Port Selection for Channel State Feedback with Analog Feedforward

Abstract

Certain aspects of the present disclosure provide techniques for port selection for channel state feedback with analog feedforward. A method that can be performed by a user equipment (UE) includes: selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the UE to report CSI. The port selection includes: selecting any CSI-RS port from the plurality of CSI-RS ports or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The UE determines a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports. The UE calculates at least a wideband linear combination coefficient for the selected CSI-RS port. The UE provides the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a base station (BS) in a CSI report.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of and priority to PCT International Application No. PCT / CN2019 / 110286, filed on October 10, 2019, and the entire text of that patent application is hereby incorporated by reference herein. Technical Field

[0003] Various aspects of the present disclosure relate to wireless communications and, more particularly, to techniques for port selection for channel state feedback with analog feedforward. Background Art

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcasts. These 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, etc.). Examples of such multiple-access systems include the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, the Advanced LTE (LTE-A) system, the Code Division Multiple Access (CDMA) system, the Time Division Multiple Access (TDMA) system, the Frequency Division Multiple Access (FDMA) system, the Orthogonal Frequency Division Multiple Access (OFDMA) system, the Single Carrier Frequency Division Multiple Access (SC-FDMA) system, and the Time Division Synchronous Code Division Multiple Access (TD-SCDMA) system.

[0005] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard released by 3GPP. NR is designed to better integrate with other open standards by improving spectrum efficiency, reducing costs, improving services, utilizing new spectrum, and using OFDMA with cyclic prefix (CP) on the downlink (DL) and uplink (UL), thereby better supporting mobile broadband Internet access. To this end, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0006] However, as demand for mobile broadband access continues to grow, there is a need for further improvements to NR and LTE technologies. Preferably, these improvements should also apply to other multiple access technologies and the telecommunication standards that employ them. Summary of the Invention

[0007] The systems, methods, and devices of the present disclosure each have several aspects, no single aspect of which is solely responsible for its desired properties. Without limiting the scope of the present disclosure as expressed by the claims that follow, some features will now be briefly discussed. After considering this discussion, and particularly after reading the section entitled "Detailed Description," those skilled in the art will understand how the features of the present disclosure, including channel state feedback port selection with analog feedback, provide advantages.

[0008] One innovative aspect of the subject matter described in the present disclosure may be implemented in a method for wireless communication performed by a user equipment (UE). The method generally includes: selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the UE to report CSI. The port selection includes: selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The method generally includes: determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports. The method generally includes: at least calculating a broadband linear combination coefficient for the selected CSI-RS port. The method generally includes: providing the selected one or more CSI-RS ports and the calculated broadband linear combination coefficient to a base station (BS) in a CSI report.

[0009] One innovative aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication performed by a base station. The method generally includes sending a CSI request to a user equipment terminal (UE) for a PMI formed by a linear combination of a plurality of CSI-RS ports selected by the UE. The port selection includes selecting any CSI-RS port from the plurality of CSI-RS ports or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The method generally includes receiving a CSI report from the UE including at least a port selection and a wideband linear combination coefficient.

[0010] One innovative aspect of the subject matter described in the present disclosure may be implemented in an apparatus for wireless communication. The apparatus may include a memory and at least one processor coupled to the memory. The at least one processor coupled to the memory may be configured to select one or more CSI-RS ports from a plurality of CSI-RS ports for the apparatus to report CSI. The port selection may include selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The at least one processor coupled to the memory may be configured to determine a PMI formed by a linear combination of the one or more selected CSI-RS ports. The at least one processor coupled to the memory may be configured to at least calculate a wideband linear combination coefficient for the selected CSI-RS port. The at least one processor coupled to the memory may be configured to provide the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a BS in a CSI report.

[0011] One innovative aspect of the subject matter described in the present disclosure may be implemented in an apparatus for wireless communication. The apparatus may include a memory and at least one processor coupled to the memory. The at least one processor coupled to the memory may be configured to: send a CSI request to a UE for a PMI formed by a linear combination of multiple CSI-RS ports selected by the UE. The port selection may include: selecting any CSI-RS port from the multiple CSI-RS ports; or selecting a CSI-RS port based on a grouping of the multiple CSI-RS ports. The at least one processor coupled to the memory may be configured to: receive a CSI report from the UE that includes at least a port selection and a wideband linear combination coefficient.

[0012] One innovative aspect of the subject matter described in the present disclosure may be implemented in an apparatus for wireless communication. The apparatus may include: a unit for selecting one or more CSI-RS ports from a plurality of CSI-RS ports for the apparatus to report CSI. The port selection may include: selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The apparatus may include: a unit for determining a PMI formed by a linear combination of the one or more selected CSI-RS ports. The apparatus may include: a unit for calculating at least a wideband linear combination coefficient for the selected CSI-RS port. The apparatus may include: a unit for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a BS in a CSI report.

[0013] One innovative aspect of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus may include: means for sending a CSI request to a UE for a PMI formed by a linear combination of a plurality of CSI-RS ports selected by the UE. The port selection may include: selecting any CSI-RS port from the plurality of CSI-RS ports; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. The apparatus may include means for receiving a CSI report from the UE including at least the port selection and a wideband linear combination coefficient.

[0014] One innovative aspect of the subject matter described in the present disclosure can be implemented in a computer-readable medium having computer-executable code stored thereon for wireless communication, the computer-executable code comprising: code for selecting one or more CSI-RS ports from a plurality of CSI-RS ports for a UE to report CSI, wherein the port selection comprises: selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; code for determining a PMI formed by a linear combination of the one or more selected CSI-RS ports; code for calculating at least a wideband linear combination coefficient for the selected CSI-RS ports; and code for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a BS in a CSI report.

[0015] One innovative aspect of the subject matter described in the present disclosure can be implemented in a computer-readable medium having computer-executable code stored thereon for wireless communication, the computer-executable code comprising: code for sending a CSI request to a UE for a PMI formed by a linear combination of a plurality of CSI-RS ports selected by the UE, wherein the port selection comprises selecting any CSI-RS port from the plurality of CSI-RS ports or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; and code for receiving a CSI report from the UE including at least the port selection and a wideband linear combination coefficient.

[0016] To accomplish the foregoing and related ends, one or more aspects include the features hereinafter fully described and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative features of one or more aspects. However, these features are indicative of only some of the various ways in which the principles of the various aspects may be employed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more particular description, briefly summarized above, may be had by reference to some of the various aspects shown in the accompanying drawings so that the above-mentioned features of the present disclosure may be understood in detail. It should be noted, however, that the drawings illustrate only certain typical aspects of the present disclosure and are therefore not to be considered limiting of its scope, as the description may admit to other equally effective aspects.

[0018] Figure 1 is a block diagram conceptually illustrating an example telecommunications system in accordance with certain aspects of the present disclosure.

[0019] Figure 2 is a block diagram conceptually illustrating a design of an example of a base station (BS) and a user equipment (UE), in accordance with certain aspects of the present disclosure.

[0020] Figure 3 is an example frame format for certain wireless communication systems (e.g., New Radio (NR)) in accordance with certain aspects of the present disclosure.

[0021] Figure 4 Precoders across different channel state information reference signal (CSI-RS) ports and frequency domain (FD) units are shown in accordance with aspects of the present disclosure.

[0022] Figure 5 Precoders for CSI-RS ports organized in groups according to aspects of the present disclosure are shown.

[0023] Figure 6A Precoders for CSI-RS ports organized with CSI-RS resources are shown in accordance with aspects of the present disclosure.

[0024] Figure 6B Precoders for CSI-RS ports organized with CSI-RS resources are shown in accordance with aspects of the present disclosure.

[0025] Figure 7 is a flow diagram illustrating example operations by a UE for wireless communications in accordance with certain aspects of the present disclosure.

[0026] Figure 8 is a flow diagram illustrating example operations by a BS for wireless communications in accordance with certain aspects of the present disclosure.

[0027] Figure 9 A communication device according to aspects of the present disclosure is shown that may include various components configured to perform operations of the techniques disclosed herein.

[0028] Figure 10A communication device according to aspects of the present disclosure is shown that may include various components configured to perform operations of the techniques disclosed herein.

[0029] Figure 11 Precoders across different CSI-RS ports and FD units are shown in accordance with aspects of the present disclosure.

[0030] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation. DETAILED DESCRIPTION

[0031] Aspects of the present disclosure provide devices, methods, processing systems, and computer-readable media for port selection for channel state feedback with analog feedforward.

[0032] The following description provides examples of port selection for channel state feedback with analog feedforward, and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of the elements discussed without departing from the scope of this disclosure. Various examples may omit, replace, or add various processes or components as appropriate. For example, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, features described with respect to some examples may be combined in some other examples. For example, a device may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of this disclosure is intended to cover such devices or methods practiced using other structures, functions, or structures and functions in addition to or different from 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 the claims. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects.

[0033] In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a specific radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, air interface, etc. A frequency may also be referred to as a carrier, subcarrier, frequency channel, tone, subband, etc. Each frequency may support a single RAT in a given geographic area to avoid interference between wireless networks of different RATs.

[0034] The techniques described herein can be used for various wireless networks and radio technologies. For clarity, although various aspects may be described herein using terminology typically associated with 3G, 4G, and / or new radio (e.g., 5G NR) wireless technologies, various aspects of the present disclosure can be applied to communication systems based on other generations.

[0035] NR access (e.g., 5G technology) can support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or higher), millimeter wave (mmW) targeting high carrier frequency (e.g., 25 GHz or higher), massive machine type communication MTC (mMTC) targeting non-backward compatible MTC technology, and / or mission critical targeting ultra-reliable low latency communication (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTIs) to meet corresponding quality of service (QoS) requirements. In addition, these services can coexist in the same subframe.

[0036] NR supports beamforming and dynamically configurable beam directions. MIMO transmission with precoding is also supported. DL MIMO configurations can support up to 8 transmit antennas, with multi-layer DL transmissions of up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE are also supported. Multiple cell aggregation with up to 8 serving cells is also supported.

[0037] Figure 1 1 shows an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network). Figure 1 As shown in FIG, the wireless communication network 100 may communicate with a core network 132. The core network 132 may communicate with one or more base stations (BSs) 110a-z (each also referred to herein individually as a BS 110 or collectively as BS 110) and / or user equipments (UEs) 120a-y (each also referred to herein individually as a UE 120 or collectively as UE 120) in the wireless communication network 100 via one or more interfaces.

[0038] BS 110 may provide communication coverage for a particular geographic area (sometimes referred to as a "cell"), which may be fixed or may move depending on the location of mobile BS 110. In some examples, BS 110 may interconnect with each other and / or with one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., direct physical connections, wireless connections, virtual networks, etc.) using any suitable transport network. Figure 1 In the illustrated example, BSs 110a, 110b, and 110c may be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x may be a pico BS for pico cell 102x. BSs 110y and 110z may be femto BSs for femto cells 102y and 102z, respectively. A BS may support one or more cells. BS 110 communicates with user equipment (UEs) 120a-y (each also referred to herein individually as a UE 120 or collectively as UEs 120) in wireless communication network 100. UEs 120 (e.g., 120x, 120y, etc.) may be dispersed throughout wireless communication network 100, and each UE 120 may be stationary or mobile.

[0039] According to certain aspects, BS 110 and UE 120 may be configured for port selection for channel state feedback with analog feedforward. Figure 1 As shown in FIG, BS 110a includes a CSI-RS manager 112. According to aspects of the present disclosure, the CSI-RS manager 112 may be configured to precode a plurality of CSI-RS ports by applying a different precoder at each of the CSI-RS ports, and to apply the same precoder across all frequency domain (FD) units for each CSI-RS port, and to transmit the CSI-RS to the UE via the precoded CSI-RS ports. According to aspects of the present disclosure, the CSI-RS manager 112 may be configured to transmit a request for a PMI to the UE 120a and to receive a CSI report from the UE. Figure 1 As shown in FIG, UE 120a includes a CSI manager 122. According to aspects of the present disclosure, the CSI manager 122 can be configured to: select one or more CSI-RS ports from a plurality of CSI-RS ports for UE CSI reporting using polarization-specific or polarization-common port selection based on grouping of the plurality of CSI-RS ports; determine a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; calculate wideband linear combination coefficients for the selected CSI-RS ports; and provide the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to a BS in a CSI report.

[0040] The wireless communication network 100 may also include a relay station (e.g., relay station 110r) (also referred to as a repeater, etc.) that receives transmissions of data and / or other information from an upstream station (e.g., BS 110a or UE 120r) and sends transmissions of data and / or other information to a downstream station (e.g., UE 120 or BS 110), or relays transmissions between UEs 120 to facilitate communication between devices.

[0041] The network controller 130 may be coupled to a set of BSs 110 and provide coordination and control of the BSs 110. In various aspects, the network controller 130 may communicate with a core network 132 (e.g., a 5G core network (5GC)), which provides various network functions such as access and mobility management, session management, user plane functions, policy control functions, authentication server functions, unified data management, application functions, network exposure functions, network storage functions, network slice selection functions, etc.

[0042] Figure 2 1 shows a BS 110a and a UE 120a (eg, Figure 1 Example components of the wireless communication network 100 of FIG.

[0043] At BS 110a, transmit processor 220 may receive data from data source 212 and control information from controller / processor 240. Control information may be used for a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), a physical downlink control channel (PDCCH), a group common PDCCH (GC PDCCH), etc. Data may be used for a physical downlink shared channel (PDSCH), etc. A medium access control (MAC) control element (MAC-CE) is a MAC layer communication structure that may be used to exchange control commands between wireless nodes. For example, a base station may send a MAC CE to a user equipment (UE) to place the UE in discontinuous reception (DRX) mode to reduce the UE's power consumption. A MAC-CE may be carried in a shared channel (e.g., a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel). A MAC-CE may also be used to convey information that facilitates communication, such as information about buffer status and available power headroom.

[0044] The processor 220 can process (e.g., encode and symbol map) data and control information, respectively, to obtain data symbols and control symbols. The transmit processor 220 can also generate reference symbols, such as for the primary synchronization signal (PSS), the secondary synchronization signal (SSS), and the CSI-RS. The transmit (TX) multiple-input multiple-output (MIMO) processor 230 can perform spatial processing (e.g., precoding) on the data symbols, control symbols, and / or reference symbols (if applicable), and can provide output symbol streams to the modulators (MODs) 232a-232t in the transceiver. Each modulator can process a corresponding output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator can further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The downlink signals from the modulators 232a-232t in the transceiver can be transmitted via antennas 234a-234t, respectively.

[0045] At UE 120a, antennas 252a-252r can receive downlink signals from BS 110a and can provide received signals to demodulators (DEMODs) 254a-254r, respectively, in the transceiver. Each demodulator can condition (e.g., filter, amplify, downconvert, and digitize) a corresponding received signal to obtain input samples. Each demodulator can further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 256 can obtain received symbols from all demodulators 254a-254r in the transceiver, perform MIMO detection on the received symbols (if applicable), and provide detected symbols. A receive processor 258 can process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 120a to a data sink 260, and provide decoded control information to a controller / processor 280.

[0046] On the uplink, at UE 120a, a transmit processor 264 may receive and process data from a data source 262 (e.g., for a physical uplink shared channel (PUSCH)) and control information from a controller / processor 280 (e.g., for a physical uplink control channel (PUCCH)). The transmit processor 264 may also generate reference symbols for reference signals (e.g., for a sounding reference signal (SRS)). The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 (if applicable), further processed by demodulators 254a-254r in the transceiver (e.g., for SC-FDM, etc.), and transmitted to BS 110a. At BS 110a, the uplink signal from UE 120a may be received by an antenna, processed by a modulator 232, detected by a MIMO detector 236 (if applicable), and further processed by a receive processor 238 to obtain decoded data and control information transmitted by UE 120a. Receive processor 238 may provide decoded data to a data sink 239 and decoded control information to controller / processor 240 .

[0047] Memories 242 and 282 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 244 may schedule UEs for data transmission on the downlink and / or uplink.

