WO2018103077A1

WO2018103077A1 - Csi feedback for high resolution beam combination codebook

Info

Publication number: WO2018103077A1
Application number: PCT/CN2016/109242
Authority: WO
Inventors: Chao Wei; Bo Chen; Liangming WU; Jilei Hou
Original assignee: Qualcomm Incorporated
Priority date: 2016-12-09
Filing date: 2016-12-09
Publication date: 2018-06-14
Also published as: WO2018103741A1

Abstract

Certain aspects of the present disclosure provide techniques for transmitting CSI feedback for high resolution beam combination codebooks in an efficient manner.

Description

CSI FEEDBACK FOR HIGH RESOLUTION BEAM COMBINATION CODEBOOK

INTRODUCTION

Aspects of the present disclosure related generally to wireless communications systems, and more particularly, to techniques for reporting channel state information.

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power) . Examples of such multiple-access technologies include Long Term Evolution (LTE) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

A wireless communication network may include a number of Node Bs that can support communication for a number of user equipments (UEs) . A UE may communicate with a Node B via the downlink and uplink. The downlink (or forward link) refers to the communication link from the Node B to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the Node B.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is new radio (NR, e.g., 5G radio access) . NR is a set of enhancements to the LTE mobile standard promulgated by Third Generation Partnership Project (3GPP) . It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved communications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide a method for wireless communications by a user equipment (UE) . The method generally includes receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports, generating CSI feedback, based on the CSI-RS and subsampling of a first codebook, and reporting the generated CSI feedback.

Certain aspects of the present disclosure provide a method for wireless communications by a user equipment (UE) . The method generally includes receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports, generating CSI feedback, based on the CSI-RS, selecting a physical uplink control channel (PUCCH) format for CSI feedback with precoding matrix indicator (PMI) based, at least in part, on a payload size of the CSI feedback, and reporting the CSI feedback using a PUCCH of the selected format.

Certain aspects of the present disclosure provide a method for wireless communications by a user equipment (UE) . The method generally includes determining a restriction on a maximum number of resource blocks (RBs) available for uplink control information in a physical uplink shared channel (PUSCH) based, at least in part, based on a type of channel station information (CSI) reporting and reporting CSI feedback in accordance with the determination.

In an aspect, a method for wireless communications is provided. The method may be performed, for example, by a user equipment. The method generally includes encoding a reference channel state information (CSI) for transmission in a first slot, encoding a first differential CSI from the reference CSI for transmission in a second slot, and transmitting the reference CSI and the first differential CSI to a base station (BS) in a plurality of slots including the first slot and the second slot.

In an aspect, a method for wireless communications is provided. The method may be performed, for example, by a base station. The method generally includes receiving a reference channel state information (CSI) from a user equipment (UE) in a first slot, receiving, from the UE, a first differential CSI from the reference CSI in a second slot, and computing a first CSI based on the reference CSI and the first differential CSI.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, according to aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating an example downlink frame structure in a telecommunications system, according to aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example uplink frame structure in a telecommunications system, according to aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of an example Node B and user equipment (UE) , according to aspects of the present disclosure.

FIG. 5 is a diagram illustrating an example radio protocol architecture for the user and control planes, according to aspects of the present disclosure.

FIG. 6 illustrates an exemplary antenna array, according to aspects of the present disclosure.

FIGs. 7, 8, and 9 illustrate example CSI-RS configurations, according to aspects of the present disclosure.

FIG. 10 illustrates example CSI-RS generation.

FIG. 11 illustrates example CSI-RS payload size.

FIG. 12 illustrates example operations for wireless communications by a base station, according to aspects of the present disclosure.

FIG. 13 illustrates example CSI-RS generation, in accordance with aspects of the present disclosure.

FIG. 14 illustrates example CSI-RS payload size, in accordance with aspects of the present disclosure.

FIG. 15 illustrates example operations for wireless communications by a base station, according to aspects of the present disclosure.

FIG. 16 illustrates how PUCCH formats may be selected based on CSI-RS payload size, in accordance with aspects of the present disclosure.

