WO2016119208A1

WO2016119208A1 - Codebook and signaling for 3d mimo

Info

Publication number: WO2016119208A1
Application number: PCT/CN2015/071933
Authority: WO
Inventors: Yu Zhang; Chao Wei; Neng Wang; Jilei Hou
Original assignee: Qualcomm Incorporated
Priority date: 2015-01-30
Filing date: 2015-01-30
Publication date: 2016-08-04

Abstract

Certain aspects of the present disclosure support a method for constructing and signaling codebooks for three-dimensional (3D) multiple-input multiple-output (MIMO) communications.

Description

CODEBOOK AND SIGNALING FOR 3D MIMO

BACKGROUND

Field

Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to a method of constructing and signaling codebooks for three-dimensional (3D) multiple-input multiple-output (MIMO) communications.

Background

Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources (e.g., bandwidth and transmit power) . Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, 3^rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) networks, and Long Term Evolution Advanced (LTE-A) networks.

A wireless communication network may include a number of base stations that can support communication with a number of user equipments (UEs) . A UE may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station. A base station may transmit data and control information on the downlink to a UE and/or may receive data and control information on the uplink from the UE. This communication link may be established via a single-input single-output, multiple-input single-output or a multiple-input multiple-output (MIMO) system.

A MIMO system employs multiple (N_T) transmit antennas and multiple (N_R) receive antennas for data transmission. A MIMO channel formed by the N_T transmit and N_R receive antennas may be decomposed into N_S independent channels, which are also referred to as spatial channels, where N_S≤min {N_T, N_R} . Each of the N_S independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.

A MIMO system supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the base station to extract transmit beamforming gain on the forward link when multiple antennas are available at the base station.

SUMMARY

Certain aspects of the present disclosure provide a method for wireless communications by a base station (BS) . The method generally includes providing, to a user equipment (UE) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS, constructing a set of vertical steering vectors, based on the parameters, receiving, from the UE, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on horizontal steering vectors for the plurality of layers, generating a precoding matrix, based on the at least one CSI report, the constructed vertical steering vectors and the horizontal steering vectors for the plurality of layers, and transmitting data to the UE, via a multi-dimensional array of transmit antennas, using the precoding matrix.

Certain aspects of the present disclosure provide a method for wireless communications by a user equipment (UE) . The method generally includes receiving, from a base station (BS) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS, constructing a set of vertical steering vectors, based on the parameters, generating a plurality of precoding matrices, based on the constructed vertical steering vectors and horizontal steering vectors for the plurality of layers, providing, to the BS, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on the horizontal steering vectors for the plurality of layers, and decoding data, transmitted from the BS via a multi-dimensional array of transmit antennas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram conceptually illustrating an example of a wireless communications network, in accordance with certain aspects of the present disclosure.

FIG. 2 illustrates a block diagram conceptually illustrating an example of a frame structure in a wireless communications network, in accordance with certain aspects of the present disclosure.

FIG. 2A illustrates an example format for the uplink in Long Term Evolution (LTE) , in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates a block diagram conceptually illustrating an example of a Node B in communication with a user equipment device (UE) in a wireless communications network, in accordance with certain aspects of the present disclosure.

FIG. 4 illustrates an example structure of two-dimensional (2D) antenna array, in accordance with certain aspects of the present disclosure.

FIG. 5 illustrates example operations that may be performed at an evolved Node B (eNB) , in accordance with certain aspects of the present disclosure.

FIG. 5A illustrates example means capable of performing the operations shown in FIG. 5.

FIG. 6 illustrates example operations that may be performed at a user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 6A illustrates example means capable of performing the operations shown in FIG. 6.

DETAILED DESCRIPTION

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

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, the scope of the disclosure being defined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wireless communication networks such as 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 Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20,

etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new 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, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.