[0048] The antennas 252, processors 266, 258, 264, and / or controller / processor 280 of the UE 120a and the antennas 234, processors 220, 230, 238, and / or controller / processor 240 of the BS 110a may be used to perform the various techniques and methods described herein. Figure 2 As shown in FIG, the controller / processor 240 of the BS 110a has a CSI-RS manager 241, which can be configured to precode multiple CSI-RS ports by applying a different precoder at each of the CSI-RS ports, apply the same precoder across all FD units for each CSI-RS port, and transmit the CSI-RS to the UE via the precoded CSI-RS ports. According to various aspects described herein, Figure 2As shown in FIG, the controller / processor 280 of the UE 120a has a CSI manager 281. The CSI manager 281 can be configured to: select one or more CSI-RS ports from a plurality of CSI-RS ports for the UE to report CSI using polarization-specific or polarization-common port selection based on grouping of the plurality of CSI-RS ports; determine a PMI formed by a linear combination of the one or more selected CSI-RS ports; calculate a wideband linear combination coefficient for the selected CSI-RS ports; and provide the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to the BS in a CSI report. Although shown at the controller / processor, other components of the UE 120a and the BS 110a can be used to perform the operations described herein.

[0049] NR can utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on both the uplink and downlink. NR can support half-duplex operation using time division multiplexing (TDD). OFDM and single-carrier frequency division multiplexing (SC-FDM) can divide the system bandwidth into multiple orthogonal subcarriers, which are often referred to as tones, bins, etc. Each subcarrier can be modulated with data. Modulation symbols can be sent in the frequency domain using OFDM, and the modulated signal can be sent in the time domain using SC-FDM. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers can depend on the system bandwidth. The minimum resource allocation, called a resource block (RB), can be 12 consecutive subcarriers. The system bandwidth can also be divided into subbands. For example, a subband can cover multiple RBs. NR can support a basic subcarrier spacing (SCS) of 15 kHz, and other SCSs can be defined with respect to the basic SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.).

[0050] Figure 33 is a diagram illustrating an example of a frame format 300 for NR. The transmission timeline for each of the downlink and uplink can be divided into units of radio frames. Each radio frame can have a predetermined duration (e.g., 10 ms) and can be divided into 10 subframes with indices 0 to 9, each subframe being 1 ms. Each subframe can include a variable number of slots (e.g., 1, 2, 4, 8, 16, ... slots), depending on the SCS. Each slot can include a variable number of symbol periods (e.g., 7, 12, or 14 symbols), depending on the SCS. An index can be assigned to the symbol periods in each slot. The subslot structure can refer to a transmission time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols). Each symbol in a slot can be configured for a link direction (e.g., DL, UL, or flexible) for data transmission, and the link direction of each subframe can be dynamically switched. The link direction can be based on the slot format. Each slot can include DL / UL data and DL / UL control information.

[0051] In NR, synchronization signal blocks (SSBs) are transmitted. In certain aspects, SSBs may be transmitted in bursts, where each SSB in a burst corresponds to a different beam direction for UE-side beam management (e.g., including beam selection and / or beam refinement). SSBs include PSS, SSS, and two-symbol PBCH. SSBs may be transmitted in fixed slot positions, e.g., Figure 3 Symbols 0-3 shown in . PSS and SSS can be used by UE for cell search and acquisition. PSS can provide half-frame timing, and SS can provide CP length and frame timing. PSS and SSS can provide cell identification. PBCH carries some basic system information, such as downlink system bandwidth, timing information within the radio frame, SS burst set periodicity, system frame number, etc. SSBs can be organized into SS bursts to support beam scanning. Additional system information such as remaining minimum system information (RMSI), system information block (SIB), and other system information (OSI) can be sent on the physical downlink shared channel (PDSCH) in certain subframes. SSBs can be sent up to sixty-four times, for example, up to sixty-four different beam directions for millimeter waves. Multiple transmissions of SSBs are called SS burst sets. SSBs in an SS burst set can be sent in the same frequency region, while SSBs in different SS burst sets can be sent in different frequency regions.

[0052] As discussed above, various aspects of the present disclosure relate to channel state feedback with analog feedforward.The channel state feedback may include channel state information (CSI) feedback.

[0053] Example CSI Configuration

[0054] CSI can refer to the channel characteristics of a communication link. CSI can represent the combined effects of, for example, scattering, fading, and power loss with distance between the transmitter and receiver. Channel estimation using a pilot signal, such as a CSI reference signal (CSI-RS), can be performed to determine these effects on the channel. CSI can be used to adapt transmissions based on current channel conditions, which is useful for achieving reliable communication, particularly with high data rates in multi-antenna systems. CSI is typically estimated, quantized, and fed back to the transmitter at the receiver.

[0055] A UE (e.g., UE 120a) may be configured for CSI reporting by a BS (e.g., BS 110). The BS may configure the UE with a CSI reporting configuration or with multiple CSI reporting configurations. The BS may provide the CSI reporting configuration to the UE via higher layer signaling, such as radio resource control (RRC) signaling (e.g., via a CSI-ReportConfig information element (IE)).

[0056] Each CSI reporting configuration can be associated with a single downlink bandwidth part (BWP). A CSI reporting configuration can define the CSI reporting band as a subset of the subbands of the BWP. The associated DL BWP can be indicated by a higher-layer parameter (e.g., bwp-Id) in the CSI reporting configuration for channel measurement and contains parameters for one CSI reporting band, such as codebook configuration, time domain behavior, frequency granularity for CSI, measurement restriction configuration, and CSI-related quantities to be reported by the UE. Each CSI resource setting can be located in a DL BWP identified by a higher-layer parameter, and all CSI resource settings can be linked to a CSI reporting setting with the same DL BWP.

[0057] The CSI reporting configuration may configure the time and frequency resources used by the UE to report CSI. For example, the CSI reporting configuration may be associated with CSI-RS resources for channel measurement (CM), interference measurement (IM), or both. The CSI reporting configuration may configure the CSI-RS resources used for measurement (e.g., via CSI-ResourceConfig IE). The CSI-RS resources provide the UE with a configuration of CSI-RS ports or CSI-RS port groups mapped to time and frequency resources (e.g., resource elements (REs)). The CSI-RS resources may be zero power (ZP) or non-zero power (NZP) resources. At least one NZP CSI-RS resource may be configured for CM. For interference measurement, the CSI-RS may be an NZP CSI-RS or a zero power CSI-RS referred to as a CSI-IM (note that if it is an NZP CSI-RS, it is referred to as an NZP CSI-RS for interference measurement, and if it is zero power, it is referred to as a CSI-IM).

[0058] The CSI reporting configuration may configure the UE for aperiodic, periodic, or semi-persistent CSI reporting. For periodic CSI, periodic CSI-RS resources may be configured to the UE. Periodic CSI and semi-persistent CSI reporting on the physical uplink control channel (PUCCH) may be triggered via RRC or medium access control (MAC) control elements (CEs). For aperiodic and semi-persistent CSI on the physical uplink shared channel (PUSCH), the BS may signal the UE with a CSI reporting trigger that instructs the UE to send a CSI report for one or more CSI-RS resources, or configure a CSI-RS reporting trigger state (e.g., CSI-AperiodicTriggerStateList and CSI-SemiPersistentOnPUSCH-TriggerStateList). A CSI reporting trigger for aperiodic CSI and semi-persistent CSI on PUSCH may be provided via downlink control information (DCI). The CSI-RS trigger may be signaling to the UE indicating that CSI-RS is to be sent for the CSI-RS resources. The UE can report CSI feedback based on the CSI reporting configuration and CSI reporting trigger. For example, the UE can measure the channel associated with the CSI for the triggered CSI-RS resource. Based on the measurement, the UE can select a preferred CSI-RS resource. The UE reports CSI feedback for the selected CSI-RS resource.

[0059] The CSI report configuration can also configure the CSI parameters (sometimes referred to as quantities) to be reported. Codebooks can include Type I single panel, Type I multi-panel, and Type II single panel. Regardless of which codebook is used, the CSI report can include at least a channel quality indicator (CQI), a precoding matrix indicator (PMI), a CSI-RS resource indicator (CRI), and a rank indicator (RI). The structure of the PMI can vary based on the codebook. CRI, RI, and CQI can be in the first part (Part I) of the CSI report, and PMI can be in the second part (Part II) of the CSI report.

[0060] For a Type I single-plane codebook, the PMI may include the W1 matrix (e.g., a subset of beams) and the W2 matrix (e.g., the phase of the cross-polarization combination and beam selection). For a Type I multi-plane codebook, the PMI also includes the phase of the cross-plane combination compared to the Type I single-plane codebook. The BS may have multiple transmit (TX) beams. The UE may feed back the index of one or more preferred beams among the candidate beams to the BS. For example, the UE may feed back the precoding vector w for layer l:

[0061]

[0062] , where b represents an oversampled beam (eg, a discrete Fourier transform (DFT) beam) for both polarizations, and φ is co-phasing.

[0063] For a Type II codebook (e.g., as may be used for a single array), the PMI is a linear combination of beams; it has a subset of orthogonal beams to be used for the linear combination, and has a per-layer, per-polarization magnitude and phase for each beam. The preferred precoder for a layer may be a combination of a beam and associated quantization coefficients, and the UE may feed back the selected beam and coefficients to the BS.

[0064] The UE may report CSI feedback based on the CSI reporting configuration and the CSI reporting trigger. For example, the UE may measure the channel associated with the CSI for the triggered CSI-RS resource. Based on the measurement, the UE may select a preferred CSI-RS resource. The UE reports CSI feedback for the selected CSI-RS resource. The LI may be calculated conditionally on the reported CQI, PMI, RI, and CRI, the CQI may be calculated conditionally on the reported PMI, RI, and CRI, the PMI may be calculated conditionally on the reported RI and CRI, and the RI may be calculated conditionally on the reported CRI.

[0065] Example SD compressed CSI

[0066] In some systems (e.g., 5G NR Release 15), the UE may be configured to report at least the Type II precoder across the configured frequency domain (FD) units. The UE may report wideband (WB) PMI and / or subband (SB) PMI as configured.

[0067] For layer 1, its precoder across N3 FD units (also called PMI subbands) can be obtained by using the following precoder with size N t ×N3 matrix W l Given:

[0068] W l =W1×W 2,l ,

[0069] Among them, W1 and W are described in the following table 2,l :

[0070]

[0071] These two matrices can be written as:

[0072]

[0073] Among them, the SD basis is based on DFT and has index and The SD base is written as:

[0074]

[0075]

[0076] And the coefficient matrix can be written as:

[0077]

[0078] In some cases, a common (P1) value may apply to all Coefficients (or simply P1 coefficients). In this case, given 2L rows in the matrix, the P1 values are row-specific and there are 2L different possible values for these coefficients. and The description is as follows:

[0079]

[0080] More precisely, the linear combination can be expressed as:

[0081]

[0082] For the linear combination B of spatial beams, the UE can report the linear combination coefficients for each layer l and each subband i according to the precoding vector w

[0083]

[0084] The precoder matrix W is based on spatial domain (SD) compression of matrices W1 and W2 that report (for cross-polarization) linear combination coefficients across configured FD units for a selected beam (2L).

[0085] For port selection in some systems (e.g., Rel-15 NR port selection), the BS (e.g., gNB) can use The beam in is used as the precoder for CSI-RS. The precoder for the layer on the subband is given by:

[0086]

[0087] in, is a vector. In this case, the UE selects (for example) a CSI-RS port instead of selecting a beam. Therefore, when using this codebook, if the (i 11 d+i) entries are equal to 1, and the rest are 0, then this means that the (i 11 In the case of this codebook, there are P ports, where the first half of the ports are used for polarization 1 and the other half of the ports are used for polarization 2, and the same L ports are applicable to both polarizations. 11 To report the preferred candidate L ports, where the candidates are candidate L ports 0...L-1 and candidate L ports d...d+L-1. The final candidate L ports are In this case, the UE may be limited to selecting L consecutive ports (eg, port i 11 d,…i 11 d+L-1), and the maximum number of ports may be 32, which may not be enough and should be adapted to the FD basis.

[0088] Example of SD and FD compressed CSI

[0089] In some systems (e.g., Rel-16 5G NR), the UE may be configured to report frequency domain (FD) compressed precoder feedback to reduce the overhead of CSI reporting. In the case of codebook operation with FD compression, for layer 1, its precoder across N3 FD units (e.g., PMI subbands) is calculated as follows with size N tMatrix W of ×N3 l Given as:

[0090]

[0091] Where, W1, and W f Are as follows:

[0092]

[0093] The precoder matrix (W 2,i ) of layer i (where i = 0, 1) can use the FD compression Matrix to compress the precoding matrix into a matrix with dimensions of 2L X M (where M is network-configured and transmitted via RRC or DCI in the CSI configuration, and M < N3), given as follows: Matrix, given as follows:

[0094]

[0095] Where, the precoding matrix W i (not shown) has P = 2N1N2 rows (spatial domain, number of ports) and N3 columns (frequency domain compression units including RBs or reporting subbands), and where M bases are independently selected for each of layer 0 and layer 1. The matrix consists of linear combination coefficients (amplitude and co-phase), where each element represents the coefficient for a tap of the beam. The matrix can be defined by dimensions 2L X M, where one row corresponds to one spatial beam in W1 (not shown) with dimensions P X 2L (where L is network-configured via RRC), and one entry therein represents the coefficient for a tap of that spatial beam.

[0096] The UE can be configured to report (e.g., CSI report) A subset K0 < 2LM of the linear combination coefficients of the matrix. For example, the UE can report K NZ,i < K0 coefficients shown as shaded squares (unreported coefficients are set to zero) (where K NZ,i corresponds to the maximum number of non-zero coefficients of layer i (where i = 0 or 1), and K0 is network-configured via RRC). In some configurations, The entries in the matrix correspond to The rows in the matrix. In the example shown in the figure, the matrix at layer 0 and the matrix at layer 1 are both 2L X M.

[0097] The matrix consists of basis vectors (each row is a basis vector) used to perform compression in the frequency domain. In the example shown in the figure, the Matrix and layer 1 The matrix includes M=4 FD bases from N3 candidate DFT bases. In some configurations, the UE may report via CSI reporting A subset of the selected basis of the matrix. The M basis is explicitly selected at level 0 and level 1. That is, the M basis selected at level 0 can be the same as / partially overlap with / non-overlap with the M basis selected at level 1.

[0098] The precoder can be written as:

[0099]

[0100] As discussed above, Type II CSI with FD compression can compress N3 subbands via M FD bases. The FD bases are selected / reported as layer-specific. For each layer, the UE reports a subset of 2LM coefficients in total, where the coefficient selection can be layer-specific and the UE can use a bitmap of size 2LM to indicate the selected non-zero coefficients (NZC) and report each NZC after quantization. In some examples, the UE can report up to K0 coefficients per layer, where K NZ,l ≤K0. In some examples, the UE may report up to 2K0 coefficients across all layers, where Those not reported were set to zero.

[0101] The UE may report the CSI in uplink control information (UCI). In some examples, the CSI may be reported in two-part UCI. In some examples, in the first part of the UCI, the UE may send RI, CQI, number of non-zero coefficients (NNZC). In some examples, in the second part of the UCI, the UE may send SD beam selection, FD basis selection, coefficient selection, strongest coefficient indication (SCI), and / or coefficient quantization for supported layers (e.g., layer 0 to RI-1). The SD beam selection may indicate the selected beam (e.g., a subset of 2L beams).

[0102] Example port selection for channel state feedback with analog feedforward

[0103] In some systems (e.g., NR Release 16 and later systems), channel state information (CSI) can be compressed in the spatial domain (SD) and frequency domain (FD). A base station (BS), which may be a next-generation NodeB (gNB), can precode the CSI reference signal (RS) ports and emulate the precoder (e.g., instead of configuring the SD and FD basis for the UE). This is referred to as emulated feedforward.

[0104] Simulating a feed-forward CSI framework:

[0105] According to certain aspects, CSI may be compressed as shown in the following expression:

[0106]

[0107] L is the number of SD bases, M is the number of FD bases, b is the SD basis vector, f is the FD basis vector, and c is the linear combination coefficient used to combine the SD basis and the FD basis.

[0108] As shown in the above formula, in the case of two polarizations, the specific SD basis and the specific FD basis form a matrix G with size P×N3 across N3 subbands k Since there are L SD bases and M FD bases, the final precoder is actually 2LM matrices (i.e., G0,…,G k ) is a linear combination of .

[0109] In some systems (e.g., Rel-16NR or later versions), in the port selection codebook, virtual ports (e.g., specific SD basis and specific FD basis) are used to precode CSI-RS ports on N3 FD units (e.g., FD units can be resource blocks (RBs) or subbands). Figure 4 As shown in FIG, each CSI-RS port (Port 0, Port 1, Port 2, Port 3) is associated with the same SD basis and FD basis across all subbands (e.g., Port 0 is associated with the same SD basis b0 and FD basis b1 across all FD units 0...N3). associated), but rotate on each FD unit or subband (for example, for Port 0, make the FD basis Rotate [0...N3-1]). Figure 4As shown in , each CSI-RS port uses an SD basis and / or FD basis that is different from other CSI-RS ports. In some examples, the BS can obtain spatial reciprocity and delay reciprocity via a sounding reference signal sent from the UE, and then perform precoding using an SD and / or FD basis derived based on the obtained spatial / delay reciprocity.