FIG. 17 illustrates how CSI-RS reporting resources may be indicated, in accordance with aspects of the present disclosure.

FIG. 18 illustrates example operations for wireless communications by a base station, according to aspects of the present disclosure.

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

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer program products for new radio (NR) (new radio access technology) cell measurement. New radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA) -based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP) ) . NR may include Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. 80 MHz beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g. 60 GHz) , massive MTC (mMTC) targeting non-backward compatible MTC techniques, and mission critical targeting ultra reliable low latency communications (URLLC) . For these general topics, different techniques are considered, such as coding, low-density parity check (LDPC) , and polar. NR cell may refer to a cell operating according to the new air interface or fixed transport layer. A NR Node B (e.g., 5G Node B) may correspond to one or multiple transmission reception points (TRPs) .

NR cells can be configured as access cell (ACells) or data only cells (DCells) . For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals—in some case cases DCells may transmit SS. TRPs may transmit downlink signals to UEs indicating the cell type. Based on the cell type indication, the UE may communicate with the TRP. For example, the UE may determine TRPs to consider for cell selection, access, handover, and/or measurement based on the indicated cell type.

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

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.

Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting and the scope of the disclosure is being defined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wireless communication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology 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, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . NR is an emerging wireless communications technology under development in conjunction with the 5G Technology Forum (5GTF) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases 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) . The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

EXAMPLE WIRELESS COMMUNICATIONS SYSTEM

FIG. 1 illustrates an example wireless network 100 in which aspects of the present disclosure may be performed. For example, the wireless network may be new radio or 5G network. UEs 120 may configured to perform the operations 1200 discussed in more detail below for determining a cell type of a cell and communicating with the cell based on the determination. Node B 110 may comprise a transmission reception point (TRP) configured to perform the operations 1300 discussed in more detail below for identifying the cell type and providing an indication of the cell type to the UE 120. The NR network may include the central unit. The new radio network 100 may comprise a central unit 140 configured to perform the operations 1400 discussed in more detail below for determining cell types for TRPs and configuring the TRPs with the cell types. According to certain aspects, the UEs 120, Node B 110 (TRP) , and central unit 140 may be configured to perform operations related to measurement configuration, measurement reference signal transmission, monitoring, detection, measurement, and measurement reporting, which are described in greater detail below.

The system illustrated in FIG. 1 may be, for example, a long term evolution (LTE) network. The wireless network 100 may include a number of Node Bs (e.g., evolved NodeBs (eNB) , 5G Node B, etc. ) 110 and other network entities. A Node B may be a station that communicates with the UEs and may also be referred to as a base station, an access point, etc. A Node B and 5G Node B are other examples of stations that communicate with the UEs.

Each Node B 110 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a Node B and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used.

A Node B may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) , UEs for users in the home, etc. ) . A Node B for a macro cell may be referred to as a macro Node B. A Node B for a pico cell may be referred to as a pico Node B. A Node B for a femto cell may be referred to as a femto Node B or a home Node B. In the example shown in FIG. 1, the

Node Bs

110a, 110b and 110c may be macro Node Bs for the

macro cells

102a, 102b and 102c, respectively. The Node B 110x may be a pico Node B for a pico cell 102x. The Node Bs 110y and 110z may be femto Node Bs for the

femto cells

102y and 102z, respectively. A Node B may support one or multiple (e.g., three) cells.

The wireless network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., a Node B or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or a Node B) . A relay station may also be a UE that relays transmissions for other UEs. In the example shown in FIG. 1, a relay station 110r may communicate with the Node B 110a and a UE 120r in order to facilitate communication between the Node B 110a and the UE 120r. A relay station may also be referred to as a relay Node B, a relay, etc.

The wireless network 100 may be a heterogeneous network that includes Node Bs of different types, e.g., macro Node Bs, pico Node Bs, femto Node Bs, relays, transmission reception points (TRPs) , etc. These different types of Node Bs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network 100. For example, macro Node Bs may have a high transmit power level (e.g., 20 Watts) whereas pico Node Bs, femto Node Bs and relays may have a lower transmit power level (e.g., 1 Watt) .

The wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, the Node Bs may have similar frame timing, and transmissions from different Node Bs may be approximately aligned in time. For asynchronous operation, the Node Bs may have different frame timing, and transmissions from different Node Bs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.

A network controller 130 may couple to a set of Node Bs and provide coordination and control for these Node Bs. The network controller 130 may communicate with the Node Bs 110 via a backhaul. The Node Bs 110 may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a terminal, a mobile station, a subscriber unit, a station, etc. A UE may be a cellular phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a netbook, a smart book, etc. A UE may be able to communicate with macro Node Bs, pico Node Bs, femto Node Bs, relays, etc. In FIG. 1, a solid line with double arrows indicates desired transmissions between a UE and a serving Node B, which is a Node B designated to serve the UE on the downlink and/or uplink. A dashed line with double arrows indicates interfering transmissions between a UE and a Node B.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a ‘resource block’ ) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal FFT size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks) , and there may be 1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR. NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. A single component carrier bandwidth of 100 MHZ may be supported. Each radio frame may be 10 ms long and consist of 50 slots. Consequently, each slot may have a length of 0.2 ms. In alternative embodiments, each slot may have a length of 0.5 ms. In NR, “slots” may also refer to “mini-slots, ” which may be one to two symbol periods long. Each slot may indicate a link direction (i.e., DL or UL) for data transmission and the link direction for each slot may be dynamically switched. Each slot may include DL/UL data as well as DL/UL control data. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. Alternatively, NR may support a different air interface, other than an OFDM-based interface. NR networks may include entities such as central units, distributed units, data nodes, access nodes, and access control nodes.

FIG. 2 shows an exemplary downlink (DL) frame structure used in a telecommunication systems (e.g., LTE) . The transmission timeline for the downlink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms) ) and may be partitioned into 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., 7 symbol periods for a normal cyclic prefix (as shown in FIG. 2) . The available time frequency resources may be partitioned into resource blocks. Each resource block may cover N subcarriers (e.g., 12 subcarriers) in one slot.

The Node B may send a downlink control channel (e.g., a Physical Downlink Control Channel (PDCCH) ) in the first M symbol periods of each slot (M＝3 in FIG. 2) . The downlink control channel may carry information on uplink and downlink resource allocation for UEs and power control information for uplink channels. The Node B may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each slot. The PDSCH may carry data for UEs scheduled for data transmission on the downlink. There may also be an uplink burst at the end of the slot.

The Node B may send the PDCCH to groups of UEs or in a unicast manner to specific UEs in certain portions of the system bandwidth. The Node B may send the PDSCH in a unicast manner to specific UEs in specific portions of the system bandwidth.

A UE may be within the coverage of multiple Node Bs. One of these Node Bs may be selected to serve the UE. The serving Node B may be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR) , etc.

FIG. 3 is a diagram 300 illustrating an example of an uplink (UL) frame structure in a telecommunications system (e.g., LTE) . The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

A UE may be assigned

resource blocks

310a, 310b to transmit control information to a Node B. The UE may also be assigned

resource blocks

320a, 320b to transmit data to the Node B. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks. The UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may hop across frequency.

FIG. 4 illustrates example components of the base station/Node B 110 and UE 120 illustrated in FIG. 1, which may be used to implement aspects of the present disclosure. One or more components of the AP 110 and UE 120 may be used to practice aspects of the present disclosure. For example, antennas 452, Tx/Rx 222,

processors

466, 458, 464, and/or controller/processor 480 of the UE 120 and/or antennas 434,

processors

460, 420, 438, and/or controller/processor 440 of the BS 110 may be used to perform the operations described herein and illustrated with reference to FIGs. 7-8.

FIG. 4 shows a block diagram of a design of a base station/Node B 110 and a UE 120, which may be one of the base stations/Node Bs and one of the UEs in FIG. 1. For a restricted association scenario, the base station 110 may be the macro Node B 110c in FIG. 1, and the UE 120 may be the UE 120y. The base station 110 may also be a base station of some other type. The base station 110 may be equipped with antennas 434a through 434t, and the UE 120 may be equipped with antennas 452a through 452r.