Single carrier frequency division multiple access (SC-FDMA) is a transmission technique that utilizes single carrier modulation at a transmitter side and frequency domain equalization at a receiver side. The SC-FDMA has similar performance and essentially the same overall complexity as those of OFDMA system. However, SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. The SC-FDMA has drawn great attention, especially in the uplink communications where lower PAPR greatly benefits the mobile terminal in terms of transmit power efficiency. It is currently a working assumption for uplink multiple access scheme in the 3GPP LTE, LTE-A, and the Evolved UTRA.

FIG. 1 shows an example wireless communication network 100, which may be an LTE network, in which aspects of the present disclosure may be practiced. Wireless network 100 may include a number of evolved Node Bs (eNBs) 110 and other network entities. An eNB may be a station that communicates with the user equipment devices (UEs) , and may also be referred to as a base station, a Node B, an access point, etc. Each eNB 110 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of an eNB and/or an eNB subsystem serving this coverage area, depending on the context in which the term is used.

An eNB 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. ) . An eNB for a macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. An eNB for a femto cell may be referred to as a femto eNB or a home eNB. An eNB may support one or multiple (e.g., three) cells.

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., an eNB or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or an eNB) . A relay station may also be a UE that relays transmissions for other UEs. A relay station may also be referred to as a relay eNB, a relay, etc.

Wireless network 100 may be a heterogeneous network that includes eNBs of different types, e.g., macro eNBs, pico eNBs, femto eNBs, relays, etc. These different types of eNBs may have different transmit power levels, different coverage areas, and different impact on interference in wireless network 100. For example, macro eNBs may have a high transmit power level (e.g., 20 watts) whereas pico eNBs, femto eNBs, and relays may have a lower transmit power level (e.g., 1 watt) .

Wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, the eNBs may have similar frame timing, and transmissions from different eNBs may be approximately aligned in time. For asynchronous operation, the eNBs may have different frame timing, and transmissions from different eNBs 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 eNBs and provide coordination and control for these eNBs. Network controller 130 may communicate with eNBs 110 via a backhaul. eNBs 110 may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

UEs 120 may be dispersed throughout 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, etc. A UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, etc. In FIG. 1, a solid line with double arrows indicates transmissions between a UE and a serving eNB, which is an eNB designated to serve the UE on the downlink and/or uplink.

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, K 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, 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.

FIG. 2 shows a frame structure used in 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 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., L＝7 symbol periods for a normal cyclic prefix (as shown in FIG. 2) or L＝6 symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L–1. 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.

In LTE, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in

symbol periods

6 and 5, respectively, in each of

subframes

0 and 5 of each radio frame with the normal cyclic prefix, as shown in FIG. 2. The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe, as shown in FIG. 2. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2, or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks. The eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe (not shown in FIG. 2) . The PHICH may carry information to support hybrid automatic repeat request (HARQ) . The PDCCH may carry information on resource allocation for UEs and control information for downlink channels. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink. The various signals and channels in LTE are described in 3GPP TS 36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA) ； Physical Channels and Modulation, ” which is publicly available.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of the system bandwidth used by the eNB. The eNB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent. The eNB may send the PDCCH to groups of UEs in certain portions of the system bandwidth. The eNB may send the PDSCH to specific UEs in specific portions of the system bandwidth. The eNB may send the PSS, SSS, PBCH, PCFICH and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs) . Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period 0. The PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period 0 or may be spread in

symbol periods

0, 1, and 2. The PDCCH may occupy 9, 18, 32, or 64 REGs, which may be selected from the available REGs, in the first M symbol periods. Only certain combinations of REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. The UE may search different combinations of REGs for the PDCCH. The number of combinations to search is typically less than the number of allowed combinations for the PDCCH. An eNB may send the PDCCH to the UE in any of the combinations that the UE will search.

FIG. 2A shows an exemplary format 200A for the uplink in LTE. The available resource blocks for the uplink 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 design in FIG. 2A 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 in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks in the data section to transmit data to the Node B. The UE may transmit control information in a Physical Uplink Control Channel (PUCCH) 210a, 210b on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a Physical Uplink Shared Channel (PUSCH) 220a, 220b on the assigned resource blocks in the data section. An uplink transmission may span both slots of a subframe and may hop across frequency as shown in FIG. 2A.