[0110] The SD basis and FD basis can be simulated by the BS (e.g., gNB) and thus can be transparent to the UE. In this case, the UE may not be aware of the SD basis and FD basis, or may not be configured with the SD basis and FD basis. Instead, the UE may perform CSI-RS port selection, form a precoding matrix indicator (PMI), and calculate linear combination coefficients for the selected CSI-RS. For example, the UE selects K0 CSI-RS ports from a set of P CSI-RS ports. K0 may be configured by the BS. The BS simulates the P CSI-RS ports from N1N2N3 candidate bases.

[0111] The UE may perform a covariance wideband calculation to derive coefficients for the selected CSI-RS ports. The UE may then report K0 wideband coefficients associated with the K0 selected CSI-RS ports.

[0112] Therefore, compared with digital feed-forward CSI feedback, CSI reporting overhead and complexity can be reduced. In addition, there can be increased flexibility with CSI-RS emulation. In addition, the FD unit granularity can be finer (e.g., RB level).

[0113] Example polarization-common and polarization-specific precoding:

[0114] According to certain aspects, CSI-RS port precoding and selection may be polarization-common or polarization-specific.

[0115] For polarization-common port selection, the same port can be used for both polarizations. In some examples, the BS uses the same precoder on corresponding ports in different polarizations. In some examples, the UE assumes an organization of CSI-RS ports. This organization can be configured by the BS or specified in the wireless standard.

[0116] For polarization-common port selection, the first half of the CSI-RS ports can be on polarization 1, and the other half can be on polarization 2; however, other uneven partitioning of ports by polarization is possible. Similar precoding (port-by-port) is performed for the second half of the CSI-RS ports.

[0117] In the case of polarization-common port selection, the PMI for a layer on any FD unit among the N3 FD units can be given by:

[0118]

[0119] in, With size When in line k When there is only one "1" in , and P is the total number of CSI-RS ports, it means that the i-th FD unit is selected on all N3 FD units. k port.c k It can be the same as port i which is on polarization 1. k The associated linear combination coefficients, and It can be the same as port i on polarization 2. k The UE can use a number of CSI-RS port combinations K0 (or K0 / 2). Then, the UE reports as well as or Ports not reported are set to 0.

[0120] In the matrix representation for polarization-common port selection, the PMI for a layer on any of the N3 FD units is:

[0121] W1×W2,

[0122] in,

[0123]

[0124] For size

[0125] And among them

[0126]

[0127] contains the coefficients, and K0 (or K0 / 2) is the number of ports used for combining.

[0128] UE Report as well as or The unreported CSI-RS ports are set to 0.

[0129] For polarization-specific port selection, the BS can use different precoders on CSI-RS ports in different polarizations. For example, the first part of the CSI-RS ports (e.g., 20 CSI-RS ports) can be used for polarization 1, and the second part of the CSI-RS ports (e.g., 12 CSI-RS ports) can be used for polarization 2. In some examples, the UE can select any of the CSI-RS ports for combination.

[0130] With polarization-specific port selection, the PMI for a layer on any of the N3 FD units can be given by:

[0131]

[0132] in, has size P×1, where row i k There is only one "1" in it, P is the total number of CSI-RS ports, which means that the i-th k port.

[0133] UE Report as well as or The unreported CSI-RS ports are set to 0.

[0134] In the matrix representation for polarization-common port selection, the layer-specific PMI on any FD unit among the N3 FD units is:

[0135] W1×W2,

[0136] in, The size is P×K0.

[0137] UE Report as well as or The unreported CSI-RS ports are set to 0.

[0138] Example organization of CSI-RS ports:

[0139] According to certain aspects, the precoding and port organization is transparent to the UE. For example, the BS can emulate the precoder for each port, and the UE can freely select the CSI-RS for combining. In this example, there may not be any configured, defined, or specified organization of the CSI-RS ports. In some examples, this can be used when the port selection is polarization-specific.

[0140] According to certain aspects, precoding and port selection can be non-transparent to the UE. For example, the CSI-RS ports can be organized. This organization can be configured by the base station and / or specified in the wireless standard. In some examples, this can be used when the port selection is polarization-common.

[0141] In some examples, the CSI-RS ports can be organized into a single resource. For example, a portion (e.g., half) of the CSI-RS ports can be applied on polarization 1, and another portion (e.g., the other half) of the CSI-RS ports can be applied on polarization 1. For each portion (e.g., each half), the CSI-RS ports can be divided into groups (e.g., M groups), such as Figure 5 As shown in . Each group of CSI-RS ports can correspond to a specific SD basis or a specific FD basis. In other words, each CSI-RS port within a given group is associated with the same FD basis or SD basis. Within a CSI-RS group, each different CSI-RS port is associated with a different SD basis (when the group is associated with the same FD basis) or with a different FD basis (when the group is associated with the same SD basis), as shown in Figure 5 As shown in .

[0142] In this case, when selecting and reporting the selected CSI-RS, the UE may determine / report the group index (or multiple indices) of the selected CSI-RS port, and may further determine / report the port index of the selected CSI-RS port within the group. The group index and / or CSI-RS port index may be determined / reported as layer-specific or layer-common and rank-specific or rank-common. The port selection within each group may be the same or different. Figure 5 An example of selecting the second and third CSI-RS ports from groups 0, 1, and 3 across both polarizations to calculate the PMI to be reported with the CSI is shown.

[0143] In some examples, CSI-RS ports may be organized across resources, such as Figure 6A and Figure 6BAs shown in . For example, a portion of the CSI-RS ports (e.g., half) can be applied on polarization 1, and another portion of the CSI-RS ports (e.g., the other half). Each resource can be associated with all CSI-RS (i.e., two portions), and each resource can correspond to a specific FD basis or a specific SD basis. In other words, in a resource, all CSI-RS are associated with the same FD (or SD) basis, and then in other resources, all CSI-RS ports are associated with different FD (or SD) bases. Therefore, within each resource, at least for polarization, each CSI-RS port is associated with a different SD basis (when the resource is associated with the same FD basis) or with a different FD basis (when the resource is associated with the same SD basis), as shown in . Figure 6A and Figure 6B As shown in .

[0144] In this case, when selecting and reporting the selected CSI-RS, the UE may determine / report the resource index (indices) of the selected CSI-RS port, and may further determine / report the port index of the selected CSI-RS port within the resource. The resource index and / or CSI-RS port index may be determined / reported as layer-specific or layer-common and rank-specific or rank-common. The CSI-RS port index may be the same or different across different resources.

[0145] Example port selection:

[0146] As mentioned above, the BS can configure the number of CSI-RS ports (e.g., K0) for the UE to use for linear combination. K0 can be configured as rank-common or rank-specific (e.g., different number of ports for different ranks). In some examples, the number of CSI-RS ports for higher ranks can be derived from the number of CSI-RS ports for lower ranks. In some examples, the UE can (freely) select any CSI-RS port from the total P CSI-RS ports, up to the configured number K0 CSI-RS ports per layer, and up to a total of 2K0 CSI-RS ports across all layers.

[0147] According to certain aspects, the BS may further configure the number of CSI-RS port groups or the number of CSI-RS resources for which the user may select CSI-RS ports when configuring the groups or resources as described above. The number of CSI-RS port groups / resources may be equal to the number of FD basis (M) or SD basis (L), depending on whether FD or SD is associated with the group / resource. The BS may further configure the number of CSI-RS ports that the UE may select within the CSI-RS port group / resource. The number of CSI-RS ports within a group / resource may be equal to the number of FD basis (M) or SD basis (L), depending on whether FD or SD is associated with the CSI-RS ports within the group / resource.

[0148] In some examples, with CSI-RS port grouping organization, the group selection may be common for the groups in both parts of the CSI-RS ports (e.g., for the groups in both polarizations), and further, the port selection in the group may also be common in both parts (e.g., as Figure 5). For example, the SD selection and FD selection may be polarization common. In some examples, the group selection may be common for the groups in both parts, but the port selection within the group may be group specific or group pair specific. For example, the UE may select and report group 1 and group 3 for a first plurality of ports, and this also indicates that group 1 and group 3 are selected for a second plurality of ports. However, the port selection / reporting within each group may be different across different groups, e.g., ports 1 and 2 in group 1 are selected for the first plurality of ports, while ports 1 and 3 in group 3 are selected for the first plurality of ports, ports 2 and 4 in group 1 are selected for the second plurality of ports, while ports 2 and 3 in group 3 are selected for the second plurality of ports. Considering that the group index corresponds to the SD basis, and the port index in each group corresponds to the FD basis, this can correspond to selecting the first and third SD basis for both the first and second polarizations, while selecting the first and second FD basis for the first SD basis on the first polarization, the first and third FD basis for the third SD basis on the first polarization, the second and fourth FD basis for the first SD basis on the second polarization, and the second and third FD basis for the third SD basis on the second polarization. In some examples, the group selection can be specific to the groups in the two parts, but the port selection within the group can be group-wide. For example, the UE can select and report groups 1 and 3 for the first plurality of ports, and groups 1 and 4 for the second plurality of ports. However, the port selection / reporting within each group is the same within each group, for example, ports 1 and 2 are selected and reported for all groups. Considering that the group index corresponds to the FD basis and the port index within each group corresponds to the SD basis, this can correspond to selecting the first and second SD basis for both the first polarization and the second polarization, while selecting the 1st and 3rd FD basis for the first and second SD basis on the first polarization, and selecting the 1st and 4th FD basis for the first and second SD basis on the second polarization. In some examples, the group selection can be specific, and the port selection within the group can be group-specific or group-pair-specific.

[0149] In some examples, in the case of CSI-RS resource organization, for CSI-RS resources (e.g., Figure 6A and Figure 6BFor the example resources shown in , the port selection can be common for the CSI-RS ports in the two parts. For example, the same SD and FD are common in the CSI-RS ports associated with the CSI-RS resources in both polarizations. In some examples, the UE can select one or more resources and report via CRI. In addition, the UE can select ports within each resource, and the port selection can be resource common and also common for the two parts (e.g., polarizations). For example, the UE can select and report the 1st and 3rd resources. The UE can then select and report the 1st and 2nd ports for the first plurality of ports, and this also indicates that the 1st and 2nd ports are selected for the first CSI-RS resource for the second plurality of ports, and this also indicates that the 1st and 2nd ports are selected for the first CSI-RS resource for the first plurality and the second plurality of ports. Considering that each resource is associated with a specific SD basis, and each port is associated with a specific FD basis, this implies selecting the 1st and 3rd SD basis and the 1st and 2nd FD basis. In some examples, the UE may select ports within each resource, and the port selection may be resource-common but specific for two parts (e.g., polarizations). For example, the UE may select and report the 1st and 3rd resources. The UE may then select and report the 1st and 2nd ports for the first plurality of ports in the first resource, and may select and report the 1st and 4th ports for the second plurality of ports in the first resource. This also indicates that the 1st and 2nd ports are selected for the first plurality of ports in the third resource, and the 1st and 4th ports are selected for the second plurality of ports in the third resource. Considering that each resource is associated with a specific SD basis and each port is associated with a specific FD basis, this implies selecting the 1st and 3rd SD basis, while for the 1st SD basis, the 1st and 2nd FD basis are selected for the first polarization, and the 1st and 4th FD basis are selected for the second polarization; for the 3rd SD basis, the 1st and 2nd FD basis are selected for the first polarization, and the 1st and 4th FD basis are selected for the second polarization. In some examples, the UE may select ports within each resource, and the port selection may be resource-specific but may be common to both parts (e.g., polarization). For example, the UE may select and report the first and third resources. The UE may then select and report the first and second ports for the first plurality of ports in the first resource, and may select and report the second and third ports for the first plurality of ports in the third resource. This also indicates that the first and second ports are selected for the second plurality of ports in the first resource, and the second and third ports are selected for the second plurality of ports in the third resource.Considering that each resource is associated with a specific SD basis and each port is associated with a specific FD basis, this implies selecting the 1st and 3rd SD basis, while for the 1st SD basis, the 1st and 2nd FD basis are selected for both polarizations; for the 3rd SD basis, the 2nd and 3rd FD basis are selected for both polarizations. In some examples, the UE can select ports within each resource, and the port selection can be resource-specific and specific for both parts (e.g., polarization). For example, the UE can select and report the 1st and 3rd resources. The UE can then select and report the 1st and 2nd ports for the first plurality of ports in the first resource, and the 1st and 3rd ports for the second plurality of ports in the first resource. Additionally, the UE can select and report the 1st and 4th ports for the first plurality of ports in the second resource, and the 2nd and 4th ports for the second plurality of ports in the third resource. Considering that each resource is associated with a specific SD basis and each port is associated with a specific FD basis, this implies selecting the 1st and 3rd SD basis. Then, for the 1st SD basis, the 1st and 2nd FD bases are selected for the first polarization, and the 1st and 3rd FD bases are selected for the second polarization; for the 3rd SD basis, the 1st and 4th FD bases are selected for the first polarization, while the 2nd and 4th FD bases are selected for the second polarization.

[0150] After the group-based selection, the BS may further configure the number of CSI-RS ports for the UE to use for linear combination, e.g., K0 ≤ 2LM, where L (or M) may correspond to the number of groups / resources to be selected, and M (or L) corresponds to the number of ports to be selected in each resource / group. K0 may be configured as rank-common or rank-specific (e.g., different numbers of ports for different ranks). In some examples, the number of CSI-RS ports for higher ranks may be derived from the number of CSI-RS ports for lower ranks. In some cases, when rank-specific, M or L may be configured as the number for ranks 1 and 2, while a smaller M or L may be configured for higher ranks, thereby having comparable overhead for different ranks.

[0151] The UE may report the actual number K of non-zero CSI-RS ports selected for combining NZ ≤K0. The UE is free to report (actually non-zero) port selection from a total of P ports The selection can be polarization-common or polarization-specific.The selection can be layer-common or layer-specific.

[0152] According to certain aspects, the BS may configure a subset of ports from the total number of ports. In this case, the port selection for each layer of each rank should be selected from the configured subset. This configuration may be rank-specific.

[0153] Figure 7 7 is a flow diagram illustrating example operations 700 for wireless communication in accordance with certain aspects of the present disclosure. Operations 700 may be performed by, for example, a UE (e.g., UE 120a in wireless communication network 100). Operations 700 may be implemented on one or more processors (e.g., Figure 2 In addition, for example, the communication may be performed via one or more antennas (e.g., Figure 2 The transmission and reception of signals by the UE in operation 700 may be implemented by antenna 252 of the UE. In certain aspects, the transmission and / or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller / processor 280) that obtains and / or outputs signals.

[0154] Operation 700 may begin at 705 by selecting one or more CSI-RS ports from a plurality of CSI-RS ports for the UE to report CSI. The port selection may include selecting any CSI-RS port from the plurality of CSI-RS ports or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. In some examples, the port selection is polarization-specific or polarization-common. In some examples, the number of CSI-RS ports may be greater than 32. In some examples, the UE receives a configuration of a subset of the plurality of CSI-RS ports from a BS, and selects the one or more CSI-RS ports from the subset of the configured CSI-RS ports. The subset may be configured as rank-specific.

[0155] According to certain aspects, the UE selects any CSI-RS port among the plurality of CSI-RS ports (eg, for polarization-specific port selection).

[0156] According to certain aspects, the UE determines a grouping of the plurality of CSI-RS ports and selects the one or more CSI-RS ports based at least in part on the grouping (e.g., for polarization-common port selection). In some examples, the grouping is configured at the UE by a base station or based on a wireless standard. In some examples, the UE determines the grouping includes determining that a first portion (e.g., half) of the plurality of CSI-RS ports are associated with a first polarization and a second portion (e.g., the other half) of the plurality of CSI-RS ports are associated with a second polarization.

[0157] In some examples, the UE determines a first plurality of groups of CSI-RS ports in a first portion and a second plurality of groups of CSI-RS ports in a second portion. In some examples, within each of the first and second pluralities of groups, each group is associated with a specific SD basis or FD basis (which may be transparent to the UE). In some examples, within each of the groups, each CSI-RS port is associated with a specific one of the other of the SD or FD basis.

