associated with an FD basis candidate set for each group of bundled CSI-RS. For example, the CSI-RS bundling information may include information that identifies one or more FD basis candidate sets associated with the one or more groups of bundled CSI-RS ports. In some aspects, the FD basis candidate set may be a discrete Fourier transform (DFT) matrix, where a size of the DFT matrix is associated with a number of sub-bands of the CSI-RS, a number of resource blocks of the CSI-RS, or a CSI reporting configuration. In some aspects, the FD basis candidate set may be the same FD basis set as defined in Release-16 Type-II CSI (i.e., an N ₃ sized DFT matrix) .

In some aspects, to improve the performance of channel estimation, the base station may determine the CSI-RS bundling information such that CSI-RS ports in a given group of bundled CSI-RS ports are mapped to adjacent frequency and/or time resources. For example, the base station may determine the CSI-RS bundling information such that a same code division multiplexing (CDM) group (or FD adjacent CDM groups) are used for CSI-RS ports in the given group of bundled CSI-RS ports. Alternatively, in some aspects, the base station may determine the CSI-RS bundling information such that CSI-RS ports in a given group of bundled CSI-RS ports are mapped to non-adjacent frequency and/or time resources.

In some aspects, the CSI-RS bundling information may further include information that identifies an FD multiplexing level. The FD multiplexing level may be associated with FD multiplexing, code division multiplexing, or time division multiplexing within the group of bundled CSI-RS ports. In some aspects, multiplexing within a given group of bundled CSI-RS may further improve channel estimation performance and/or further reduce CSI-RS pilot density.

As shown by reference 410, the base station may transmit the CSI-RS based at least in part on the CSI-RS bundling information. In some aspects, the CSI-RS may be transmitted such that each CSI-RS port in a given group of bundled CSI-RS ports is precoded using a same SD basis and such that each CSI-RS port in the given group of bundled CSI-RS ports is precoded with a different FD basis, as described above. As further indicated by reference 410, the UE may receive the CSI-RS on the groups of bundled CSI-RS ports.

As shown by reference 415, the UE, after receiving the CSI-RS configuration and upon receiving the CSI-RS may recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS. For example, the UE may estimate an FD basis index based at least in part on the CSI-RS configuration and the CSI-RS. Next, the UE may perform a wideband channel estimation based at least in part on the estimated FD basis index. The UE may then recover the channel based at least in part on the estimated FD basis index and an output of the wideband channel estimation.

Fig. 4B is a diagram illustrating an example CSI-RS port bundling as described above in connection with Fig. 4A. In Fig. 4B, four CSI-RS ports are divided into two groups (Group 1 and Group 2) . As shown in Fig. 4B, a first SD basis (b ₀) is applied to the CSI-RS ports in Group 1, while a second SD basis (b ₁) is applied to the CSI-RS ports in Group 2. Thus, in this example, each CSI-RS port in a given group of bundled CSI-RS ports is precoded using a same SD basis. As further shown in Fig. 4B, within a given group of bundled CSI-RS ports, each CSI-RS port is precoded with a different FD basis.

Fig. 4C is a diagram illustrating an example CSI-RS port bundling using an FD multiplexing level, as described above in connection with Fig. 4A. In Fig. 4C, eight CSI-RS ports are divided into two groups (Group 1 and Group 2) , and the FD multiplexing level is 2. As shown in Fig. 4C, a first SD basis (b ₀) is applied to the CSI-RS ports in Group 1, while a second SD basis (b ₁) is applied to the CSI-RS ports in Group 2. Thus, in this example, each CSI-RS port in a given group of bundled CSI-RS ports is precoded using a same SD basis. As further shown in Fig. 4C, within a given group of bundled CSI-RS ports, each CSI-RS port is precoded with a different FD basis. As shown in Fig. 4C and based at least in part on the FD multiplexing level, for Group 1, the first and second CSI-RS ports are code division multiplexed and mapped to a first RB, and the third and fourth CSI-RS ports are code division multiplexed and mapped to a second RB.