FIG. 3 shows a block diagram of a design of a base station (or an eNB 110) and a UE 120, which may be one of the base stations/eNBs and one of the UEs in FIG. 1. The eNB 110 may be equipped with T antennas 334a through 334t, and UE 120 may be equipped with R antennas 352a through 352r, where in general T≥1 and R≥1.

At the eNB 110, a transmit processor 320 may receive data from a data source 312 and control information from a controller/processor 340. The control information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for the PDSCH, etc. The transmit processor 320 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 320 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 330 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 332a through 332t. Each modulator 332 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 332 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 332a through 332t may be transmitted via T antennas 334a through 334t, respectively.

At UE 120, antennas 352a through 352r may receive the downlink signals from the eNB 110 and may provide received signals to demodulators (DEMODs) 354a through 354r, respectively. Each demodulator 354 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 354 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 356 may obtain received symbols from all R demodulators 354a through 354r, perform MIMO detection on the received symbols, if applicable, and provide detected symbols. A receive processor 358 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 120 to a data sink 360, and provide decoded control information to a controller/processor 380.

On the uplink, at UE 120, a transmit processor 364 may receive and process data (e.g., for the PUSCH) from a data source 362 and control information (e.g., for the PUCCH) from the controller/processor 380. The transmit processor 364 may also generate reference symbols for a reference signal. The symbols from the transmit processor 364 may be precoded by a TX MIMO processor 366 if applicable, further processed by modulators 354a through 354r (e.g., for SC-FDM, etc. ) , and transmitted to the eNB 110. At the eNB 110, the uplink signals from UE 120 may be received by antennas 334, processed by demodulators 332, detected by a MIMO detector 336 if applicable, and further processed by a receive processor 338 to obtain decoded data and control information sent by UE 120. The receive processor 338 may provide the decoded data to a data sink 339 and the decoded control information to the controller/processor 340.

Controllers/

processors

340 and 380 may direct the operation at the eNB 110 and UE 120, respectively. Controller/processor 340, TX MIMO processor 330, receive processor 338, and/or other processors and modules at the eNB 110 may perform or direct operations 500 in FIG. 5 and/or other processes for the techniques described herein. At UE 120, controller/processor 380, TX MIMO processor 366, receive processor 358, and/or other processors and modules may perform or direct operations 500 in FIG. 5 and/or other processes for the techniques described herein.

Memories

342 and 382 may store data and program codes for the eNB 110 and UE 120, respectively. A scheduler 344 may schedule UEs for data transmission on the downlink and/or uplink.

CODEBOOK AND SIGNALING FOR 3D MIMO

Traditional multiple-input multiple-output (MIMO) systems mostly consider only the azimuth dimension of the three-dimensional (3D) multipath propagation. It can be shown that significant gain of interference avoidance can potentially be achieved by dynamic beam steering in a vertical dimension. Using a two-dimensional (2D) active-antenna array (AAA) , substantial capacity improvement can be expected by exploiting the additional elevation dimension inherent in a MIMO wireless system. UE-specific 3D beamforming can be performed if channel state information (CSI) is available at a base station.

In order to exploit the vertical dimension by elevation beamforming, the CSI is needed at the base station. The CSI, in terms of precoding matrix indicator (PMI) and rank indicator (RI) , can be fed back to the base station by a mobile station based on the downlink channel estimation and predefined PMI codebook (s) . PMI codebooks for {2, 4, 8} horizontal antenna ports may be defined in current and previous 3GPP releases. These codebooks may be optimized for horizontal antenna arrays. Due to differences of propagation characteristics between vertical-and horizontal dimensions, there is a need to optimize the PMI codebook for 2D antenna arrays. In accordance with aspects of the present disclosure, “horizontal” and “vertical” are relative terms and may apply to different types of orientations.