[0158] In some examples, the UE receives a configuration from the BS for the number of CSI-RS port groups for the UE to report linear combination coefficients. In this case, the UE can select the one or more CSI-RS ports from up to the configured number of CSI-RS port groups. In some examples, the UE receives a configuration for the number of CSI-RS ports within each CSI-RS port group for the UE to report linear combination coefficients. In this case, the UE can select up to the configured number of CSI-RS ports from each of the selected CSI-RS port groups.

[0159] In some examples, the UE determines a plurality of CSI-RS resources. Each CSI-RS resource includes a first portion and a second portion of the CSI-RS port. The UE may receive a configuration of the number of CSI-RS resources for the UE to report linear combination coefficients from the BS, and select the one or more CSI-RS ports from up to the configured number of CSI-RS resources. Each CSI-RS resource may correspond to a specific SD basis or FD basis. Within each CSI-RS resource: each CSI-RS port in the first portion of CSI-RS ports is associated with a specific one of the other of the SD basis or the FD basis; and each CSI-RS port in the second portion of CSI-RS ports is associated with a different one of the other of the SD basis or the FD basis.

[0160] In some examples, the UE receives from the BS a configuration of the number of CSI-RS ports within each CSI-RS resource for the UE to report linear combination coefficients. In this case, the UE selects the configured number of CSI-RS ports from each of the selected CSI-RS resources. The UE may provide the selected CSI-RS ports by indicating one or more CSI-RS resource indices, one or more CSI-RS port indices, or both, for indicating the selected CSI-RS ports associated with the CSI report.

[0161] In 710, the UE determines a PMI formed by a linear combination of one or more selected CSI-RS ports.

[0162] The UE calculates at least wideband linear combination coefficients for the selected CSI-RS ports at 715. In some examples, the UE calculates wideband linear combination coefficients across all FD units for each selected CSI-RS port.

[0163] In 720, the UE provides the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to the BS in a CSI report. In some examples, the UE provides the selected one or more CSI-RS ports by indicating one or more CSI-RS port group indices, one or more CSI-RS port indices, or both. In some examples, the UE receives from the BS a configuration of a maximum number of CSI-RS ports per layer or per rank for which the UE reports the linear combination coefficients. In some examples, the UE reports to the BS an indication of the number of non-zero CSI-RS ports associated with the CSI report that is equal to or less than the configured maximum number of CSI-RS ports. In some examples, the UE reports to the BS an indication of the selected non-zero CSI-RS ports associated with the CSI report that is equal to or less than the configured maximum number of CSI-RS ports.

[0164] In some examples, the FD unit size is smaller than the subband.

[0165] Figure 8 800 is a flow diagram illustrating example operations 800 for wireless communication in accordance with certain aspects of the present disclosure. Operations 800 may be performed by, for example, a BS (e.g., BS 110a in wireless communication network 100). Operations 800 may be complementary operations performed by the BS to operations 700 performed by the UE. Operations 800 may be implemented on one or more processors (e.g., Figure 2 In addition, for example, the communication may be performed via one or more antennas (e.g., Figure 2 The transmission and reception of signals by the BS in operation 800 may be accomplished by antenna 234 of the BS. In certain aspects, the transmission and / or reception of signals by the BS may be accomplished via a bus interface of one or more processors (e.g., controller / processor 240) that obtains and / or outputs signals.

[0166] Operation 800 may begin at 805 by sending a CSI request to a UE for a PMI formed by a linear combination of a plurality of CSI-RS ports selected by the UE. The port selection may include selecting any CSI-RS port from the plurality of CSI-RS ports or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports. In some examples, the port selection is based on whether the grouping of the plurality of CSI-RS ports is polarization-specific or polarization-common. A precoder for the CSI-RS port may include a specific SD basis and an FD basis to emulate the CSI-RS. Different precoders may be associated with different SD bases, different FD bases, or both.

[0167] In 810, the BS receives a CSI report including at least port selection and wideband linear combination coefficients from the UE.

[0168] A first portion of the plurality of CSI-RS ports may be associated with a first polarization, and a second portion of the plurality of CSI-RS ports may be associated with a second polarization. In some examples, corresponding CSI-RS ports in the first and second portions have the same precoder. In some examples, corresponding CSI-RS ports in the first and second portions have different precoders.

[0169] According to a certain aspect, the BS determines the grouping of CSI-RS ports by grouping the CSI-RS ports in the first part into a first plurality of groups and grouping the CSI-RS ports in the second part into a second plurality of groups. Each group within each of the first and second plurality of groups can be associated with a common specific SD basis or FD basis, and within each of the groups, all CSI-RS ports are associated with a specific one of the other of the SD basis or FD basis. The BS can configure the number of CSI-RS port groups for the UE to report linear combination coefficients. The BS can configure the number of CSI-RS ports for the UE to report linear combination coefficients within each CSI-RS port group to the UE. The CSI report may include one or more CSI-RS port group indexes, one or more CSI-RS port indexes, or both for indicating the CSI-RS ports associated with the CSI report.

[0170] According to certain aspects, the BS determines the grouping of CSI-RS ports by determining multiple CSI-RS resources. Each CSI-RS resource may include the first and second parts of the CSI-RS ports and a specific SD basis or FD basis. Within each resource, each CSI-RS port in the first part of the CSI-RS ports may be associated with a specific one of the other of the SD basis or the FD basis; and each CSI-RS port in the second part of the CSI-RS ports is associated with the specific one of the other of the SD basis or the FD basis. In some examples, the BS configures the UE with the number of CSI-RS resources for the UE to report linear combination coefficients. In some examples, the BS configures the UE with the number of CSI-RS ports within each CSI-RS resource for the UE to report linear combination coefficients. The CSI report may include one or more resource indexes, one or more CSI-RS port indexes, or both for indicating the CSI-RS ports associated with the CSI report.

[0171] According to certain aspects, a BS may configure, to a UE, a maximum number of CSI-RS ports per layer or per rank for which the UE reports linear combination coefficients. The CSI report may include an indication of a number of non-zero CSI-RS ports associated with the CSI report that is equal to or less than the configured maximum number of CSI-RS ports. The CSI report may include an indication of selected non-zero CSI-RS ports associated with the CSI report that is equal to or less than the configured maximum number of CSI-RS ports.

[0172] According to certain aspects, the BS may configure a subset of the plurality of CSI-RS ports to the UE, from which the UE may select up to the maximum number of CSI-RS ports per layer. The subset may be configured as rank-specific.

[0173] According to certain aspects, the plurality of CSI-RS ports may include more than 32 CSI-RS ports.

[0174] According to certain aspects, the FD unit size can be smaller than the sub-band.

[0175] Figure 9 The diagrams may include a method configured to perform operations for the techniques disclosed herein (e.g., Figure 7900 includes various components (e.g., corresponding to functional module components) of the communication device 900. The communication device 900 includes a processing system 902 coupled to a transceiver 908 (e.g., a transmitter and / or a receiver). The transceiver 908 is configured to transmit and receive signals for the communication device 908, such as the various signals described herein, via an antenna 910. The processing system 902 can be configured to perform processing functions for the communication device 900, including processing signals received and / or to be transmitted by the communication device 900.

[0176] The processing system 902 includes a processor 904 coupled to a computer-readable medium / memory 912 via a bus 906. In certain aspects, the computer-readable medium / memory 912 is configured to store instructions (e.g., computer-readable code) that, when executed by the processor 904, cause the processor 904 to perform Figure 7 The operations shown or other operations for performing the various techniques discussed herein for port selection for channel state feedback with analog feedforward. In certain aspects, the computer-readable medium / memory 912 stores, in accordance with aspects of the present disclosure: code 914 for selecting a CSI-RS port; code 916 for determining a PMI formed by the selected CSI-RS port; code 918 for calculating wideband linear combination coefficients for the selected CSI-RS port; and code 920 for providing the selected CSI-RS port and the calculated wideband coefficients to the BS. In certain aspects, the processor 904 has circuitry configured to implement the code stored in the computer-readable medium / memory 912. In accordance with aspects of the present disclosure, the processor 904 includes circuitry 922 for selecting a CSI-RS port; circuitry 924 for determining a PMI formed by the selected CSI-RS port; circuitry 926 for calculating wideband linear combination coefficients for the selected CSI-RS port; and circuitry 928 for providing the selected CSI-RS port and the calculated wideband coefficients to the BS.

[0177] Figure 10 The diagrams may include a method configured to perform operations for the techniques disclosed herein (e.g., Figure 8 1000 includes various components (e.g., corresponding to functional module components) of the communication device 1000. The communication device 1000 includes a processing system 1002 coupled to a transceiver 1008 (e.g., a transmitter and / or a receiver). The transceiver 1008 is configured to transmit and receive signals for the communication device 1000, such as the various signals described herein, via an antenna 1010. The processing system 1002 can be configured to perform processing functions for the communication device 1000, including processing signals received and / or to be transmitted by the communication device 1000.

[0178] The processing system 1002 includes a processor 1004 coupled to a computer-readable medium / memory 1012 via a bus 1006. In some aspects, the computer-readable medium / memory 1012 is configured to store instructions (e.g., computer-readable code) that, when executed by the processor 1004, cause the processor 1004 to perform Figure 8 The operations shown or other operations for performing the various techniques discussed herein for port selection for channel state feedback with analog feedforward. In certain aspects, the computer-readable medium / memory 1012 stores, in accordance with aspects of the present disclosure: code 1014 for sending a CSI request for a PMI to a UE; and code 1016 for receiving a CSI report from the UE. In certain aspects, the processor 1004 has circuitry configured to implement the code stored in the computer-readable medium / memory 1012. In accordance with aspects of the present disclosure, the processor 1004 includes circuitry 1018 for sending a CSI request for a PMI to a UE; and circuitry 1020 for receiving a CSI report from the UE.

[0179] Example mapping of virtual ports to CSI-RS ports

[0180] As noted above, a BS (e.g., BS 110a in wireless communication network 100) can configure the number of CSI-RS port groups or CSI-RS resources from which a UE (e.g., UE 120a in wireless communication network 100) can select CSI-RS ports. In some cases, to achieve good performance, Rel-17 FDD-based CSI reciprocity can use a larger number of SD-FD base pairs (e.g., 32 or 64) to perform CSI-RS precoding. SD-FD base pairs can correspond to virtual ports.

[0181] The UE may select a CSI-RS port to report CSI. In some aspects, the UE may perform a one-to-one mapping between virtual ports and CSI-RS ports to perform port-selective CSI measurement and reporting. In some aspects, the UE may perform a many-to-one mapping between virtual ports and CSI-RS ports to perform port-selective CSI measurement and reporting.

[0182] One-to-one mapping:

[0183] According to certain aspects, the UE may perform a one-to-one mapping technique in which each CSI-RS port is precoded (or beamformed) via a specific virtual port. In the one-to-one mapping technique, the UE may select a CSI-RS port for which CSI is to be reported across multiple CSI-RS resources. This may enable selection of more than 32 ports (e.g., 64 virtual ports or SD-FD basis pairs) since current technical specifications may only support 32 ports per CSI-RS resource. For example, the UE may freely select a CSI-RS port from any CSI-RS resource in the CSI-RS resource and from multiple CSI-RS resources in the CSI-RS resource. In one non-limiting example, each CSI-RS resource in the multiple CSI-RS resources may include multiple CSI-RS ports. In another non-limiting example, each CSI-RS resource in the multiple CSI-RS resources may be mapped to a virtual port (e.g., a pair of SD basis and FD basis). In another non-limiting example, each CSI-RS resource in the multiple CSI-RS resources may be divided into at least two parts. In another non-limiting example, to save CSI-RS overhead, each CSI-RS resource in the plurality of CSI-RS resources may be associated with a density less than 1. The density may be 0.5 or 0.25, which may mean that a CSI-RS port is transmitted every two RBs or every four RBs.

[0184] In some examples, the UE may span K s CSI-RS resources select CSI-RS ports. Each CSI-RS resource can include P CSI-RS ports. Then, the UE can s *P CSI-RS In some examples, P in each CSI-RS resource is selected (freely) from X ports. CSI-RS The ports can be divided into two parts. The first part includes the ports transmitting according to the first polarization, and the second part includes the ports transmitting according to the second polarization. The UE can then receive the K s *P CSI-RS / 2 ports (freely) select X ports and also select the same port positions in the second part. s and P CSI-RS The value of can vary. In one non-limiting example, K s It can be 2 and P CSI-RS It can be 32. In another non-limiting example, K s Can be 64, and P CSI-RS It can be 1. In another non-limiting example, K sCan be 4, and P CSI -RS can be 8.

[0185] In some examples, the UE may further determine the span K s In some examples, the UE may determine that N resources are grouped, thereby obtaining K s / N groups. In some examples, the UE may determine the two resources as resource pairs, and the number of pairs is equal to K s / 2. In some examples, the UE may receive a configuration indicating valid groups or pairs from all possible groups or pairs. In some examples, the configuration may be via Bitmap or via The number of bit combinations indicates the total In some examples, this configuration can be done via bitmap or The number of bit combinations indicates the total S pairs out of the pairs are valid. In some examples, the UE can determine that every two resources are a pair based on the order of the resources. In some examples, the UE can determine that every N resources are grouped based on the order of the resources. For example, in the trigger state configuration, the CSI report can be associated with an NZP CSI-RS resource set including resources ID0, ID1, ID2 and ID3. The UE can determine that CSI-RS resources ID0 and ID1 are a pair and CSI-RS resources ID2 and ID3 are a pair. In some cases, the UE may further report an indication indicating a preferred (one or more) CSI-RS resource group or pair. The indicator may be provided via a multi-CSI-RS resource indicator indicating a resource group or resource pair rather than a single resource. The bit width of the indicator may depend on the number of possible groups or possible pairs. The reported PMI including port selection and linear combination coefficients is associated with the resources and ports in the resource group or pair. In some cases, port selection across multiple resources and resource grouping / pairing is only applicable when the total number of ports in each group is greater than 32 (e.g., the total number of ports in each group / pair is 48 and 64, obtained by 24+24 or 32+32, respectively).

[0186] In some examples, the density value associated with each CSI-RS resource may be 0.5. For example, the CSI-RS in each CSI-RS resource may be transmitted only on even resource blocks (RBs) or only on odd RBs. In some examples, the density value for each CSI-RS resource may be less than 0.5. For example, if the density is equal to 0.25, the CSI-RS in each CSI-RS resource may be transmitted only on RB-comb 1 (RB0, RB4, RB8, etc.), or only on RB-comb 2 (RB1, RB5, RB9, etc.), or only on RB-comb 3 (RB2, RB6, RB10, etc.), or only on RB-comb 4 (RB3, RB7, RB11, etc.). When the density value for each CSI-RS resource may be less than 0.5, port selection may only apply to the Rel-17 enhanced port selection codebook.

[0187] In some examples, the CSI-RS ports in the plurality of CSI-RS resources may be reindexed. The reindexing of these CSI-RS ports may be based on the resource index. For example, to calculate the CQI, the pth CSI-RS port in the mth CSI-RS resource may be reindexed to 3000+m*P CSI-RS +p. In some examples, a virtual physical downlink shared channel (PDSCH) can be used to calculate the CQI. The virtual PDSCH can be generated as:

[0188]

[0189] W may include a PMI, which may be mapped to a virtual CSI-RS port or a re-indexed CSI-RS port.

[0190] In certain aspects, a UE may receive a resource mapping configuration that may indicate a combined CSI-RS resource. The combined CSI-RS resource may include one or more component CSI-RS resources. Each component CSI-RS resource may include multiple CSI-RS ports. In some examples, the combined CSI-RS resource may include a number P of CSI-RS ports that may be formed by the one or more component CSI-RS resources. Each of the component CSI-RS resources may include less than P CSI-RS ports (e.g., there may be N CSI-RS ports with P1, P2, ..., P N The number of CSI-RS ports in the combined CSI-RS resource may be determined by Given). In the resource mapping configuration, the UE may receive a number N of resource mapping configurations. Each resource mapping configuration may include information such as the number of CSI-RS ports, code division multiplexing (CDM) type, frequency domain allocation (e.g., RE position of each CDM group, starting RB and / or total bandwidth of CSI-RS), time domain allocation (e.g., first starting symbol and second starting symbol), power control offset, density (e.g., CSI-RS port is transmitted every RB, every two RBs, or every four RBs), etc. The UE may receive the first P1 CSI-RS ports following the first resource mapping configuration, then receive the second P2 CSI-RS ports (after the first P1 port) following the second resource mapping configuration, and then receive the P following the kth resource mapping configuration. k CSI-RS ports (in front of P1+P2+…+P k-1 ports). In the illustrated example, the resource mapping configuration may include 48 CSI-RS port resources configured via two resource mappings, each of which includes 24 CSI-RS port resources with a density of 0.5. The resource mapping may include 64 CSI-RS port resources configured via 2 resource mappings, each of which includes 32 CSI-RS port resources with a density of 0.5. The CSI-RS ports transmitted according to the k-th resource mapping configuration may be indexed as Where s is the CDM sequence index, j is the CDM group index of each k-th resource mapping configuration, L = {1, 2, 4, 8} is the number of CSI-RS ports per CDM group, and P k′ is the number of CSI-RS ports given by the k'th resource mapping configuration. If all resource mapping configurations include the same number of CSI-RS ports P', then the CSI-RS ports sent according to the k'th resource mapping configuration can be indexed as p = 3000 + s + jL + (k-1) × P'.