At the base station 110, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for the PDSCH, etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal. A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.

At the UE 120, the antennas 452a through 452r may receive the downlink signals from the base station 110 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 454 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive and process data (e.g., for the PUSCH) from a data source 462 and control information (e.g., for the PUCCH) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal. The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators 454a through 454r (e.g., for SC-FDM, etc. ) , and transmitted to the base station 110. At the base station 110, the uplink signals from the UE 120 may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120. The receive processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/

processors

440 and 480 may direct the operation at the base station 110 and the UE 120, respectively. The processor 440 and/or other processors and modules at the base station 110 may perform or direct, e.g., the execution of various processes for the techniques described herein. The processor 480 and/or other processors and modules at the UE 120 may also perform or direct, e.g., the execution of the functional blocks illustrated in FIGs. 12-14, and/or other processes for the techniques described herein. The

memories

442 and 482 may store data and program codes for the base station 110 and the UE 120, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

FIG. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the Node B is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer 506. Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and Node B over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control (MAC) sublayer 510, a radio link control (RLC) sublayer 512, and a packet data convergence protocol (PDCP) 514 sublayer, which are terminated at the Node B on the network side. Although not shown, the UE may have several upper layers above the L2 layer 508 including a network layer (e.g., IP layer) that is terminated at the PDN gateway 118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .

The PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between Node Bs. The RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) . The MAC sublayer 510 provides multiplexing between logical and transport channels. The MAC sublayer 510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and Node B is substantially the same for the physical layer 506 and the L2 layer 508 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer 516 in Layer 3 (L3 layer) . The RRC sublayer 516 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the Node B and the UE.

New radio (NR) may refer to radios configured to operate according a wireless standard, such as 5G (e.g. wireless network 100) . NR may include Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. 80 MHz beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g. 60 GHz) , massive MTC (mMTC) targeting non-backward compatible MTC techniques, and mission critical targeting ultra reliable low latency communications (URLLC) .

NR cell may refer to a cell operating according in the NR network. A NR Node B (e.g., Node B 110) may correspond to one or multiple transmission and reception points (TRPs) . As used herein, a cell may refer to a combination of downlink (and potentially also uplink) resources. The linking between the carrier frequency of the downlink resources and the carrier frequency of the uplink resources is indicated in the system information (SI) transmitted on the downlink resources. For example, system information can be transmitted in a physical broadcast channel (PBCH) carrying a master information block (MIB) .

NR RAN architecture may include a central unit (CU) (e.g., central unit 140) . The CU may be an Access node controller (ANC) . The CU terminates backhaul interface to a RAN core network (RAN-CN) and terminates backhaul interface to one or more neighbor RAN nodes. The RAN may include a distributed unit that may be one or more TRPs that may be connected to one or more ANCs (not shown) . TRPs may advertise System Information (e.g., Global TRP ID) , may include PDCP/RLC/MAC functions, may comprise one or more antenna ports, may be configured to individually (dynamic selection) or jointly (joint transmission) transmit to UEs, and may serve traffic to the UE.

EXAMPLE CSI FEEDBACK FOR HIGH RESOLUTION BEAM COMBINATION CODEBOOK

Advanced wireless communications systems support high resolution beam combination codebooks for improving higher order MU-MIMO performance. The advanced codebook may be limited, for example, being only defined for

ranks

1 and 2. Compared to legacy beam selection codebook, there may be a significant increase on PMI feedback overhead (e.g., 13-bits for 1st PMI and 6 or 12-bits for 2nd PMI for

rank

1 and 2 respectively) . The large PMI overhead may prevent the use of the existing PUCCH format 2 for single CC periodic CSI reporting. Channel state information (CSI) includes precoding matrix indicators (PMI) , precoding type inidcators (PTI) , rank indicator (RI) , and. channel quality indicators (CQI) , The preferred set of weights that an eNodeB uses during multi-user MIMO and closed loop spatial multiplexing is provided as feedback by a PMI report. A UE uses PMI to signal a preferred set of weights to be applied during precoding. The PMI value refers to the codebook table.