In this disclosure, localized cross-polarization 2D arrays can be considered. The existing codebook for 2, 4, or 8 horizontal antenna ports in

LTE Releases

8, 9, 10, 11, and 12 may be reused for indicating the horizontal steering and cross-polarization co-phasing. A new vertical codebook is proposed in this disclosure for indicating the vertical steering. In some aspects of the present disclosure, in order to support various vertical antenna port-mapping implementations, the vertical codebook may be configurable by a network via Radio Resource Control (RRC) signaling. In some aspects, the configured codebook can support vertical antenna ports with a large spacing as well as a small spacing. The proposed codebook may also allow different vertical steering between different layers/cross-polarization antenna groups. This may allow better adaptation in scenarios with large and/or small elevation angular spread statistics.

FIG. 4 illustrates an example structure 400 of a two-dimensional (2D) antenna array, in accordance with certain aspects of the present disclosure. In accordance with aspects of the present disclosure, the antenna array 400 in FIG. 4 may correspond to the antennas 334 of the eNB 110 from FIG. 3. In this disclosure, as illustrated in FIG. 4, localized cross-polarization 2D arrays can be considered. As illustrated in FIG. 4, +45°and–45°antenna ports may be co-located, with 2MN ports in an M×N cross-polarization array. As illustrated in FIG. 4, +45° ports may be ports {0, 1, …, MN–1} , and–45° ports may be ports {MN, MN+1, …, 2MN–1} . In accordance with aspects of the present disclosure, typically M ＝ {2, 4, 8} and N ＝ {2, 4} .

In accordance with aspects of the present disclosure, for the M×N cross-polarization array, a rank-R precoding matrix may be defined as W ＝ (w₁…w_R) ,

r＝1, 2, …, R. In some aspects, the rank-R precoding matrix may be constructed by indicating following terms: a_+, r,

r＝1, 2, …, R, the rth layer horizontal steering for ±45° polarization ports, and b_+, r,

r＝1, 2, …, R, the rth layer vertical steering for ±45° polarization ports.

In accordance with aspects of the present disclosure, a precoding vector of the precoding matrix for the rth layer may be constructed as the Kronecker product between the horizontal and vertical steering vectors, i.e.,

In some aspects of the present disclosure, the existing codebook for 2, 4, or 8 antenna ports in

LTE Releases

8, 9, 10, 11, and 12 may be reused for indicating horizontal steering vectors a_+, r and a_-, r when N ＝ 1, 2, or 4. New vertical codebooks are needed for indicating vertical steering vectors b_+, , b_-, r.

In accordance with certain aspects of the present disclosure, the sufficient condition for creating orthogonal layers may be given as:

When reusing the existing codebook for 2, 4, or 8 antenna ports in

LTE Releases

8, 9, 10, 11, and 12 for indicating a_+， r and a_-， r, the following holds:

a_-, ＝γ_ra₊, (3)

Thus, the sufficient condition can be reduced to:

In an aspect of the present disclosure, the layers mat be H-orthogonal, i.e., a_+r ^Ha_+s ＝ 0. In another aspect, the layers may be V-orthogonal, i.e., b_+, +, s＝ 0, b_-, r ^Hb_-, s ＝ 0. In yet another aspect, the layers may be X-orthogonal, i.e., γ_r ^*γ_s＝-1, b_+, ＝b_-, , b_+, _s＝b_-, s. In yet another aspect, the layers may be VX-orthogonal, i.e., b_+, r ^Hb_+, s+ γ_r ^*γ_sb_-, r ^Hb_-, s＝ 0.

In accordance with aspects of the present disclosure, the vertical steering for each polarization may be the product of two matrices

wherein the 1^st matrix on the right-hand side of equation (5) may be selected from the 1^st codebook,

and the 2^nd matrix on the right-hand side of equation (5) may be selected from the 2^nd codebook,

.