[0191] Many-to-one mapping:

[0192] The UE may perform a many-to-one mapping technique. In the many-to-one mapping technique, each CSI-RS port is precoded (or beamformed) via multiple virtual ports (e.g., SD-FD basis pairs), and the UE may select a CSI-RS port within one of the multiple CSI-RS resources to report CSI. In one non-limiting example, each of the multiple CSI-RS resources may include multiple CSI-RS ports. In another non-limiting example, each of the multiple CSI-RS resources may be mapped to multiple virtual ports (e.g., multiple pairs of SD basis and FD basis).

[0193] In some examples, the UE may receive a first number of CSI-RS ports within a CSI-RS resource in the plurality of CSI-RS resources. The UE may determine whether the first number of CSI-RS ports is mapped to a second number of virtual CSI-RS ports, and each virtual CSI-RS port is precoded via a pair of SD and FD bases. The second number may be greater than the first number. In some cases, the UE may determine whether each of the first number of CSI-RS ports is mapped to more than one virtual CSI-RS port in the second number of virtual CSI-RS ports (e.g., multiple pairs of SD and FD bases). When each of the first number of CSI-RS ports can be mapped to more than one virtual CSI-RS port in the second number of virtual CSI-RS ports (e.g., multiple pairs of SD-FD bases), the UE may select one or more virtual CSI-RS ports (e.g., SD-FD base pairs) from the second number of virtual CSI-RS ports (i.e., SD-FD base pairs). The UE may select one or more virtual CSI-RS ports by first selecting one or more CSI-RS ports and then selecting virtual CSI-RS ports associated with the selected one or more CSI-RS ports.

[0194] In some examples, the UE may select a CSI-RS port in one of Ks resources (eg, CSI-RS resources). Each resource may include P CSI-RS Ports (eg, CSI-RS ports). CSI-RS Each of the ports can be mapped to multiple virtual CSI-RS ports (e.g., multiple pairs of SD and FD bases). To perform (virtual) port selection in one CSI-RS resource, the UE can perform a many-to-one mapping technique. The UE can then determine P CSI-RS is mapped to P>P CSI-RS virtual ports, and select X virtual ports from the P virtual ports. In some examples, each P CSI-RS The ports can be divided into two parts. The first part includes virtual ports transmitted according to the first polarization, and the second part includes virtual ports transmitted according to the second polarization. Similarly, the virtual ports mapped to the P CSI-RS The first part of the virtual ports in the ports are sent according to the first polarization and mapped to the P CSI-RS The second part of the virtual ports in the ports are sent according to the second polarization. Then, the UE can transmit the virtual ports according to the first polarization. CSI-RS / 2 ports determine P / 2 virtual ports, and select X virtual ports from the P / 2 virtual ports, and also select the same virtual port positions in the second part.

[0195] Pairing group:

[0196] In some aspects, one or more CSI-RS virtual ports in the same group (i.e., SD-FD base pair) can be mapped to the same CSI-RS port. In some aspects, the one or more CSI-RS virtual ports in different groups can be mapped to different CSI-RS ports. In some examples, 64 virtual CSI-RS ports can be divided into 32 groups. There can be two ports in each group, such as virtual CSI-RS port 0 and virtual CSI-RS port 32 in the first group, virtual CSI-RS port 1 and virtual CSI-RS port 33 in the second group, and so on. According to this pairing grouping method, as shown in FIG. Figure 11 As shown in , CSI-RS port 3000 can be associated with virtual CSI-RS ports 0 and 32 (i.e., pairing 0 and 32 of the SD-FD base), and CSI-RS port 3001 can be associated with virtual CSI-RS ports 1 and 33 (i.e., pairing 1 and 33 of the SD-FD base), and so on.

[0197] In some aspects, one or more virtual CSI-RS ports mapped to the same CSI-RS port may be transmitted on different resource blocks. For example, a first CSI-RS port on a first set of resource blocks may correspond to a first virtual CSI-RS port (i.e., may be transmitted via a first pair of SD-FD bases), and a first CSI-RS port on a second set of resource blocks may correspond to a second virtual CSI-RS port (i.e., may be transmitted via a second pair of SD-FD bases). In some examples, there may be 32 ports (P_CSIRS = 32 ports) and 64 virtual CSI-RS ports (i.e., P = 64 pairs of SD-FD bases). According to this pairing grouping method, as Figure 11 As shown in , the CSI-RS ports 3000-3001 located on the even resource blocks can correspond to the virtual CSI-RS ports 0-31 respectively (i.e., can be transmitted via the SD-FD base pairs 0-31), and the CSI-RS ports 3000-3001 on the odd resource blocks can correspond to the virtual CSI-RS ports 32-63 respectively (i.e., can be transmitted via the SD-FD base pairs 32-63).

[0198] In some aspects, one or more pairs of SD-FD bases in the same group transmitted to the same set of resource blocks may be mapped to different CSI-RS ports. In some examples, group 0 (or 1) may be associated with virtual CSI-RS ports 0-31 (i.e., SD-FD base pair 0-31) (or virtual CSI-RS ports 32-63 (i.e., SD-FD base pair 32-63)) that may be transmitted on even (or odd) resource blocks mapped to CSI-RS ports 0-31.

[0199] In some cases, a resource's P CSI-RS CSI-RS ports are mapped to P = N*P CSI-RS virtual ports (i.e., precoded via P SD-FD base pairs). P transmitted on different RB combs CSI-RS CSI-RS ports can be mapped to different virtual CSI-RS ports. In some cases, the P on RB comb 1 (ie, RB0, RBN, RB 2N, etc.) CSI-RS CSI-RS ports are mapped to virtual ports 0-P CSI-RS -1; P on RB comb 2 (i.e., RB1, RBN+1, RB 2N+1, etc.) CSI-RS CSI-RS ports can be mapped to virtual ports P CSI-RS to 2P CSI-RS -1; P on RB comb n (i.e., RBn-1, RBN+n, RB 2N+n, etc.) CSI-RS CSI-RS ports can be mapped to virtual ports (n-1)*P CSI-RS to n*P CSI-RS -1.

[0200] In some aspects, the UE may (freely) select any one or more virtual ports (i.e., SD-FD basis pairs) for CSI measurement and reporting. For this purpose, the UE may determine the CSI-RS port index based on the mapping between the CSI port and the virtual CSI-RS port (i.e., SD-FD basis pair). In some examples, the p-th CSI-RS port transmitted on the m-th resource block set may be re-indexed as the virtual port 3000+m*P+p according to the CSI-RS port index. The UE may use the virtual CSI-RS port index to select the virtual CSI-RS port (e.g., SD-FD basis pair) for which to report CSI. In some examples, a PDSCH may be used for the calculation of the CQI. The virtual PDSCH may be generated as:

[0201]

[0202] W may include a port selection PMI, and the port selection PMI includes a port selection matrix and coefficients for combining the CSI-RS ports.

[0203] In some aspects, when a UE can select a virtual CSI-RS port (e.g., SD-FD pair) on a virtual port group basis, the UE can send multiple signalings. Initially, the UE can send a first signaling that can indicate the selected virtual port group (i.e., SD-FD pair group). Next, the UE can send a second signaling that can indicate one or more selected virtual CSI-RS ports (i.e., SD-FD pairs) from the selected virtual port group (SD-FD pair group). In some aspects, the UE can first indicate the CSI-RS port selection and then indicate the virtual port selection, which indicates the selected virtual CSI-RS port associated with the selected CSI-RS port.

[0204] Ability Indication:

[0205] In some aspects, the UE may send capability signaling to the BS. In one non-limiting example (mode 1), the capability signaling may indicate the UE's ability to determine a one-to-one mapping between a CSI-RS port and a virtual CSI-RS port (i.e., an SD-FD basis pair) and select a CSI-RS port across multiple CSI-RS resources (e.g., using a one-to-one mapping). In another non-limiting example (mode 2), the capability signaling may indicate the UE's ability to determine a many-to-one mapping between a virtual CSI-RS port and a CSI-RS port to select a CSI-RS port from within a single CSI-RS resource (e.g., using a many-to-one mapping). In some cases, the network may configure the corresponding mode based on the UE capability report. In some cases, if the UE indicates support for both modes, the network may selectively configure one of the two modes to the UE.

[0206] Example aspects

[0207] In a first aspect, a method for wireless communication performed by a user equipment (UE) includes: selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the UE to report CSI, wherein the port selection includes selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; calculating at least a wideband linear combination coefficient for the selected CSI-RS port; and providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a base station (BS) in a CSI report.

[0208] In the second aspect, alone or in combination with the first aspect, wideband linear combination coefficients are calculated across all frequency domain (FD) units for each selected CSI-RS port.

[0209] In a third aspect, alone or in combination with one or more of the first and second aspects, the port selection is polarization specific or polarization common.

[0210] In the fourth aspect, alone or in combination with one or more of the first to third aspects, selecting the one or more CSI-RS ports for the UE to report CSI includes: determining a grouping of the multiple CSI-RS ports; and selecting the one or more CSI-RS ports based at least in part on the grouping.

[0211] In the fifth aspect, alone or in combination with one or more of the first to fourth aspects, the UE determines the grouping of the multiple CSI-RS ports by: determining a first part of the multiple CSI-RS ports; and determining a second part of the multiple CSI-RS ports.

[0212] In the sixth aspect, alone or in combination with one or more of the first to fifth aspects, a first portion of the plurality of CSI-RS ports is associated with a first polarization; and a second portion of the plurality of CSI-RS ports is associated with a second polarization.

[0213] In the seventh aspect, alone or in combination with one or more of the first to sixth aspects, the UE determines the grouping of the multiple CSI-RS ports by: determining a first plurality of groups of CSI-RS ports in the first part; and determining a second plurality of groups of CSI-RS ports in the second part.

[0214] In the eighth aspect, alone or in combination with one or more of the first to seventh aspects, all CSI-RS ports within a specific group of the first and second multiple groups are associated with a common specific spatial domain (SD) or frequency domain (FD) basis; and within each of the groups, each specific CSI-RS port is associated with a specific one of the SD basis or the other of the FD basis.

[0215] In the ninth aspect, alone or in combination with one or more of the first to eighth aspects, the UE receives, from the BS, a configuration of the number of CSI-RS port groups for the UE to report linear combination coefficients, wherein the selection includes selecting CSI-RS ports from up to the configured number of CSI-RS port groups.

[0216] In the tenth aspect, alone or in combination with one or more of the first to ninth aspects, the UE receives from the BS a configuration of the number of CSI-RS ports within each CSI-RS port group for the UE to report linear combination coefficients, wherein the selection includes selecting up to the configured number of CSI-RS ports from each of the selected CSI-RS port groups.

[0217] In the eleventh aspect, alone or in combination with one or more of the first to tenth aspects, the UE provides the selected one or more CSI-RS ports by indicating one or more CSI-RS port group indices, one or more CSI-RS port indices, or both.

[0218] In the twelfth aspect, alone or in combination with one or more of the first to eleventh aspects, the UE provides the selected one or more CSI-RS ports by: providing one or more CSI-RS port group indexes for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port group indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port group indexes for the first plurality of CSI-RS ports; and / or providing one or more CSI-RS port indexes for a first CSI-RS port group, wherein the one or more CSI-RS port indexes for the remaining one or more CSI-RS port groups are determined based on the one or more CSI-RS port indexes for the first CSI-RS port group.

[0219] In the thirteenth aspect, alone or in combination with one or more of the first to twelfth aspects, the UE determines the grouping of the multiple CSI-RS ports by: determining multiple CSI-RS resources, each CSI-RS resource including a first part and a second part of the CSI-RS port; and receiving a configuration of the number of CSI-RS resources for the UE to report linear combination coefficients from the BS, and the UE selects CSI-RS ports from up to the configured number of CSI-RS resources.

[0220] In the fourteenth aspect, alone or in combination with one or more of the first to thirteenth aspects, all CSI-RS ports within a specific CSI-RS resource are associated with a specific spatial domain (SD) basis or a frequency domain (FD) basis; and within each CSI-RS resource, each specific CSI-RS port in a first part of the CSI-RS ports is associated with a specific one of the other of the SD basis or the FD basis; and each specific CSI-RS port in a second part of the CSI-RS ports is associated with the specific one of the other of the SD basis or the FD basis.

[0221] In the fifteenth aspect, alone or in combination with one or more of the first to fourteenth aspects, the UE receives from the BS a configuration of the number of CSI-RS ports within each CSI-RS resource for the UE to report linear combination coefficients, wherein the selection includes selecting up to the configured number of CSI-RS ports from each of the selected CSI-RS resources.

[0222] In the sixteenth aspect, alone or in combination with one or more of the first to fifteenth aspects, the UE provides the selected one or more CSI-RS ports by indicating one or more CSI-RS resource indices, one or more CSI-RS port indices, or both, for indicating the selected CSI-RS ports associated with the CSI report.

[0223] In the seventeenth aspect, alone or in combination with one or more of the first to sixteenth aspects, the UE provides the selected one or more CSI-RS ports by: providing one or more CSI-RS resource indices for the first plurality of CSI-RS ports, wherein the one or more CSI-RS resource indices for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS resource indices for the first plurality of CSI-RS ports; providing one or more CSI-RS port indices for a first CSI-RS resource, wherein the one or more CSI-RS port indices for the remaining one or more CSI-RS resources are determined based on the one or more CSI-RS port indices for the first CSI-RS resource; and / or providing one or more CSI-RS port indices for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port indices for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port indices for the first plurality of CSI-RS ports.

[0224] In the eighteenth aspect, alone or in combination with one or more of the first to seventeenth aspects, the UE receives from the BS a configuration of a maximum number of CSI-RS ports per layer or per rank for the UE to report linear combination coefficients.

[0225] In the nineteenth aspect, alone or in combination with one or more of the first to eighteenth aspects, the UE reports to the BS an indication of the number of non-zero CSI-RS ports associated with the CSI report that is equal to or smaller than the maximum number of configured CSI-RS ports.

[0226] In the twentieth aspect, alone or in combination with one or more of the first to nineteenth aspects, the UE reports to the BS an indication of the selected non-zero CSI-RS ports associated with the CSI report that are equal to or smaller than the maximum number of configured CSI-RS ports.

[0227] In aspect 21, alone or in combination with one or more of aspects 1 to 20, the UE receives a configuration of a subset of the multiple CSI-RS ports from the BS, wherein the selecting of one or more CSI-RS ports for the UE to report CSI includes selecting a CSI-RS port from the subset of the configured CSI-RS ports.

[0228] In the twenty-second aspect, alone or in combination with one or more of the first to twenty-first aspects, the subset is configured to be rank-specific.

[0229] In the twenty-third aspect, alone or in combination with one or more of the first to twenty-second aspects, the plurality of CSI-RS ports includes more than 32 CSI-RS ports.

[0230] In the twenty-fourth aspect, alone or in combination with one or more of the first to twenty-first aspects, the frequency domain (FD) unit size is smaller than the sub-band.

[0231] In the twenty-fifth aspect, alone or in combination with the first aspect, selecting any of the CSI-RS ports for the UE to report CSI includes: selecting any of the CSI-RS ports across multiple CSI-RS resources, wherein each CSI-RS resource includes multiple CSI-RS ports.

[0232] In the twenty-sixth aspect, alone or in combination with the twenty-fifth aspect, the UE determines a resource grouping or a resource pairing based on the multiple CSI-RS resources, wherein the selection of the CSI-RS port is performed across resources within the same resource grouping or the same resource pairing.