As indicated above, Figs. 4A-4C are provided as examples. Other examples may differ from what is described with respect to Figs. 4A-4C.

Fig. 5 is a diagram illustrating an example process 500 performed, for example, by a base station, in accordance with various aspects of the present disclosure. Example process 500 is an example where the base station (e.g., base station 110 and/or the like) performs operations associated with enhancements for analog feedforward CSI-RS.

As shown in Fig. 5, in some aspects, process 500 may include providing a CSI-RS configuration including CSI-RS bundling information (block 510) . For example, the base station (e.g., using transmit processor 220, controller/processor 240, memory 242, and/or the like) may provide a CSI-RS configuration including CSI-RS bundling information, as described above. In some aspects, the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports

As further shown in Fig. 5, in some aspects, process 500 may include transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information (block 520) . For example, the base station (e.g., using transmit processor 220, controller/processor 240, memory 242, and/or the like) may transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information, as described above.

Process 500 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, each CSI-RS port in the group of bundled CSI-RS ports is precoded using a same SD basis.

In a second aspect, alone or in combination with the first aspect, each CSI-RS port in the group of bundled CSI-RS ports is precoded with a different FD basis.

In a third aspect, alone or in combination with one or more of the first and second aspects, the number of groups of bundled CSI-RS ports, the number of ports in the group of bundled CSI-RS ports, or the particular CSI-RS ports included in the group of bundled CSI-RS ports is indicated via at least one of: values of one or more bits included in the CSI-RS configuration, or a bitmap included in the CSI-RS configuration.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the FD basis candidate set is a discrete Fourier transform (DFT) matrix, wherein a size of the DFT matrix is associated with at least one of: a number of sub-bands of the CSI-RS, a number of resource blocks of the CSI-RS, or a CSI reporting configuration.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, CSI-RS ports in the group of bundled CSI-RS ports are mapped to adjacent frequency and/or time resources.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, a same code division multiplexing (CDM) group or FD adjacent CDM groups are used for the CSI-RS ports in the group of bundled CSI-RS ports.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, CSI-RS ports in the group of bundled CSI-RS ports are mapped to non-adjacent frequency and/or time resources.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the CSI-RS bundling information identifies an FD multiplexing level associated with FD multiplexing, code division multiplexing, or time division multiplexing within the group of bundled CSI-RS ports, wherein the CSI-RS transmitted on the group of bundled CSI-RS ports is multiplexed based at least in part on the FD multiplexing level.

Although Fig. 5 shows example blocks of process 500, in some aspects, process 500 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 5. Additionally, or alternatively, two or more of the blocks of process 500 may be performed in parallel.

Fig. 6 is a diagram illustrating an example process 600 performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process 600 is an example where the UE (e.g., UE 120 and/or the like) performs operations associated with enhancements for analog feedforward CSI-RS.

As shown in Fig. 6, in some aspects, process 600 may include receiving a CSI-RS configuration including CSI-RS bundling information (block 610) . For example, the UE (e.g., using receive processor 258, controller/processor 280, memory 282, and/or the like) may receive a CSI-RS configuration including CSI-RS bundling information, as described above. In some aspects, the CSI-RS bundling information identifies at least one of: a number of groups of bundled CSI-RS ports, a number of ports in a group of bundled CSI-RS ports, particular CSI-RS ports included in the group of bundled CSI-RS ports, or an FD basis candidate set associated with the group of bundled CSI-RS ports.

As further shown in Fig. 6, in some aspects, process 600 may include receiving a CSI-RS on the group of bundled CSI-RS ports (block 620) . For example, the UE (e.g., using receive processor 258, controller/processor 280, memory 282, and/or the like) may receive a CSI-RS on the group of bundled CSI-RS ports, as described above.

As further shown in Fig. 6, in some aspects, process 600 may include recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS (block 630) . For example, the UE (e.g., using receive processor 258, controller/processor 280, memory 282, and/or the like) may recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS, as described above.