In some aspects, for each feasible M, a pair of codebooks {

} may be defined for the rank-R PMI reporting. In an aspect of the present disclosure, the codebook pairs used for CSI reporting may be configured implicitly, i.e., via CSI-RS port association. In another aspect, the codebook pairs used for CSI reporting may be configured explicitly, i.e., via RRC signaling.

In some aspects of the present disclosure, the 1^st codebook may define multiple grids of beams (GoB) , i.e.,

where

ω_k＝ exp (j2πk/LM) , L is an oversampling factor, LM can be a predefined constant, k is an index of the first beam in the grid, s is the stride within the grid, N_b is a predefined constant, and Q is a number of beams per grid (predefined) . In an aspect, a size of the 2^nd codebook may depend on N_b.

In some aspects, the feasible set

may be a subset of {0, 1, …, LM–1} . In an aspect,

may depend on the specific deployment scenario. The first codebook size N₁ may be equal to

In an aspect, the value of s may depend on d_V (vertical antenna spacing) . In accordance with aspects of the present disclosure,

and s can be configured via RRC signaling to adapt deployment scenarios and eNB antenna virtualization.

In some aspects of the present disclosure, design parameters {

L, Q, s} may be pre-determined. In an aspect,

can be determined by the desired vertical coverage, wherein {Q, s} can be determined by:

where d_V is a vertical antenna spacing, Δθ is a zenith spread, and λ is a wavelength. In an aspect of the present disclosure, {L, s} can be determined by the expected beamforming gain.

In some aspects of the present disclosure, the value of s (the stride within the grid) may be indicated by an integer. In an aspect,

may be indicated by a (LM) -bit bitmap

i.e.,

For example, if LM ＝ 16, N_b ＝ 2, the feasible set

can be indicated by

If s＝ 1 is signaled, the resulting GoBs may be { {1, 2, 3, 4} , {3, 4, 5, 6} , {13, 14, 15, 1} , {15, 1, 3, 4} } .

In another aspect,

may be indicated by an offset k₀ and a step size

i.e.,

mod LM: n ＝ 0, 1, …, N₁-1} . For example, the feasible set in the previous example can be indicated by k₀＝ 1 and

In some aspects of the present disclosure, the 2^nd codebook may define the selection of R beams out of the GoBs defined by the first codebook. The 2^nd codebook may be defined as:

Y_+, l ＝ (y_+1l y_+2l … y_+Rl) ,

Y_-, l ＝ (y_-1l y_-2l … y_-Rl) , (8)

where y_+rl, y_-rl∈ {e₁, e₂, …, e_Nb} , r＝1, 2, …, R, e_q, q＝1, 2, …, N_b, is the qth column of the N_b-dimensional identity matrix.

In an aspect of the present disclosure, when N_b> 2, enumeration of all possible beam selections may lead to a large 2^nd codebook. In such case, a bitmap may be configured to indicate which codewords shall be considered in CSI reporting.

In some aspects of the present disclosure, when N_b ＝ 2, a possible 2^nd codebook may be given as (for ranks 1 through 8, respectively) :

Aspects of the present disclosure support layer/x-polarization specific vertical steering, i.e., b_+, ≠b_-, and/or b_+, r≠b_+, r′and/or b_-, r≠b_-, r′. In an aspect of the present disclosure, the 1^st codebook may be rank-common. In another aspect, the 1^st codebook may be rank-common configurable codebook, based on signaling for setting

and s. In yet another aspect, codebook subset restriction may be provided for the 2^nd codebook

In an aspect of the present disclosure, the horizontal steering a_r and the cross-polarization co-phasing γ_r may be jointly fed back (e.g., from UE to BS) . In addition, the vertical steering b₊, and b_-, may be jointly fed back. In another aspect, the vertical steering b_+, , b_-, r and the cross-polarization co-phasing γ_r may be jointly fed back, wherein the horizontal steering a_r may be in a separate feedback. In yet another aspect, the horizontal steering a_r and the vertical steering b_+, , b_-, r may be jointly fed back, wherein the cross-polarization co-phasing γ_r may be in a separate feedback.