[0233] In the twenty-seventh aspect, alone or in combination with one or more of the twenty-fifth and twenty-sixth aspects, the UE determines resource grouping or resource pairing based on a configuration received from the BS, based on an order of CSI-RS resources, or a combination thereof.

[0234] In aspect 28, alone or in combination with one or more of aspects 25 to 27, the UE determines a preferred resource group or a preferred resource pair, and reports an indication of the preferred resource group or the preferred resource pair.

[0235] In aspect 29, alone or in combination with one or more of aspects 25 to 28, each CSI-RS port spanning multiple CSI-RS resources is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

[0236] In the 30th aspect, alone or in combination with one or more of the 25th to 29th aspects, each CSI-RS resource is divided into at least two parts.

[0237] In the thirty-first aspect, alone or in combination with one or more of the twenty-fifth to thirtieth aspects, each CSI-RS resource is associated with a density corresponding to a frequency resource available for the CSI-RS.

[0238] In aspect 32, alone or in combination with one or more of aspects 25 to 31, the UE determines, for each CSI-RS port spanning multiple CSI-RS resources, a virtual CSI-RS port index based on a CSI-RS resource index corresponding to a CSI-RS resource including the CSI-RS port; determines that a PMI is mapped to the virtual CSI-RS port index; and / or calculates a channel quality indicator (CQI) based on the PMI and the virtual CSI-RS port index.

[0239] In the thirty-third aspect, alone or in combination with the first aspect, selecting any of the CSI-RS ports for the UE to report CSI comprises selecting any of the CSI-RS ports within a combined CSI-RS resource from a plurality of combined CSI-RS resources, wherein each combined CSI-RS resource comprises one or more component CSI-RS resources, and wherein each component CSI-RS resource comprises a plurality of CSI-RS ports.

[0240] In the thirty-fourth aspect, alone or in combination with the thirty-third aspect, the UE receives one or more resource mapping configurations for each combined CSI-RS resource, wherein each resource mapping configuration indicates a resource mapping for a corresponding CSI-RS component resource.

[0241] In the 35th aspect, alone or in combination with one or more of the 33rd and 34th aspects, the UE determines the index of the CSI-RS port based on an order corresponding to the one or more resource mapping configurations.

[0242] In aspect 36, alone or in combination with one or more of aspects 33 to 35, a first component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a first resource block (RB) set, and a second component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a second RB set, wherein the first RB set and the second RB set are the same or different.

[0243] In the thirty-seventh aspect, alone or in combination with the first aspect, selecting any CSI-RS port among the CSI-RS ports for the UE to report CSI includes: selecting any CSI-RS port among the CSI-RS ports within a CSI-RS resource from the multiple CSI-RS resources, wherein each CSI-RS resource includes multiple CSI-RS ports, and each port in each resource is mapped to multiple virtual CSI-RS ports.

[0244] In the thirty-eighth aspect, alone or in combination with the thirty-seventh aspect, each virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

[0245] In the thirty-ninth aspect, alone or in combination with one or more of the thirty-seventh and thirty-eighth aspects, virtual CSI-RS ports in the same group are mapped to the same CSI-RS port.

[0246] In the 40th aspect, alone or in combination with one or more of the 37th to 39th aspects, the virtual CSI-RS ports mapped to the same CSI-RS port are transmitted on different resource blocks.

[0247] In the forty-first aspect, alone or in combination with one or more of the thirty-seventh to fortieth aspects, virtual CSI-RS ports in the same group transmitted to the same set of resource blocks are mapped to different CSI-RS ports.

[0248] In aspect 42, alone or in combination with one or more of aspects 37 to 41, selecting any of the CSI-RS ports for the UE to report CSI includes: selecting any one or more virtual CSI-RS ports.

[0249] In aspect 43, alone or in combination with one or more of aspects 37 to 42, the UE determines a virtual CSI-RS port index for the virtual CSI-RS port based on the transmission of the virtual CSI-RS port on a resource block set and the corresponding CSI-RS port index; determines that the PMI is mapped to the virtual CSI-RS port index; and / or calculates a channel quality indicator (CQI) based on the PMI and the virtual CSI-RS port index.

[0250] In aspect 44, alone or in combination with one or more of aspects 37 to 43, the UE sends first signaling indicating a selected virtual CSI-RS port group; and second signaling indicating one or more selected virtual CSI-RS ports from the selected virtual CSI-RS port group.

[0251] In the forty-fifth aspect, either alone or in combination with the first aspect, the UE sends capability signaling indicating the UE's ability to select virtual CSI-RS ports across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports; or both.

[0252] In the forty-sixth aspect, either alone or in combination with the first aspect, the UE receives a configuration instructing the UE to select virtual CSI-RS ports across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports.

[0253] In a forty-seventh aspect, a method for wireless communication performed by a base station (BS) includes: sending a channel state information (CSI) request for a precoding matrix indicator (PMI) formed by a linear combination of multiple CSI reference signal (CSI-RS) ports selected by the UE to a user equipment (UE), wherein the port selection includes selecting any CSI-RS port from the multiple CSI-RS ports or selecting a CSI-RS port based on a grouping of the multiple CSI-RS ports; and receiving a CSI report from the UE including at least the port selection and a wideband linear combination coefficient.

[0254] In the forty-eighth aspect alone or in combination with the forty-seventh aspect, the port selection is polarization specific or polarization common.

[0255] In aspect 49, alone or in combination with one or more of aspects 47 and 48, each precoder used for the CSI-RS port is a spatial precoder associated with a specific spatial domain (SD) basis and frequency domain (FD) basis used to simulate the CSI-RS port; and different precoders are associated with different SD bases, different FD bases, or both.

[0256] In the fiftieth aspect, alone or in combination with one or more of aspects 47 to 49, the BS determines the grouping of the multiple CSI-RS ports by: determining a first portion of the multiple CSI-RS ports; and determining a second portion of the multiple CSI-RS ports.

[0257] In the fifty-first aspect, alone or in combination with one or more of aspects forty-seven to forty-seven, a first portion of the plurality of CSI-RS ports is associated with a first polarization; and a second portion of the plurality of CSI-RS ports is associated with a second polarization.

[0258] In aspect 52, alone or in combination with one or more of aspects 47 to 51, the BS determines the grouping of the multiple CSI-RS ports by: determining a first plurality of groups of CSI-RS ports in the first part; and determining a second plurality of groups of CSI-RS ports in the second part.

[0259] In the fifty-third aspect, alone or in combination with one or more of the forty-seventh to fifty-second aspects, the BS configures the number of CSI-RS port groups for the UE to report linear combination coefficients.

[0260] In the fifty-fourth aspect, alone or in combination with one or more of the forty-seventh to fifty-third aspects, the BS configures the number of CSI-RS ports within each CSI-RS port group to the UE for the UE to report linear combination coefficients.

[0261] In aspect 55, alone or in combination with one or more of aspects 47 to 54, the CSI report comprises one or more CSI-RS port group indices, one or more CSI-RS port indices, or both, for indicating the CSI-RS ports associated with the CSI report.

[0262] In aspect 56, alone or in combination with one or more of aspects 47 to 55, the CSI report comprises: one or more CSI-RS port group indexes for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port group indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port group indexes for the first plurality of CSI-RS ports; and / or one or more CSI-RS port indexes for a first CSI-RS port group, wherein the one or more CSI-RS port indexes for the remaining one or more CSI-RS port groups are determined based on the one or more CSI-RS port indexes for the first CSI-RS port group.

[0263] In aspect 57, alone or in combination with one or more of aspects 47 to 56, all CSI-RS ports within a specific group of the first and second multiple groups are associated with a common specific SD basis or FD basis, and within each of the groups, each specific CSI-RS port is associated with a specific one of the other of the SD basis or FD basis.

[0264] In aspect 58, alone or in combination with one or more of aspects 47 to 57, the BS determines the grouping of the CSI-RS ports by determining a plurality of CSI-RS resources, each CSI-RS resource including a first part and a second part of the CSI-RS port.

[0265] In the fifty-ninth aspect, alone or in combination with one or more of the forty-seventh to fifty-eighth aspects, the BS configures the number of CSI-RS resources for the UE to report linear combination coefficients.

[0266] In the sixtieth aspect, alone or in combination with one or more of the forty-seventh to fifty-ninth aspects, the BS configures, to the UE, the number of CSI-RS ports within each CSI-RS resource for the UE to report linear combination coefficients.

[0267] In the sixty-first aspect, alone or in combination with one or more of the forty-seventh to sixty-first aspects, the CSI report includes one or more resource indexes, one or more CSI-RS port indexes, or both, for indicating the CSI-RS ports associated with the CSI report.

[0268] In aspect 62, alone or in combination with one or more of aspects 47 to 61, the CSI report comprises: one or more CSI-RS resource indexes for a first plurality of CSI-RS ports, wherein the one or more CSI-RS resource indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS resource indexes for the first plurality of CSI-RS ports; one or more CSI-RS port indexes for a first CSI-RS resource, wherein the one or more CSI-RS port indexes for the remaining one or more CSI-RS resources are determined based on the one or more CSI-RS port indexes for the first CSI-RS resource; and / or one or more CSI-RS port indexes for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port indexes for the first plurality of CSI-RS ports.

[0269] In aspect 63, alone or in combination with one or more of aspects 47 to 62, each resource is associated with a specific SD basis or FD basis; and within each resource: each specific CSI-RS port in the first part of the CSI-RS ports is associated with a specific one of the other of the SD basis or the FD basis, and each specific CSI-RS port in the second part of the CSI-RS ports is associated with the specific one of the other of the SD basis or the FD basis.

[0270] In the sixty-fourth aspect, alone or in combination with one or more of the forty-seventh to sixty-third aspects, the BS configures, to the UE, a maximum number of CSI-RS ports per layer or per rank for the UE to report linear combination coefficients.

[0271] In aspect 65, alone or in combination with one or more of aspects 47 to 64, the CSI report comprises an indication of a number of non-zero CSI-RS ports associated with the CSI report that is equal to or less than a maximum number of configured CSI-RS ports.

[0272] In aspect 66, alone or in combination with one or more of aspects 47 to 65, the CSI report comprises an indication of non-zero CSI-RS ports associated with the CSI report that is equal to or less than a maximum number of configured CSI-RS ports.

[0273] In the sixty-seventh aspect, alone or in combination with one or more of the forty-seventh to sixty-sixth aspects, the BS configures a subset of the plurality of CSI-RS ports to the UE, and the UE may select up to the maximum number of CSI-RS ports per layer from the subset.

[0274] In the sixty-eighth aspect, alone or in combination with one or more of the forty-seventh to sixty-seventh aspects, the subset is configured to be rank-specific.

[0275] In the sixty-ninth aspect, alone or in combination with one or more of the forty-seventh to sixty-eighth aspects, the plurality of CSI-RS ports comprises more than 32 CSI-RS ports.

[0276] In the seventieth aspect, alone or in combination with one or more of the forty-seventh to sixty-ninth aspects, a frequency domain (FD) unit size is smaller than a subband.

[0277] In aspect seventy-one, alone or in combination with aspect forty-seven, the selection of the plurality of CSI-RS ports comprises selecting any of the CSI-RS ports across a plurality of CSI-RS resources, wherein each CSI-RS resource comprises a plurality of CSI-RS ports and is mapped to a virtual CSI-RS port.

[0278] In the seventy-second aspect, alone or in combination with the seventy-first aspect, the BS determines a resource grouping or a resource pairing based on the multiple CSI-RS resources, wherein the selection of the CSI-RS ports is performed across resources within the same resource grouping or the same resource pairing.

[0279] In the seventy-third aspect, alone or in combination with the seventy-first aspect, the BS determines resource grouping or resource pairing based on a reception configuration, based on an order of CSI-RS resources, or a combination thereof.

[0280] In the seventy-fourth aspect, alone or in combination with the seventy-first aspect, the BS determines a preferred resource group or a preferred resource pair; and receives an indication of the preferred resource group or the preferred resource pair from the UE.

[0281] In the seventy-fifth aspect, alone or in combination with the seventy-first aspect, the virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

[0282] In the seventy-sixth aspect, alone or in combination with the seventy-first aspect, each CSI-RS resource is divided into at least two parts.

[0283] In the seventy-seventh aspect, alone or in combination with one or more of the seventy-first to seventy-fifth aspects, each CSI-RS resource is associated with a density corresponding to the frequency resources available for the CSI-RS.

[0284] In aspect 78, alone or in combination with aspect 47, the selection of the multiple CSI-RS ports comprises selecting any CSI-RS port of the CSI-RS ports from one CSI-RS resource among a plurality of CSI-RS resources, wherein each CSI-RS resource comprises a plurality of CSI-RS ports and is mapped to a plurality of virtual CSI-RS ports.

[0285] In the seventy-ninth aspect, alone or in combination with the seventy-eighth aspect, each virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

[0286] In the 80th aspect alone or in combination with the 79th aspect, virtual CSI-RS ports in the same group are mapped to the same CSI-RS port.

[0287] In the eighty-first aspect alone or in combination with the eightieth aspect, virtual CSI-RS ports mapped to the same CSI-RS port are transmitted on different resource blocks.

[0288] In the 82nd aspect alone or in combination with the 78th aspect, virtual CSI-RS ports in the same group transmitted to the same set of resource blocks are mapped to different CSI-RS ports.

[0289] In the 83rd aspect alone or in combination with the 78th aspect, the selection of the plurality of CSI-RS ports comprises selecting any one or more virtual CSI-RS ports.

[0290] In the 84th aspect, alone or in combination with the 83rd aspect, the BS receives first signaling from the UE indicating a selected virtual CSI-RS port group; and receives second signaling from the UE indicating one or more selected virtual CSI-RS ports from the selected virtual CSI-RS port group.

[0291] In aspect 85, alone or in combination with aspect 78, a BS receives capability signaling from a UE indicating the UE's capability to select virtual CSI-RS ports across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports; or both.

[0292] In the 86th aspect, alone or in combination with the 47th aspect, the BS sends a configuration to the UE for instructing the UE to select a virtual CSI-RS port across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select a virtual CSI-RS port from within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports.

[0293] In aspect 87, alone or in combination with aspect 47, selecting the multiple CSI-RS ports for the UE to report CSI comprises selecting any CSI-RS port among the CSI-RS ports within a combined CSI-RS resource from a plurality of combined CSI-RS resources, wherein each combined CSI-RS resource comprises one or more component CSI-RS resources, and wherein each component CSI-RS resource comprises multiple CSI-RS ports.

[0294] In the 88th aspect, alone or in combination with the 87th aspect, the BS sends one or more resource mapping configurations for each combined CSI-RS resource, wherein each resource mapping configuration indicates a resource mapping for a corresponding CSI-RS component resource.

[0295] In the 89th aspect, alone or in combination with the 88th aspect, the index of the CSI-RS port is determined based on an order corresponding to the one or more resource mapping configurations.

[0296] In aspect 90, alone or in combination with aspect 87, a first component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a first set of resource blocks (RBs), and a second component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a second set of RBs, wherein the first set of RBs and the second set of RBs are the same or different.

[0297] In a ninety-first aspect, an apparatus for wireless communication comprises: a memory; and at least one processor coupled to the memory, and the at least one processor is configured to: select one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the apparatus to report CSI, wherein the port selection comprises: selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; calculating at least a wideband linear combination coefficient for the selected CSI-RS port; and providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a base station (BS) in a CSI report.

[0298] In a ninety-second aspect, an apparatus for wireless communication comprises: a memory; and at least one processor coupled to the memory, and the at least one processor is configured to: send a channel state information (CSI) request for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of CSI reference signal (CSI-RS) ports selected by the UE to a user equipment (UE), wherein the port selection comprises: selecting any CSI-RS port from the plurality of CSI-RS ports; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; and receive a CSI report from the UE comprising at least the port selection and a wideband linear combination coefficient.

[0299] In a ninety-third aspect, an apparatus for wireless communication comprises: a unit for selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the apparatus to report CSI, wherein the port selection comprises: selecting any CSI-RS port from the plurality of CSI-RS ports to report CSI; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; a unit for determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; a unit for calculating at least a wideband linear combination coefficient for the selected CSI-RS port; and a unit for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a base station (BS) in a CSI report.

[0300] In a ninety-fourth aspect, an apparatus for wireless communication comprises: means for sending a channel state information (CSI) request for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of CSI reference signal (CSI-RS) ports selected by the UE to a user equipment (UE), wherein the port selection comprises: selecting any CSI-RS port from the plurality of CSI-RS ports; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; and means for receiving a CSI report from the UE comprising at least the port selection and a wideband linear combination coefficient.