Traditional multiple-input multiple-output (MIMO) systems mostly consider only the azimuth dimension of the three-dimensional (3D) multipath propagation. Full-dimension MIMO (FD-MIMO) exploiting the additional elevation dimension inherent in a MIMO wireless system with a two-dimensional (2D) active-antenna array (AAA) can achieve substantial capacity improvement. The most popular 2D antenna array is a 64-TX cross-polarized uniform planar antenna array comprising 8 columns, each column having 8 vertical antenna elements, arranged as illustrated by the example array 600 shown in FIG. 6.

Various FD-MIMO operations may be supported. Examples include Class A eMIMO-Type, as shown in FIG. 7, using non-precoded CSI-RS with one CSI-RS resource of 8/12/16 CSI-RS ports. This category involves schemes where different CSI-RS ports have the same wide beam width and direction and hence generally cell wide coverage. In this case, the UE reports RI and CQI as well as PMI which consists of a 1st PMI corresponding to {i11, i12} and one or multiple second PMI i2.

Class B eMIMO-Type, as shown in FIG. 8, uses beamformed CSI-RS with either K＝1 or K>1 CSI-RS resources where each CSI-RS has 1 to 8 antenna ports. This category involves schemes where (at least at a given time/frequency) CSI-RS ports have narrow beam widths and hence not cell wide coverage, and at least some CSI-RS port-resource combinations have different beam directions. Class B with K>1 corresponding to cell specific beamformed CSI-RS and class B K＝1 may be used for UE specific beamformed CSI-RS with dedicated resource per UE. In this case, the UE reports CQI, PMI (1D codebook) and RI as well as CRI (if K>1) , where CRI is a CS-RS resource indicator.

For efficiently supporting higher order MU-MIMO, the specification of advanced CSI with beam combination codebook may be used. As illustrated in FIG. 9, a set of orthogonal DFT beams (e.g., 2) was selected as the basis which was linear combined with wideband amplitude and subband QPSK phase. The CSI feedback may be generated, as shown in FIG. 10. In some examples, a physical uplink control channel (PUCCH) is configured for transmission of channel state information (CSI) feedback which includes a rank indicator (RI) , and a precoding matrix (W1, W2) . The rank indicator (RI) and the precoding matrix (W1, W2) are jointly encoded and codebook subsampled for at least one of the PUCCH formats. With codebook subsampling, the codeword of a codeword pair which has the smallest chordal distance is deleted.

In the prior art, the UE may transmit a physical uplink control channel (PUCCH) of format 2, 2a, or 2b containing the CQI/PMI or RI Advanced CSI reporting may support both PUSCH and PUCCH based CSI feedback. However, due to increased PMI overhead, the existing PUCCH format 2 (PF2) for a single CC’s P-CSI cannot be used for advanced CSI reporting in which precoding matrices W1 and W2, corresponding to the reported 1st and 2nd PMI are fed back. For example, if W2 and CQI are jointly reported in one subframe, the total payload size will be 10bits for rank 1 and 19 bits for rank 2, while PF2 can only support up to 11 bits. And the W1 payload is dependent on number of antenna ports, ranging from 5 bits (4Tx or 4 antennaes) to 13 bits (32Tx or 32 antennaes) , as illustrated in FIG. 11, which is too large for PF2.

Aspects of the present disclosure, provide techniques that may help solve periodic CSI reporting on PUCCH when advanced CSI is configured. In one example, the present patent application discloses how to feedback W1 and W2 to reduce payload measured in bits.

FIG. 12 illustrates example operations 1200 for wireless communications by a wireless node, such as a UE, according to aspects of the present disclosure. Operations 1200 may begin at 1202, by receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports. At 1204, the UE generates CSI feedback, based on the CSI-RS and subsampling of a first codebook. At 1206, the UE reports the generated CSI feedback. Different complex weights applied to the signals to be transmitted on the different antennaes may be referred to as a precoding vector to the transmitted signal. A precoder codebook contains a limited set of precoder vectors from which the terminal may select a suitable vector.