FIG. 5 illustrates example operations 500 that may be performed at an evolved Node B (eNB) or a base station (BS) , in accordance with certain aspects of the present disclosure. These operations 500 may be executed, for example, at the processor (s) 340, 330, and/or 338 of the eNB 110 from FIG. 3. The operations 500 and other aspects of the present disclosure refer mainly to LTE-A systems, but are applicable to any other suitable MIMO system.

The operations 500 may begin, at 502, by providing, to a user equipment (UE) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS. At 504, a set of vertical steering vectors may be constructed based on the parameters. At 506, the BS may receive, from the UE, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on horizontal steering vectors for the plurality of layers. At 508, a precoding matrix may be generated, based on the at least one CSI report, the constructed vertical steering vectors and the horizontal steering vectors for the plurality of layers. At 510, the BS may transmit data to the UE, via a multi-dimensional array of transmit antennas, using the precoding matrix.

In an aspect of the present disclosure, as discussed, for each layer, a precoding vector of the precoding matrix may be constructed by the Kronecker product of at least one of the vertical steering vectors and at least one of the horizontal steering vectors. In some aspects, the vertical steering vectors may be associated with different polarization ports of the multi-dimensional array of transmit antennas. In an aspect of the present disclosure, as discussed, for a same layer, different vertical steering vectors may be constructed for different polarization ports of the multi-dimensional array of transmit antennas. In another aspect, for different layers, different vertical steering vectors may be constructed for a same polarization port of the multi-dimensional array of transmit antennas.

In accordance with aspects of the present disclosure, the vertical steering vectors may be constructed using at least a first codebook and a second codebook, based on the parameters. In an aspect, at least one of the first or second codebooks may be independent of rank. In some aspects, as discussed, the first codebook may define multiple grids of beams, and the second codebook may define selection of beams out of the grids of beams for constructing the vertical steering vectors for the plurality of layers and for different polarization ports of the multi-dimensional array of transmit antennas.

In accordance with aspects of the present disclosure, the BS may provide an indication to the UE of one or more constraints on using at least one of first or second codebooks when generating the vertical steering vectors. In an aspect of the present disclosure, the parameters may comprise at least a first parameter indicative of an index of a first beam in a grid of a multiple grids of beams defined by the first codebook. In another aspect, the parameters may comprise at least a second parameter indicative of a stride within the grid, wherein the stride depends on vertical spacing of antennas in the multi-dimensional array of transmit antennas. In yet another aspect, the parameters may comprise at least a third parameter indicative of a bitmap related to a subset of the second codebook that is being restricted for CSI reporting. In some aspects, at least one of the first, second, and third parameters are provided to the UE via radio resource control (RRC) signaling. In some aspects, the one or more constraints on using the at least one of first or second codebooks may comprise a first set of constraints for CSI reporting (e.g., from the UE to the BS) associated with single-user multiple-input multiple-output (SU-MIMO) operation, and a second set of constraints for CSI reporting associated with multi-user multiple-input multiple-output (MU-MIMO) operation.

FIG. 6 illustrates example operations 600 that may be performed at a user equipment (UE) , in accordance with certain aspects of the present disclosure. These operations 600 may be executed, for example, at the processor (s) 358, 380, and/or 364 of the UE 120 from FIG. 3. The operations 600 and other aspects of the present disclosure refer mainly to LTE-A systems, but are applicable to any other suitable MIMO system.

The operations 600 may begin, at 602, by receiving, from a base station (BS) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS. At 604, a set of vertical steering vectors may be constructed, based on the parameters. At 606, a plurality of precoding matrices may be generated, based on the constructed vertical steering vectors and horizontal steering vectors for the plurality of layers. At 608, the UE may provide, to the BS, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on the horizontal steering vectors for the plurality of layers. At 610, the UE may decode data, transmitted from the BS via a multi-dimensional array of transmit antennas.