[0301] In a ninety-fifth aspect, a computer-readable medium having computer-executable code stored thereon for wireless communication comprises: code for selecting one or more channel state information reference signal (CSI-RS) ports among a plurality of CSI-RS ports for a user equipment (UE) to report CSI, wherein the port selection comprises: selecting any CSI-RS port among the plurality of CSI-RS ports to report CSI; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; code for determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; code for calculating at least a wideband linear combination coefficient for the selected CSI-RS port; and code for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficient to a base station (BS) in a CSI report.

[0302] In a ninety-sixth aspect, a computer-readable medium having computer-executable code stored thereon for wireless communication includes: code for sending a channel state information (CSI) request for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of CSI reference signal (CSI-RS) ports selected by the UE to a user equipment (UE), wherein the port selection includes: selecting any CSI-RS port from the plurality of CSI-RS ports; or selecting a CSI-RS port based on a grouping of the plurality of CSI-RS ports; and code for receiving a CSI report including at least the port selection and a wideband linear combination coefficient from the UE.

[0303] Additional Considerations

[0304] The techniques described herein can be used for various wireless communication technologies such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), Time Division Synchronous Code Division Multiple Access (TD-SCDMA), and other networks. The terms "network" and "system" are often used interchangeably. A CDMA network can implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, and the like. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95, and IS-856 standards. A TDMA network can implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and the like. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). LTE and LTE-A are versions of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). cdma2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). NR is an emerging wireless communication technology under development.

[0305] In 3GPP, the term "cell" can refer to the coverage area of a Node B (NB) and / or the NB subsystem serving that coverage area, depending on the context in which the term is used. In NR systems, the terms "cell" and "base station," next-generation Node B (gNB or gNodeB), access point (AP), distributed unit (DU), carrier, or transmit / receive point (TRP) can be used interchangeably. A base station (BS) can provide communication coverage for macro cells, pico cells, femto cells, and / or other types of cells. A macro cell can cover a relatively large geographic area (e.g., a radius of several kilometers) and can allow unrestricted access by UEs with service subscriptions. A pico cell can cover a relatively small geographic area and can allow unrestricted access by UEs with service subscriptions. A femto cell can cover a relatively small geographic area (e.g., a residence) and can allow restricted access by UEs associated with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in a residence, etc.). A base station for a macro cell can be referred to as a macro base station. A base station for a pico cell can be referred to as a pico base station. A BS for a femto cell may be referred to as a femto BS or a home BS.

[0306] A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, customer premises equipment (CPE), a cellular phone, a smartphone, 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 computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or apparatus, a biometric sensor / device, a wearable device (such as a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (e.g., a smart ring, a smart bracelet, etc.)), an entertainment device (e.g., a music device, a video device, a satellite radio unit, etc.), an in-vehicle component or sensor, a smart meter / sensor, an industrial manufacturing device, a global positioning system device, or any other suitable device configured to communicate via a wireless or wired medium. Some UEs may be considered machine type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., which can communicate with a base station, another device (e.g., a remote device), or some other entity. A wireless node can provide, for example, connectivity to a network (e.g., a wide area network such as the Internet or a cellular network) or to a network via a wired or wireless communication link. Some UEs can be considered Internet of Things (IoT) devices, which can be narrowband IoT (NB-IoT) devices.

[0307] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., BS) allocates resources for communication between some or all devices and apparatuses within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communications, the subordinate entities utilize the resources allocated by the scheduling entity. The base station is not the only entity that can be used as a scheduling entity. In some examples, a UE may be used as a scheduling entity, and resources for one or more subordinate entities (e.g., one or more other UEs) may be scheduled, and other UEs may utilize the resources scheduled by the UE to perform wireless communications. In some examples, a UE may be used as a scheduling entity in a peer-to-peer (P2P) network and / or in a mesh network. In the mesh network example, in addition to communicating with the scheduling entity, UEs may also communicate directly with each other.

[0308] In some examples, two or more slave entities (e.g., UEs) can communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, short-range services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh networks, and / or various other appropriate applications. Generally, a sidelink signal may refer to a signal transmitted from one slave entity (e.g., UE1) to another slave entity (e.g., UE2) without the need for the communication to be relayed by a scheduling entity (e.g., UE or BS), even though the scheduling entity may be used for scheduling and / or control purposes. In some examples, the sidelink signals may be transmitted using licensed spectrum (unlike wireless local area networks that typically use unlicensed spectrum).

[0309] The methods disclosed herein include one or more steps or actions for implementing the methods. Method steps and / or actions may be interchangeable with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0310] As used herein, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single members. For example, "at least one of a, b, or c" is intended to encompass a, b, c, ab, ac, bc, and abc, as well as any combination and multiples of the same element (e.g., aa, aaa, aab, aac, abb, acc, bb, bbb, bbc, cc, and ccc, or any other ordering of a, b, and c).

[0311] As used herein, the term "determining" includes a variety of actions. For example, "determining" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or another data structure), inferring, and the like. Furthermore, "determining" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Furthermore, "determining" may include resolving, selecting, choosing, establishing, and the like.

[0312] The foregoing description is provided to enable anyone skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Accordingly, the claims are not intended to be limited to the aspects shown herein, but rather to be given the full scope consistent with the text of the claims, wherein, unless specifically stated otherwise, reference to an element in the singular is not intended to mean "one and only one," but rather "one or more." Unless otherwise explicitly stated, the term "some" refers to one or more. All structural and functional equivalents of the elements of the various aspects described in this disclosure that are known or will become known to those skilled in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. In addition, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly stated in the claims. No claim element is to be interpreted under the provisions of 35 U.S.C. § 112(f) unless the element is explicitly stated using the phrase "means for..." or, in the case of a method claim, the element is stated using the phrase "step for..."

[0313] The various operations of the methods described above can be performed by any appropriate unit capable of performing the corresponding functions. The units may include various hardware and / or software components and / or modules, including but not limited to: circuits, application specific integrated circuits (ASICs) or processors. Generally, where there are operations shown in the figures, those operations may have corresponding counterpart functional module components with similar numbers.

[0314] The various illustrative logic blocks, modules, and circuits described in conjunction with the present disclosure may be implemented or performed using a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, a combination of one or more microprocessors and a DSP core, or any other such configuration.

[0315] If implemented in hardware, an example hardware configuration may include a processing system in a wireless node. The processing system may be implemented using a bus architecture. Depending on the specific application and overall design constraints of the processing system, the bus may include any number of interconnecting buses and bridges. The bus may link together various circuits including a processor, a machine-readable medium, and a bus interface. The bus interface may be used to connect a network adapter, etc., to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the user terminal 120 (see Figure 1 ), a user interface (e.g., a keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, etc., which are well known in the art and therefore will not be described further. The processor may be implemented using one or more general and / or special purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuits that can execute software. Those skilled in the art will recognize that how to best implement the functionality described for the processing system depends on the specific application and the overall design constraints imposed on the entire system.

[0316] If implemented in software, the functionality may be stored as one or more instructions or codes on or transmitted via a computer-readable medium. Whether referred to as software, firmware, middleware, microcode, hardware description language, or other terms, software should be broadly interpreted to mean instructions, data, or any combination thereof. Computer-readable media includes both computer storage media and communication media, including any medium that facilitates the transfer of computer programs from one location to another. The processor may be responsible for managing the bus and general processing, including executing software modules stored on a machine-readable storage medium. The computer-readable storage medium may be coupled to the processor so that the processor can read information from and write information to the storage medium. Alternatively, the storage medium may be integrated into the processor. For example, the machine-readable medium may include a transmission line, a carrier modulated by data, and / or a computer-readable storage medium having instructions stored thereon, separate from the wireless node, all of which may be accessed by the processor via a bus interface. Alternatively, or in addition, the machine-readable medium or any portion thereof may be integrated into the processor, for example, in the form of a cache and / or general register file. For example, examples of machine-readable storage media may include RAM (random access memory), flash memory, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage media, or any combination thereof. The machine-readable medium may be embodied in a computer program product.

[0317] A software module may include a single instruction or many instructions and may be distributed across several different code segments, among different programs, and across multiple storage media. A computer-readable medium may include multiple software modules. A software module includes instructions that, when executed by a device such as a processor, cause a processing system to perform various functions. A software module may include a sending module and a receiving module. Each software module may be located in a single storage device or distributed across multiple storage devices. For example, when a triggering event occurs, a software module may be loaded from a hard drive into RAM. During execution of the software module, the processor may load some of the instructions into a cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. It will be understood that when reference is made to the functions of a software module below, such functions are implemented by the processor when executing instructions from that software module.

[0318] Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and optical disc. Optical disks, where magnetic disks typically reproduce data magnetically, and optical disks use lasers to reproduce data optically. Thus, in some aspects, computer-readable media may include non-transitory computer-readable media (e.g., tangible media). Furthermore, for other aspects, computer-readable media may include transitory computer-readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0319] Thus, certain aspects may include a computer program product for performing the operations presented herein. For example, such a computer program product may include a computer-readable medium having instructions stored (and / or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For example, a computer program product for performing the operations described herein and in Figure 7 and / or Figure 8 The operation instructions are shown in .

[0320] In addition, it should be appreciated that the modules and / or other appropriate units for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by the user terminal and / or base station where applicable. For example, such a device can be coupled to a server to facilitate the transmission of the units for performing the methods described herein. Alternatively, the various methods described herein can be provided via a storage unit (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or a floppy disk, etc.) so that the user terminal and / or base station can obtain the various methods when the storage unit is coupled to or provided to the device. In addition, any other appropriate technology for providing the methods and techniques described herein to a device can be utilized.

[0321] It is to be understood that the claims are not limited to the precise configuration and components shown above, and that various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A method for wireless communication performed by a user equipment (UE), comprising: selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the UE to report CSI, wherein the port selection comprises selecting the CSI-RS ports based on a grouping of the plurality of CSI-RS ports; determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; calculating at least wideband linear combination coefficients for the selected CSI-RS port; and Provide the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to the base station (BS) in a CSI report, The selecting the one or more CSI-RS ports for the UE to report CSI includes: determining a grouping of the plurality of CSI-RS ports; and selecting the one or more CSI-RS ports based at least in part on the grouping; and The determining of the grouping of the multiple CSI-RS ports includes: determining a first plurality of groups of the CSI-RS ports in a first portion; and A second plurality of groups of the CSI-RS ports in a second portion is determined.

2. The method according to claim 1, wherein The wideband linear combination coefficients are calculated across all frequency domain (FD) units for each selected CSI-RS port.

3. The method according to claim 1, wherein The port selection is either polarization specific or polarization common.

4. The method according to claim 1, wherein: The first portion of the plurality of CSI-RS ports is associated with a first polarization; and The second portion of the plurality of CSI-RS ports is associated with a second polarization.

5. The method according to claim 1, wherein: All CSI-RS ports within a particular group of the first and second pluralities of groups are associated with a common particular spatial domain (SD) basis or frequency domain (FD) basis, and Within each of the groups, each specific CSI-RS port is associated with a specific one of the SD basis or the other of the FD basis.

6. The method according to claim 1, further comprising: A configuration of the number of CSI-RS port groups for the UE to report linear combination coefficients is received from the BS, wherein the selecting includes selecting CSI-RS ports from up to the configured number of CSI-RS port groups.

7. The method according to claim 6, further comprising: A configuration of a number of CSI-RS ports within each CSI-RS port group for the UE to report linear combination coefficients is received from the base station, wherein the selecting includes selecting up to the configured number of CSI-RS ports from each of the selected CSI-RS port groups.

8. The method according to claim 1, wherein Providing the selected one or more CSI-RS ports includes indicating one or more CSI-RS port group indices, one or more CSI-RS port indices, or both.

9. The method according to claim 8, wherein Providing the selected one or more CSI-RS ports further includes at least one of the following operations: providing one or more CSI-RS port group indexes for a first plurality of CSI-RS ports, wherein the one or more CSI-RS port group indexes for a second plurality of CSI-RS ports are determined based on the one or more CSI-RS port group indexes for the first plurality of CSI-RS ports; and One or more CSI-RS port indexes are provided for a first CSI-RS port group, wherein one or more CSI-RS port indexes for the remaining one or more CSI-RS port groups are determined based on the one or more CSI-RS port indexes for the first CSI-RS port group.

10. The method according to claim 1, wherein Determining the grouping of the multiple CSI-RS ports includes: determining a plurality of CSI-RS resources, each CSI-RS resource comprising a first portion and a second portion of the CSI-RS port; and receiving, from a BS, a configuration of the number of CSI-RS resources for the UE to report linear combination coefficients; The selecting includes selecting a CSI-RS port from up to a configured number of CSI-RS resources.

11. The method according to claim 10, wherein: All CSI-RS ports within a specific CSI-RS resource are associated with a specific spatial domain (SD) basis or frequency domain (FD) basis; and Within each CSI-RS resource: Each particular CSI-RS port in the first portion of CSI-RS ports is associated with a particular one of an SD basis or an FD basis; and Each specific CSI-RS port in the second portion of CSI-RS ports is associated with the specific one of the other one of the SD basis or the FD basis.

12. The method according to claim 10, further comprising: A configuration of a number of CSI-RS ports within each CSI-RS resource for the UE to report linear combination coefficients is received from the base station, wherein the selecting includes selecting up to the configured number of CSI-RS ports from each of the selected CSI-RS resources.

13. The method according to claim 10, wherein: Providing the selected one or more CSI-RS ports includes indicating one or more CSI-RS resource indices, one or more CSI-RS port indices, or both for indicating the selected CSI-RS ports associated with the CSI report.

14. The method according to claim 11, wherein Providing the selected one or more CSI-RS ports further includes at least one of the following operations: providing one or more CSI-RS resource indexes for a first plurality of CSI-RS ports, wherein the one or more CSI-RS resource indexes for a second plurality of CSI-RS ports are determined based on the one or more CSI-RS resource indexes for the first plurality of CSI-RS ports; providing one or more CSI-RS port indexes for a first CSI-RS resource, wherein one or more CSI-RS port indexes for the remaining one or more CSI-RS resources are determined based on the one or more CSI-RS port indexes for the first CSI-RS resource; and One or more CSI-RS port indexes are provided for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port indexes for the first plurality of CSI-RS ports.

15. The method according to claim 1, further comprising: A configuration of a maximum number of CSI-RS ports per layer or per rank for the UE to report linear combination coefficients is received from the BS.

16. The method according to claim 15, further comprising: An indication of a number of non-zero CSI-RS ports associated with the CSI report that is equal to or less than a configured maximum number of CSI-RS ports is reported to the BS.

17. The method according to claim 15, further comprising: An indication of non-zero CSI-RS ports associated with the CSI report that is equal to or less than a configured maximum number of CSI-RS ports is reported to the BS.

18. The method according to claim 15, further comprising: A configuration of a subset of the plurality of CSI-RS ports is received from the BS, wherein the selecting the one or more CSI-RS ports for the UE to report CSI comprises: selecting a CSI-RS port from the subset of CSI-RS ports.

19. The method according to claim 18, wherein The subsets are configured to be rank specific.

20. The method according to claim 1, wherein The plurality of CSI-RS ports includes more than 32 CSI-RS ports.

21. The method according to claim 1, wherein The frequency domain (FD) unit size is smaller than the subband.

22. The method according to claim 1, wherein Selecting any CSI-RS port among the multiple CSI-RS ports for the UE to report the CSI includes: Any of the CSI-RS ports is selected across a plurality of CSI-RS resources, wherein each CSI-RS resource includes a plurality of CSI-RS ports.

23. The method according to claim 22, further comprising: A resource grouping or resource pairing is determined based on the multiple CSI-RS resources, wherein the CSI-RS ports are selected across resources within the same resource grouping or the same resource pairing.

24. The method according to claim 23, wherein Determining the resource grouping or resource pairing is based on a configuration received from the BS, based on an order of the CSI-RS resources, or a combination thereof.

25. The method of claim 23, further comprising: Determining a preferred resource group or preferred resource pair; and An indication of the preferred resource group or the preferred resource pair is reported.

26. The method according to claim 22, wherein Each CSI-RS port spanning multiple CSI-RS resources is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

27. The method according to claim 22, wherein Each CSI-RS resource is divided into at least two parts.

28. The method according to claim 22, wherein Each CSI-RS resource is associated with a density corresponding to frequency resources available for CSI-RS.