According to certain aspects, the subsampling may be performed by fixing the power scaling factor of the second beam to 0. In such a case, as illustrated in FIG. 13, with the power scaling factor of the second beam set to 0, the beam combination codebook will effectively fall back to a legacy beam selection codebook (as can be seen with comparison to FIG. 10) . In this case, the total payload of CQI and PMI may be no more than 11 bits, which fits in the PUCCH format 2 (PF2) capacity.

Therefore, W1 feedback may select a 2D DFT beam from oversampled grid for two polarizations with a payload [log₂ (N₁N₂O₁O₂) ] where N1 and N2 are number of antenna ports per dimension and O1 and O2 are configured oversampling factors. W2 feedback may be used to determine subband phase weighting of the selected beam on two polarizations, for example, x-polarization co-phasing with a payload of 2 bits and 4 bits for rank 1 and rank 2 (based on separate coding for each layer) .

As illustrated in FIG. 14, which shows the PMI overhead after subsampling for 32-ports, it can be seen that total CSI payload is less than 11 bits and it is possible to use PF2 for CIS reporting.

Another approach to CSI-RS feedback is to select a PUCCH format for CSI feedback based on the payload size of the CSI.

FIG. 15 is a flowchart illustrating example operations 1500 for wireless communications by a wireless node, such as a UE, according to aspects of the present disclosure. Operations 1500 may begin, at 1502, by receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports. At 1504, the UE generates CSI feedback, based on the CSI-RS.

At 1506, the UE selects a physical uplink control channel (PUCCH) format for CSI feedback with precoding matrix indicator (PMI) based, at least in part, on a payload size of the CSI feedback. At 1508 the UE reports the CSI feedback using a PUCCH of the selected format.

As an example of dynamically selected PUCCH format, PUCCH format 3 (PF3) may be used for advanced CSI feedback on PUCCH, with dynamic PUCCH format adaptation allowed according to reported CSI type and payload size. For example, as illustrated in FIG. 16, PUCCH format 2 (PF2) may be used for RI only feedback. For CSI with W1 or W2/CQI, the PUCCH format used may be determined based on whether total payload size is larger than 11 bits. For example, PF2 may be used for up to 11 bits of payload, otherwise PF3 may be used. This may mean that for 32-ports, if the reported rank is 1-2, PF3 is used for W1 or W2/CQI reporting and for rank 3-8, PF2 is used for W1 or W2/CQI reporting. This approach may achieve benefits of more efficient/larger multiplexing capability of PF2.

Currently, PF3 is used for HARQ-ACK feedback for multi-CCs and a 2-bit ARI (ACK/NACK resource indicator) can be used to select one of the four resource values configured by higher layer for PF3. The ARI value is indicated by TPC field in the DCI format of the corresponding PDCCH/EPDCCH for PDSCH transmission.

As illustrated in FIG. 17, for periodic CSI reporting with PF3, there is no PDCCH/EPDCCH for dynamic PF3 resource selection and one alternative is to use the latest PF3 PUCCH resource for HARQ-ACK feedback, e.g., indicated by the latest received ARI. If there is no ARI received before CSI feedback, then the lowest index resource value, e.g., corresponding to ARI＝’ 00’ is selected. Compared to using a fixed PF3 PUCCH resource index for CSI feedback, this dynamic approach could increase resource multiplexing.

Another solution is to relax the restriction on the maximum number of RBs for uplink control information (UCI) only feedback on PUSCH.

FIG. 18 is a flowchart illustrating example operations 1800 for wireless communications by a UE, for CSI reporting, according to aspects of the present disclosure. The operations 1800 begin, at 1802, by determining a restriction on a maximum number of resource blocks (RBs) available for uplink control information in a physical uplink shared channel (PUSCH) based, at least in part, based on a type of channel station information (CSI) reporting. At 1804, the UE reports CSI feedback in accordance with the determination.