In accordance with aspects of the present disclosure, the UE may receive, from the BS, an indication of one or more constraints on using at least one of first or second codebooks when generating the vertical steering vectors. In an aspect of the present disclosure, the parameters may comprise at least a first parameter indicative of an index of a first beam in a grid of a multiple grids of beams defined by the first codebook. In another aspect, the parameters may comprise at least a second parameter indicative of a stride within the grid, wherein the stride depends on vertical spacing of antennas in the multi-dimensional array of transmit antennas. In yet another aspect, the parameters may comprise at least a third parameter indicative of a bitmap related to a subset of the second codebook that is being restricted for CSI reporting. In some aspects, at least one of the first, second, and third parameters may be received from the BS via radio resource control (RRC) signaling. In some aspects, the one or more constraints on using the at least one of first or second codebooks may comprise a first set of constraints for CSI reporting (e.g., from the UE to the BS) associated with single-user multiple-input multiple-output (SU-MIMO) operation, and a second set of constraints for CSI reporting associated with multi-user multiple-input multiple-output (MU-MIMO) operation.

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

500 and 600 illustrated in FIG. 5 and FIG. 6 correspond to means 500A and 600A illustrated in FIG. 5A and FIG. 6A.

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.

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.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

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.

The steps of a method or algorithm described in connection with the present disclosure may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in any form of storage medium that is known in the art. Some examples of storage media that may be used include random access memory (RAM) , read only memory (ROM) , flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM and so forth. 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. A 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.

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.

The functions described may be implemented in hardware, software, firmware, or any combination thereof. 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, 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 responsible for managing the bus and general processing, including the execution of software stored on the machine-readable media. 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. 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. Machine-readable 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. The computer-program product may comprise packaging materials.

In a hardware implementation, the machine-readable media may be part of the processing system separate from the processor. However, as those skilled in the art will readily appreciate, the machine-readable media, or any portion thereof, may be external to the processing system. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer product separate from the wireless node, all 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.

The processing system may be configured as a general-purpose processing system with one or more microprocessors providing the processor functionality and external memory providing at least a portion of the machine-readable media, all linked together with other supporting circuitry through an external bus architecture. Alternatively, the processing system may be implemented with an ASIC (Application Specific Integrated Circuit) with the processor, the bus interface, the user interface in the case of an access terminal) , supporting circuitry, and at least a portion of the machine-readable media integrated into a single chip, or with one or more FPGAs (Field Programmable Gate Arrays) , PLDs (Programmable Logic Devices) , controllers, state machines, gated logic, discrete hardware components, or any other suitable circuitry, or any combination of circuits that can perform the various functionality described throughout this disclosure. 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.

The machine-readable media may comprise a number of software modules. The software modules include instructions that, when executed by the 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.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer-readable medium. 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. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. 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 certain aspects, the computer program product may include packaging material.

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 base station (BS) , comprising:

providing, to a user equipment (UE) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS；

constructing a set of vertical steering vectors, based on the parameters；

receiving, from the UE, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on horizontal steering vectors for the plurality of layers；

generating a precoding matrix, based on the at least one CSI report, the constructed vertical steering vectors and the horizontal steering vectors for the plurality of layers； and

transmitting data to the UE, via a multi-dimensional array of transmit antennas, using the precoding matrix.
The method of claim 1, wherein:

for each layer, a precoding vector of the precoding matrix is constructed by the Kronecker product of at least one of the vertical steering vectors and at least one of the horizontal steering vectors.
The method of claim 1, wherein the vertical steering vectors are associated with different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 1, wherein:

for a same layer, different vertical steering vectors are constructed for different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 1, wherein:

for different layers, different vertical steering vectors are constructed for a same polarization port of the multi-dimensional array of transmit antennas.
The method of claim 1, wherein the vertical steering vectors are constructed using at least a first codebook and a second codebook, based on the parameters.
The method of claim 6, wherein at least one of the first or second codebooks is independent of rank.
The method of claim 6, wherein the first codebook defines multiple grids of beams.
The method of claim 8, wherein:

the second codebook defines selection of beams out of the grids of beams for constructing the vertical steering vectors for the plurality of layers and for different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 1, further comprising:

providing an indication to the UE of one or more constraints on using at least one of first or second codebooks when generating the vertical steering vectors.
The method of claim 10, wherein:

the parameters comprise at least a first parameter indicative of an index of a first beam in a grid of a multiple grids of beams defined by the first codebook.
The method of claim 11, wherein:

the parameters comprise at least a second parameter indicative of a stride within the grid, wherein the stride depends on vertical spacing of antennas in the multi-dimensional array of transmit antennas.
The method of claim 10, wherein:

the parameters comprise at least a third parameter indicative of a bitmap related to a subset of the second codebook that is being restricted for CSI reporting.
The method of claim 13, wherein at least one of the first, second, and third parameters are provided to the UE via radio resource control (RRC) signaling.
The method of claim 10, wherein the one or more constraints on using the at least one of first or second codebooks comprise:

a first set of constraints for CSI reporting associated with single-user multiple-input multiple-output (SU-MIMO) operation, and

a second set of constraints for CSI reporting associated with multi-user multiple-input multiple-output (MU-MIMO) operation.
A method for wireless communications by a user equipment (UE) , comprising:

receiving, from a base station (BS) , one or more parameters indicative of vertical steering vectors for a plurality of layers associated with a plurality of transmissions by the BS；

constructing a set of vertical steering vectors, based on the parameters；

generating a plurality of precoding matrices, based on the constructed vertical steering vectors and horizontal steering vectors for the plurality of layers；

providing, to the BS, at least one channel state information (CSI) report, wherein the at least one CSI report comprises at least one vertical precoding matrix indicator (V-PMI) based on the constructed vertical steering vectors and at least one horizontal precoding matrix indicator (H-PMI) based on the horizontal steering vectors for the plurality of layers； and

decoding data, transmitted from the BS via a multi-dimensional array of transmit antennas.
The method of claim 16, wherein:

for each layer, a precoding vector of the precoding matrices is constructed by the Kronecker product of at least one of the vertical steering vectors and at least one of the horizontal steering vectors.
The method of claim 16, wherein the vertical steering vectors are associated with different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 16, wherein:

for a same layer, different vertical steering vectors are constructed for different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 16, wherein:

for different layers, different vertical steering vectors are constructed for a same polarization port of the multi-dimensional array of transmit antennas.
The method of claim 16, wherein the vertical steering vectors are constructed using at least a first codebook and a second codebook, based on the parameters.
The method of claim 21, wherein at least one of the first or second codebooks is independent of rank.
The method of claim 21, wherein the first codebook defines multiple grids of beams.
The method of claim 23, wherein:

the second codebook defines selection of beams out of the grids of beams for constructing the vertical steering vectors for the plurality of layers and for different polarization ports of the multi-dimensional array of transmit antennas.
The method of claim 16, further comprising:

receiving, from the BS, an indication of one or more constraints on using at least one of first or second codebooks when generating the vertical steering vectors.
The method of claim 25, wherein:

the parameters comprise at least a first parameter indicative of an index of a first beam in a grid of a multiple grids of beams defined by the first codebook.
The method of claim 26, wherein:

the parameters comprise at least a second parameter indicative of a stride within the grid, wherein the stride depends on vertical spacing of antennas in the multi-dimensional array of transmit antennas.
The method of claim 28, wherein:

the parameters comprise at least a third parameter indicative of a bitmap related to a subset of the second codebook that is being restricted for CSI reporting.
The method of claim 28, wherein at least one of the first, second, and third parameters are received from the BS via radio resource control (RRC) signaling.
The method of claim 25, wherein the one or more constraints on using the at least one of first or second codebooks comprise:

a first set of constraints for CSI reporting associated with single-user multiple-input multiple-output (SU-MIMO) operation, and

a second set of constraints for CSI reporting associated with multi-user multiple-input multiple-output (MU-MIMO) operation.