29. The method of claim 22, further comprising: determining, for each CSI-RS port spanning a plurality of CSI-RS resources, a virtual CSI-RS port index based on a CSI-RS resource index corresponding to a CSI-RS resource including the CSI-RS port; Determining that the PMI is mapped to the virtual CSI-RS port index; and A channel quality indicator (CQI) is calculated based on the PMI and the virtual CSI-RS port index.

30. The method of claim 1, wherein Selecting any CSI-RS port among the multiple CSI-RS ports for the UE to report the CSI includes: Any of the CSI-RS ports is selected from a combined CSI-RS resource of a plurality of combined CSI-RS resources, wherein each combined CSI-RS resource includes one or more component CSI-RS resources, and wherein each component CSI-RS resource includes a plurality of CSI-RS ports.

31. The method of claim 30, further comprising: One or more resource mapping configurations are received for each combined CSI-RS resource, wherein each resource mapping configuration indicates a resource mapping for a corresponding CSI-RS component resource.

32. The method of claim 31 , further comprising: The index of the CSI-RS port is determined based on an order corresponding to the one or more resource mapping configurations.

33. The method according to claim 30, wherein A first component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a first resource block (RB) set, and a second component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a second RB set, wherein the first RB set and the second RB set are the same or different.

34. The method of claim 1, wherein Selecting any CSI-RS port among the multiple CSI-RS ports for the UE to report the CSI includes: Any of the CSI-RS ports is selected from a CSI-RS resource among a plurality of CSI-RS resources, wherein each CSI-RS resource includes a plurality of CSI-RS ports and each port in each resource is mapped to a plurality of virtual CSI-RS ports.

35. The method according to claim 34, wherein Each virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

36. The method of claim 34, wherein: The virtual CSI-RS ports in the same group are mapped to the same CSI-RS port.

37. The method according to claim 36, wherein The virtual CSI-RS ports mapped to the same CSI-RS port are transmitted on different resource blocks.

38. The method of claim 34, wherein: The virtual CSI-RS ports in the same group sent to the same resource block set are mapped to different CSI-RS ports.

39. The method of claim 34, wherein: Selecting any CSI-RS port from the plurality of CSI-RS ports for the UE to report the CSI includes: selecting any one or more virtual CSI-RS ports.

40. The method of claim 34, further comprising: determining a virtual CSI-RS port index for the virtual CSI-RS port based on transmission of the virtual CSI-RS port on a set of resource blocks and a corresponding CSI-RS port index; Determining that the PMI is mapped to the virtual CSI-RS port index; and A channel quality indicator (CQI) is calculated based on the PMI and the virtual CSI-RS port index.

41. The method of claim 34, further comprising: Sending first signaling for indicating a selected virtual CSI-RS port group; as well as Second signaling indicating one or more selected virtual CSI-RS ports from within the selected virtual CSI-RS port group is sent.

42. The method of claim 1, further comprising: and transmitting capability signaling indicating the UE's capability to select virtual CSI-RS ports across CSI-RS resources, where each CSI-RS port in each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, where each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports; or both.

43. The method of claim 1, further comprising: A configuration is received to instruct the UE to select virtual CSI-RS ports across CSI-RS resources, where each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, where each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports.

44. A method for wireless communication performed by a base station (BS), comprising: Sending a CSI request to a user equipment (UE) for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of channel state information (CSI) reference signal (CSI-RS) ports selected by the UE, wherein the port selection comprises: selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; receiving a CSI report from the UE including at least the port selection and wideband linear combination coefficients; and The grouping of the multiple CSI-RS ports is determined by the following operations: determining a first portion of the plurality of CSI-RS ports; and Determine a second portion of the plurality of CSI-RS ports Wherein, determining the grouping of the multiple CSI-RS ports includes: determining a first plurality of groups of CSI-RS ports in the first portion; and A second plurality of groups of CSI-RS ports in the second portion is determined.

45. The method of claim 44, wherein: The port selection is either polarization specific or polarization common.

46. The method of claim 44, wherein: Each precoder for the CSI-RS port is a spatial precoder associated with a particular spatial domain (SD) basis and frequency domain (FD) basis used to emulate the CSI-RS port; and Different precoders are associated with different SD bases, different FD bases, or both.

47. The method of claim 44, wherein: The first portion of the plurality of CSI-RS ports is associated with a first polarization; and The second portion of the plurality of CSI-RS ports is associated with a second polarization.

48. The method of claim 44, further comprising: The number of CSI-RS port groups for the UE to report linear combination coefficients is configured for the UE.

49. The method of claim 44, further comprising: The number of CSI-RS ports in each CSI-RS port group for the UE to report linear combination coefficients is configured for the UE.

50. The method of claim 44, wherein The CSI report includes: one or more CSI-RS port group indexes, one or more CSI-RS port indexes, or both for indicating CSI-RS ports associated with the CSI report.

51. The method of claim 50, wherein the CSI report comprises at least one of: One or more CSI-RS port group indexes for a first plurality of CSI-RS ports, wherein One or more CSI-RS port group indexes for a second plurality of CSI-RS ports are determined based on the one or more CSI-RS port group indexes for the first plurality of CSI-RS ports; as well as One or more CSI-RS port indexes for a first CSI-RS port group, wherein one or more CSI-RS port indexes for the remaining one or more CSI-RS port groups are determined based on the one or more CSI-RS port indexes for the first CSI-RS port group.

52. The method of claim 44, wherein All CSI-RS ports within a specific group in the first plurality of groups and the second plurality of groups are associated with a common specific SD basis or FD basis, and Within each of the groups, each specific CSI-RS port is associated with a specific one of the SD basis or the other of the FD basis.

53. The method of claim 44, further comprising determining the grouping of the CSI-RS ports by: A plurality of CSI-RS resources are determined, each CSI-RS resource including a first portion and a second portion of the CSI-RS port.

54. The method of claim 53, further comprising: The number of the CSI-RS resources for the UE to report linear combination coefficients is configured for the UE.

55. The method of claim 53, further comprising: The number of the CSI-RS ports in each CSI-RS resource for the UE to report linear combination coefficients is configured for the UE.

56. The method of claim 53, wherein The CSI report includes one or more resource indexes, one or more CSI-RS port indexes, or both for indicating CSI-RS ports associated with the CSI report.

57. The method of claim 56, wherein The CSI report includes at least one of the following: one or more CSI-RS resource indexes for a first plurality of CSI-RS ports, wherein the one or more CSI-RS resource indexes for a second plurality of CSI-RS ports are determined based on the one or more CSI-RS resource indexes for the first plurality of CSI-RS ports; one or more CSI-RS port indexes for a first CSI-RS resource, wherein the one or more CSI-RS port indexes for the remaining one or more CSI-RS resources are determined based on the one or more CSI-RS port indexes for the first CSI-RS resource; and One or more CSI-RS port indexes for the first plurality of CSI-RS ports, wherein the one or more CSI-RS port indexes for the second plurality of CSI-RS ports are determined based on the one or more CSI-RS port indexes for the first plurality of CSI-RS ports.

58. The method of claim 44, wherein: Each resource is associated with a specific SD base or FD base; and Within each resource: Each particular CSI-RS port in the first portion of CSI-RS ports is associated with a particular one of an SD basis or an FD basis; and Each specific CSI-RS port in the second portion of CSI-RS ports is associated with the specific one of the other one of the SD basis or the FD basis.

59. The method of claim 44, further comprising: The UE is configured with a maximum number of CSI-RS ports per layer or per rank for the UE to report linear combination coefficients.

60. The method of claim 59, wherein The CSI report includes an indication of a number of non-zero CSI-RS ports associated with the CSI report that is equal to or smaller than the maximum number of CSI-RS ports.

61. The method of claim 59, wherein: The CSI report includes an indication of non-zero CSI-RS ports associated with the CSI report that is equal to or smaller than a maximum number of CSI-RS ports.

62. The method of claim 59, further comprising: The UE is configured with a subset of the plurality of CSI-RS ports, from which the UE may select up to the maximum number of CSI-RS ports per layer.

63. The method of claim 62, wherein: The subsets are configured to be rank specific.

64. The method of claim 44, wherein: The plurality of CSI-RS ports includes more than 32 CSI-RS ports.

65. The method of claim 44, wherein The frequency domain (FD) unit size is smaller than the subband.

66. The method of claim 44, wherein The selecting of the plurality of CSI-RS ports includes selecting any CSI-RS port among the CSI-RS ports across a plurality of CSI-RS resources, wherein each CSI-RS resource includes a plurality of CSI-RS ports and is mapped to a virtual CSI-RS port.

67. The method of claim 66, further comprising: A resource grouping or resource pairing is determined based on the multiple CSI-RS resources, wherein the CSI-RS ports are selected across resources within the same resource grouping or the same resource pairing.

68. The method of claim 67, wherein Determining the resource grouping or the resource pairing is based on a received configuration, based on an order of the CSI-RS resources, or a combination thereof.

69. The method of claim 66, further comprising: Determining a preferred resource group or preferred resource pair; and An indication of a preferred resource group or preferred resource pair is received from the UE.

70. The method of claim 66, wherein The virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

71. The method of claim 66, wherein Each CSI-RS resource is divided into at least two parts.

72. The method of claim 70, wherein Each CSI-RS resource is associated with a density corresponding to frequency resources available for CSI-RS.

73. The method of claim 44, wherein: The selecting of the plurality of CSI-RS ports includes selecting any of the CSI-RS ports from within a CSI-RS resource among a plurality of CSI-RS resources, wherein each CSI-RS resource includes a plurality of CSI-RS ports and is mapped to a plurality of virtual CSI-RS ports.

74. The method of claim 73, wherein Each virtual CSI-RS port is associated with a pair of spatial domain (SD) basis and frequency domain (FD) basis.

75. The method of claim 73, wherein Virtual CSI-RS ports in the same group are mapped to the same CSI-RS port.

76. The method of claim 75, wherein The virtual CSI-RS ports mapped to the same CSI-RS port are transmitted on different resource blocks.

77. The method of claim 73, wherein Virtual CSI-RS ports in the same group sent to the same set of resource blocks are mapped to different CSI-RS ports.

78. The method of claim 73, wherein The selecting of the plurality of CSI-RS ports includes selecting any one or more virtual CSI-RS ports.

79. The method of claim 78, further comprising: receiving, from the UE, first signaling indicating a selected virtual CSI-RS port group; as well as Second signaling is received from the UE indicating one or more selected virtual CSI-RS ports from within the selected virtual CSI-RS port group.

80. The method of claim 44, further comprising: Capability signaling is received from the UE indicating the capability of the UE to select virtual CSI-RS ports across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports; or both.

81. The method of claim 44, further comprising: A configuration is sent to the UE to instruct the UE to select virtual CSI-RS ports across CSI-RS resources, wherein each CSI-RS port of each CSI-RS resource corresponds to one virtual CSI-RS port; or to select virtual CSI-RS ports from within a single CSI-RS resource, wherein each CSI-RS port in the CSI-RS resource corresponds to multiple virtual CSI-RS ports.

82. The method of claim 44, wherein Selecting the multiple CSI-RS ports for the UE to report the CSI includes: Any of the CSI-RS ports is selected from a combined CSI-RS resource among a plurality of combined CSI-RS resources, wherein each combined CSI-RS resource includes one or more component CSI-RS resources, and wherein each component CSI-RS resource includes a plurality of CSI-RS ports.

83. The method of claim 82, further comprising: One or more resource mapping configurations for each combined CSI-RS resource are sent, where each resource mapping configuration indicates a resource mapping for a corresponding CSI-RS component resource.

84. The method of claim 83, wherein The index of the CSI-RS port is determined based on an order corresponding to the one or more resource mapping configurations.

85. The method of claim 82, wherein A first component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a first resource block (RB) set, and a second component CSI-RS resource of the one or more component CSI-RS resources is transmitted on a second RB set, wherein the first RB set and the second RB set are the same or different.

86. An apparatus for wireless communication, comprising: Memory; as well as at least one processor coupled to the memory, and the at least one processor configured to: Selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the apparatus to report CSI, wherein the port selection comprises: selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; calculating at least wideband linear combination coefficients for the selected CSI-RS port; and Provide the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to the base station (BS) in a CSI report, The at least one processor configured to select the one or more CSI-RS ports for the apparatus to report CSI is further configured to: determining a grouping of the plurality of CSI-RS ports; and selecting the one or more CSI-RS ports based at least in part on the grouping; and The at least one processor configured to determine the grouping of the multiple CSI-RS ports is further configured to: determining a first plurality of groups of the CSI-RS ports in a first portion; and A second plurality of groups of the CSI-RS ports in a second portion is determined.

87. An apparatus for wireless communication, comprising: Memory; as well as at least one processor coupled to the memory, and the at least one processor configured to: Sending a CSI request to a user equipment (UE) for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of channel state information (CSI) reference signal (CSI-RS) ports selected by the UE, wherein the port selection includes selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; receiving a CSI report from the UE including at least the port selection and wideband linear combination coefficients; and The grouping of the multiple CSI-RS ports is determined by the following operations: determining a first portion of the plurality of CSI-RS ports; and Determine a second portion of the plurality of CSI-RS ports The at least one processor configured to determine the grouping of the multiple CSI-RS ports is further configured to: determining a first plurality of groups of CSI-RS ports in the first portion; and A second plurality of groups of CSI-RS ports in the second portion is determined.

88. An apparatus for wireless communication, comprising: means for selecting one or more channel state information reference signal (CSI-RS) ports from a plurality of CSI-RS ports for the apparatus to report CSI, wherein the port selection comprises selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; means for determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; means for calculating at least wideband linear combination coefficients for the selected CSI-RS port; and means for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to a base station (BS) in a CSI report, The unit for selecting the one or more CSI-RS ports for the apparatus to report CSI includes: means for determining a grouping of the plurality of CSI-RS ports; and means for selecting the one or more CSI-RS ports based at least in part on the grouping; and The unit for determining the grouping of the multiple CSI-RS ports includes: means for determining a first plurality of groups of the CSI-RS ports in a first portion; and Means for determining a second plurality of groups of the CSI-RS ports in a second portion.

89. An apparatus for wireless communication, comprising: Means for sending to a user equipment (UE) a CSI request for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of channel state information (CSI) reference signal (CSI-RS) ports selected by the UE, wherein the port selection comprises selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; and means for receiving a CSI report including at least the port selection and wideband linear combination coefficients from the UE; and The unit is configured to determine the grouping of the plurality of CSI-RS ports by: determining a first portion of the plurality of CSI-RS ports; and determining a second portion of the plurality of CSI-RS ports, The unit for determining the grouping of the multiple CSI-RS ports includes: means for determining a first plurality of groups of CSI-RS ports in the first portion; and Means for determining a second plurality of groups of CSI-RS ports in the second portion.

90. A computer-readable medium having stored thereon computer-executable code for wireless communication, comprising: Code for selecting one or more channel state information reference signal (CSI-RS) ports among a plurality of CSI-RS ports for a user equipment (UE) to report CSI, wherein the port selection includes selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; code for determining a precoding matrix indicator (PMI) formed by a linear combination of the one or more selected CSI-RS ports; code for calculating at least wideband linear combination coefficients for the selected CSI-RS port; and code for providing the selected one or more CSI-RS ports and the calculated wideband linear combination coefficients to a base station (BS) in a CSI report, The code for selecting the one or more CSI-RS ports for the UE to report CSI includes: code for determining grouping of the plurality of CSI-RS ports; and code for selecting the one or more CSI-RS ports based at least in part on the grouping; and The code for determining the grouping of the multiple CSI-RS ports includes: code for determining a first plurality of groups of the CSI-RS ports in a first portion; and Code for determining a second plurality of groups of the CSI-RS ports in a second portion.

91. A computer-readable medium having stored thereon computer-executable code for wireless communication, comprising: Code for transmitting to a user equipment (UE) a CSI request for a precoding matrix indicator (PMI) formed by a linear combination of a plurality of channel state information (CSI) reference signal (CSI-RS) ports selected by the UE, wherein the port selection includes selecting a CSI-RS port based on the grouping of the plurality of CSI-RS ports; and code for receiving a CSI report from the UE including at least the port selection and wideband linear combination coefficients; and Code for determining a grouping of the plurality of CSI-RS ports by: determining a first portion of the plurality of CSI-RS ports; and determining a second portion of the plurality of CSI-RS ports, The code for determining the grouping of the multiple CSI-RS ports includes: code for determining a first plurality of groups of CSI-RS ports in the first portion; and Code for determining a second plurality of groups of CSI-RS ports in the second portion.

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