Process 600 may include additional aspects, such as any single aspect or any combination of aspects described below and/or in connection with one or more other processes described elsewhere herein.

In a first aspect, recovering the channel associated with the CSI-RS comprises: estimating an FD basis index based at least in part on the CSI-RS configuration and the CSI-RS; performing a wideband channel estimation based at least in part on the estimated FD basis index; and recovering the channel based at least in part on the estimated FD basis index and an output of the wideband channel estimation.

In a second aspect, alone or in combination with the first aspect, each CSI-RS port in the group of bundled CSI-RS ports is precoded using a same SD basis.

In a third aspect, alone or in combination with one or more of the first and second aspects, each CSI-RS port in the group of bundled CSI-RS ports is precoded with a different FD basis.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, the number of groups of bundled CSI-RS ports, the number of ports in the group of bundled CSI-RS ports, or the particular CSI-RS ports included in the group of bundled CSI-RS ports is indicated via at least one of: values of one or more bits included in the CSI-RS configuration, or a bitmap included in the CSI-RS configuration.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the FD basis candidate set is a DFT matrix, wherein a size of the DFT matrix is associated with at least one of: a number of sub-bands of the CSI-RS, a number of resource blocks of the CSI-RS, or a CSI reporting configuration.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, CSI-RS ports in the group of bundled CSI-RS ports are mapped to adjacent frequency and/or time resources.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, a same CDM group or FD adjacent CDM groups are used for the CSI-RS ports in the group of bundled CSI-RS ports.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, CSI-RS ports in the group of bundled CSI-RS ports are mapped to non-adjacent frequency and/or time resources.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, the CSI-RS bundling information identifies an FD multiplexing level associated with FD multiplexing, code division multiplexing, or time division multiplexing within the group of bundled CSI-RS ports, wherein the CSI-RS transmitted on the group of bundled CSI-RS ports is multiplexed based at least in part on the FD multiplexing level.

Although Fig. 6 shows example blocks of process 600, in some aspects, process 600 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 6. Additionally, or alternatively, two or more of the blocks of process 600 may be performed in parallel.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the aspects to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the aspects.

As used herein, the term “component” is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. As used herein, a processor is implemented in hardware, firmware, or a combination of hardware and software.

Some aspects are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.

It will be apparent that systems and/or methods described herein may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the aspects. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code-it being understood that software and hardware can be designed to implement the systems and/or methods based, at least in part, on the description herein.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of various aspects. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of various aspects includes each dependent claim in combination with every other claim in the claim set. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more. ” Furthermore, as used herein, the terms “set” and “group” are intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and/or the like) , and may be used interchangeably with “one or more. ” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has, ” “have, ” “having, ” and/or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

Claims

A method of wireless communication performed by a base station, comprising:

providing a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports; and

transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.
The method of claim 1, wherein each CSI-RS port in the group of bundled CSI-RS ports is precoded using a same spatial domain (SD) basis.
The method of claim 1, wherein each CSI-RS port in the group of bundled CSI-RS ports is precoded with a different FD basis.
The method of claim 1, wherein the number of groups of bundled CSI-RS ports, the number of ports in the group of bundled CSI-RS ports, or the particular CSI-RS ports included in the group of bundled CSI-RS ports is indicated via at least one of:

values of one or more bits included in the CSI-RS configuration, or

a bitmap included in the CSI-RS configuration.
The method of claim 1, wherein the FD basis candidate set is a discrete Fourier transform (DFT) matrix,

wherein a size of the DFT matrix is associated with at least one of:

a number of sub-bands of the CSI-RS,

a number of resource blocks of the CSI-RS, or

a CSI reporting configuration.
The method of claim 1, wherein CSI-RS ports in the group of bundled CSI-RS ports are mapped to adjacent frequency and/or time resources.
The method of claim 6, wherein a same code division multiplexing (CDM) group or FD adjacent CDM groups are used for the CSI-RS ports in the group of bundled CSI-RS ports.
The method of claim 1, wherein CSI-RS ports in the group of bundled CSI-RS ports are mapped to non-adjacent frequency and/or time resources.
The method of claim 1, wherein the CSI-RS bundling information identifies an FD multiplexing level associated with FD multiplexing, code division multiplexing, or time division multiplexing within the group of bundled CSI-RS ports,