Currently, the network can trigger the A-CSI only transmission on PUSCH if there is no transport block for the UL-SCH. The following criteria may be used to determine whether there is only A-CSI feedback for the current PUSCH reporting mode: If DCI format 0 is used or, if DCI format 4 is used and only 1 TB is enabled and the number of transmission layers is 1, and if the "CSI request"bit field is 1 bit and the bit is set to trigger an aperiodic report and N_PRB <＝4 (e.g. for non-CA) . Or the "CSI request" bit field is 2 bits and when there are K>1 CSI processes triggered for reporting and N_PRB <＝20 (e.g., for CA) . For advanced CSI reporting on PUSCH, the restriction on the maximum number of RBs for A-CSI reporting without UL-SCH may be relaxed in order to ensure sufficiently low coding rate.

As one example, if subband CQI/PMI is configured then for 20MHz the total CQI/PMI overhead for rank 2 would be #subbands ＝ 13, wideband W1 ＝ 13 bits, subband W2＝12 bits, subband CQI ＝ 4 bits, wideband CQI＝8bits thus total 13* (12+4) +8+13＝229. Assuming 4 symbols used for RI, there is 8 symbols that can be used for CQI/PMI transmission and for N_RB＝4 and QPSK the coding rate is 229/ (8*12*4*2) ≈ 0.3. Therefore, the lowest coding rate for advanced CSI only feedback on PUSCH without UL-SCH may be limited to 0.3 if max #RB is limited to 4. Therefore, there could be no restriction on the max #of RBs (unlike 4 or 20 RBs as Rel-12) when there is advanced CSI triggered for reporting on PUSCH without UL-SCH (Rel-12 rule is still applied when non-advanced CSI is triggered for reporting on PUSCH w/o UL-SCH) .

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged 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.

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. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. For example, operations 700 illustrated in FIG. 7 correspond to means 700A illustrated in FIG. 7A, and operations 800 illustrated in FIG. 8 correspond to means 800A illustrated in FIG. 8A.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with 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, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, 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 case of a user terminal 120 (see FIG. 1) , a user interface (e.g., 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, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer-readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, 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 medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

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. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise 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, instructions for determining a maximum available transmit power of the UE, instructions for semi-statically configuring a first minimum guaranteed power available for uplink transmission to a first base station and a second minimum guaranteed power available for uplink transmission to a second base station, and instructions for dynamically determining a first maximum transmit power available for uplink transmission to the first base station and a second maximum transmit power available for uplink transmission to the second base station based, at least in part, on the maximum available transmit power of the UE, the first minimum guaranteed power, and the second minimum guaranteed power.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. 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.

WHAT IS CLAIMED IS:

Claims

A method for wireless communications by a user equipment (UE) , comprising:

receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports；

generating CSI feedback, based on the CSI-RS and subsampling of a first codebook； and

reporting the generated CSI feedback.
The method of claim 1, wherein PUCCH format 3 is used if the payload size is larger than 11 bits and PUCCH format 2 is used if the payload size is 11 bits or less for CSI with W1 or W2 and CQI feedback.
The method of claim 1, wherein:

the first codebook is based on a combination of at least two beams； and

the subsampling of the first codebook is achieved by fixing a power scaling factor of at least one of the beams to zero.
The method of claim 3, wherein the subsampling results effectively results in falling back to a second codebook having a lower resolution than the first codebook.
The method of claim 1, wherein the generated CSI feedback is reported via a physical uplink control channel (PUCCH) .
The method of claim 4, wherein:

the CSI-RS is transmitted via at least 32-ports； and

the CSI feedback is reported via a PUCCH format 2.
A method for wireless communications by a user equipment (UE) , comprising:

receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports；

generating CSI feedback, based on the CSI-RS；

selecting a physical uplink control channel (PUCCH) format for CSI feedback with precoding matrix indicator (PMI) based, at least in part, on a payload size of the CSI feedback； and

reporting the CSI feedback using a PUCCH of the selected format.
The method of claim 7, wherein the selecting comprises:

selecting a first PUCCH format if the payload size is equal to or less than a first threshold value； and

selecting a second PUCCH format if the payload size is greater than the first threshold value.
The method of claim 8, wherein:

a first PUCCH format is PUCCH format 2 and a second PUCCH format is PUCCH format 3.
The method of claim 7, wherein:

a PUCCH format 2 is selected for CSI feedback with rank indicator (RI) only.
The method of claim 7, further comprising:

determining a resource to use for reporting the CSI feedback if a PUCCH format 3 is selected for CSI feedback with PMI.
The method of claim 11, wherein the determining comprises at least one of:

receiving an indication via an ACK/NACK resource indicator (ARI) ；

selecting a lowest index resource from a number of higher layer configured resources if no ARI is received.
A method for wireless communications by a user equipment (UE) , comprising:

determining a restriction on a maximum number of resource blocks (RBs) available for uplink control information in a physical uplink shared channel (PUSCH) based, at least in part, based on a type of channel station information (CSI) reporting； and

reporting CSI feedback in accordance with the determination.
The method of claim 13, wherein the determination is designed to ensure a sufficiently low coding rate.
The method of claim 13, wherein the determination is for no restriction on the maximum number of RBs when there is advanced CSI triggered for reporting on PUSCH without an uplink shared channel (UL-SCH) .
An apparatus for wireless communications, comprising:

means for receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports；

means for generating CSI feedback, based on the CSI-RS and subsampling of a first codebook； and

means for reporting the generated CSI feedback.
The apparatus of claim 16, wherein PUCCH format 3 is used if the payload size is larger than 11 bits and PUCCH format 2 is used if the payload size is 11 bits or less for CSI with W1 or W2 and CQI feedback.
The apparatus of claim 16, wherein:

the first codebook is based on a combination of at least two beams； and

the subsampling of the first codebook is achieved by fixing a power scaling factor of at least one of the beams to zero.
The apparatus of claim 18, wherein the subsampling results effectively results in falling back to a second codebook having a lower resolution than the first codebook.
The apparatus of claim 16, wherein the generated CSI feedback is reported via a physical uplink control channel (PUCCH) .
The apparatus of claim 19, wherein:

the CSI-RS is transmitted via at least 32-ports； and

the CSI feedback is reported via a PUCCH format 2.
An apparatus for wireless communications by a user equipment (UE) , comprising:

means for receiving channel state information reference signals (CSI-RS) , transmitted via multiple CSI-RS ports；

means for generating CSI feedback, based on the CSI-RS；

means for selecting a physical uplink control channel (PUCCH) format for CSI feedback with precoding matrix indicator (PMI) based, at least in part, on a payload size of the CSI feedback； and

means for reporting the CSI feedback using a PUCCH of the selected format.
The apparatus of claim 22, wherein the means for selecting comprises:

means for selecting a first PUCCH format if the payload size is equal to or less than a first threshold value； and

means for selecting a second PUCCH format if the payload size is greater than the first threshold value.
The apparatus of claim 23, wherein:

a first PUCCH format is PUCCH format 2 and a second PUCCH format is PUCCH format 3.
The apparatus of claim 22, wherein:

a PUCCH format 2 is selected for CSI feedback with rank indicator (RI) only.
The apparatus of claim 22, further comprising:

means for determining a resource to use for reporting the CSI feedback if a PUCCH format 3 is selected for CSI feedback with PMI.
The apparatus of claim 26, wherein the means for determining comprises at least one of:

means for receiving an indication via an ACK/NACK resource indicator (ARI) ；

means for selecting a lowest index resource from a number of higher layer configured resources if no ARI is received.
An apparatus for wireless communications by a user equipment (UE) , comprising:

means for determining a restriction on a maximum number of resource blocks (RBs) available for uplink control information in a physical uplink shared channel (PUSCH) based, at least in part, based on a type of channel station information (CSI) reporting； and

means for reporting CSI feedback in accordance with the determination.
The apparatus of claim 28, wherein the determination is designed to ensure a sufficiently low coding rate.
The apparatus of claim 28, wherein the determination is for no restriction on the maximum number of RBs when there is advanced CSI triggered for reporting on PUSCH without an uplink shared channel (UL-SCH) .