wherein the CSI-RS transmitted on the group of bundled CSI-RS ports is multiplexed based at least in part on the FD multiplexing level.
A method of wireless communication performed by a user equipment (UE) , comprising:

receiving a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports;

receiving a CSI-RS on the group of bundled CSI-RS ports; and

recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.
The method of claim 10, wherein recovering the channel associated with the CSI-RS comprises:

estimating an FD basis index based at least in part on the CSI-RS configuration and the CSI-RS;

performing a wideband channel estimation based at least in part on the estimated FD basis index; and

recovering the channel based at least in part on the estimated FD basis index and an output of the wideband channel estimation.
The method of claim 10, wherein each CSI-RS port in the group of bundled CSI-RS ports is precoded using a same spatial domain (SD) basis.
The method of claim 10, wherein each CSI-RS port in the group of bundled CSI-RS ports is precoded with a different FD basis.
The method of claim 10, wherein the number of groups of bundled CSI-RS ports, the number of ports in the group of bundled CSI-RS ports, or the particular CSI-RS ports included in the group of bundled CSI-RS ports is indicated via at least one of:

values of one or more bits included in the CSI-RS configuration, or

a bitmap included in the CSI-RS configuration.
The method of claim 10, wherein the FD basis candidate set is a discrete Fourier transform (DFT) matrix,

wherein a size of the DFT matrix is associated with at least one of:

a number of sub-bands of the CSI-RS,

a number of resource blocks of the CSI-RS, or

a CSI reporting configuration.
The method of claim 10, wherein CSI-RS ports in the group of bundled CSI-RS ports are mapped to adjacent frequency and/or time resources.
The method of claim 16, wherein a same code division multiplexing (CDM) group or FD adjacent CDM groups are used for the CSI-RS ports in the group of bundled CSI-RS ports.
The method of claim 10, wherein CSI-RS ports in the group of bundled CSI-RS ports are mapped to non-adjacent frequency and/or time resources.
The method of claim 10, wherein the CSI-RS bundling information identifies an FD multiplexing level associated with FD multiplexing, code division multiplexing, or time division multiplexing within the group of bundled CSI-RS ports,

wherein the CSI-RS received on the group of bundled CSI-RS ports is multiplexed based at least in part on the FD multiplexing level.
A base station for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

provide a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports; and

transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.
A user equipment (UE) for wireless communication, comprising:

a memory; and

one or more processors operatively coupled to the memory, the memory and the one or more processors configured to:

receive a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports;

receive a CSI-RS on the group of bundled CSI-RS ports; and

recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a base station, cause the one or more processors to:

provide a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports; and

transmit a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.
A non-transitory computer-readable medium storing one or more instructions for wireless communication, the one or more instructions comprising:

one or more instructions that, when executed by one or more processors of a user equipment (UE) , cause the one or more processors to:

receive a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports;

receive a CSI-RS on the group of bundled CSI-RS ports; and

recover a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.
An apparatus for wireless communication, comprising:

means for providing a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports; and

means for transmitting a CSI-RS on the group of bundled CSI-RS ports based at least in part on the CSI-RS bundling information.
An apparatus for wireless communication, comprising:

means for receiving a channel state information reference signal (CSI-RS) configuration including CSI-RS bundling information,

wherein the CSI-RS bundling information identifies at least one of:

a number of groups of bundled CSI-RS ports,

a number of ports in a group of bundled CSI-RS ports,

particular CSI-RS ports included in the group of bundled CSI-RS ports, or

a frequency domain (FD) basis candidate set associated with the group of bundled CSI-RS ports;

means for receiving a CSI-RS on the group of bundled CSI-RS ports; and

means for recovering a channel, associated with the CSI-RS, based at least in part on the CSI-RS configuration and the CSI-RS.