EP3874614A1

EP3874614A1 - Frequency domain channel state information compression

Info

Publication number: EP3874614A1
Application number: EP19877558.7A
Authority: EP
Inventors: Victor SERGEEV; Alexei Davydov; Bishwarup Mondal; Gregory V. Morozov; Dmitry DIKAREV
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2018-11-01
Filing date: 2019-10-29
Publication date: 2021-09-08
Also published as: CN112913155A; WO2020092340A1; CN112913155B; EP3874614A4

Abstract

Methods, systems, and circuitries are described for reporting precoding matrices to a base station. In one example a user equipment device (UE includes one or more processors configured to identify a codebook that specifies codebook parameters and precoding matrices. Each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients defined for different sets of frequency resources. The processors are configured to process a reference signal received from a base station to determine the codebook parameters of the reference signal; calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrices for use in downlink transmission from the base station to the UE; and report the PMI to the base station.

Description

FREQUENCY DOMAIN CHANNEL STATE INFORMATION COMPRESSION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Provisional Patent Application

Number 62/754,497 filed on November 1 , 2018, entitled“METHOD FOR

FREQUENCY DOMAIN CSI COMPRESSION,” and US Provisional Patent

Application Number 62/794,220 filed on January 18, 2019, entitled“FREQUENCY DOMAIN CHANNEL STATE INFORMATION (CSI) COMPRESSION,” both of which are incorporated herein by reference for all purposes.

BACKGROUND

[0002] Various examples generally may relate to the field of wireless

communications.

BRIEF DESCRIPTION OF THE FIGURES

[0003] Fig. 1 depicts an exemplary wireless communication network that includes a transmission/reception point (TRP) and a user equipment device (UE) performing downlink communication in accordance with some examples.

[0004] Fig. 2A depicts an exemplary representation of a precoding matrix.

[0005] Fig. 2B depicts an exemplary representation of a precoding matrix.

[0006] Fig. 3 depicts an exemplary representation of a precoding matrix.

[0007] Fig. 4 illustrates a functional block diagram of an exemplary UE wireless communication device in accordance with some examples.

[0008] Fig. 5 illustrates a functional block diagram of an exemplary TRP/base station wireless communication device in accordance with some examples.

DETAILED DESCRIPTION

[0009] The following detailed description refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of various examples. However, it will be apparent to those skilled in the art having the benefit of the present disclosure that the various aspects of the various examples may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the various examples with unnecessary detail.

For the purposes of the present document, the phrase“A or B” means (A), (B), or (A and B).

[0010] Fig. 1 illustrates a general overview of an exemplary downlink procedure for a wireless communication network that includes a base station 100 (e.g., eNB, gNB, TRP, and so on) and a user equipment device (UE) 120. An exemplary UE 120 is illustrated in Fig. 4 and an exemplary base station 100 is illustrated in Fig. 5. The base station 100 includes a baseband processor 1 10 that performs various functions for wireless communication. In the following description, if a base station is described as performing some function, it is to be understood that it is processor 1 10 that is performing the function. The UE 120 includes a baseband processor 130 that performs various functions for wireless communication. In the following description, if a UE is described as performing some function, it is to be understood that it is processor 130 that is performing the function.

[0011] As illustrated at A, to assist scheduling, link adaptation, precoding, and spatial multiplexing operations for downlink (DL) transmission the UE 120 monitors some predetermined channel state information (CSI) resources to receive CSI reference signals (CSI-RS). The UE 120 calculates several report quantities based on the received CSI-RS. As shown at B, the UE 120 transmits CSI feedback (e.g., CSI report) that includes the report quantities via physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH) to the base station 100.

[0012] There are three main components of a CSI report: the channel quality indicator, rank indicator, and the precoding matrix indicator. The channel quality indicator (CQI) contains information on the modulation and coding scheme

recommended by the user equipment (UE) for downlink (DL) transmission. The rank indicator (Rl) contains information on the number of spatial layers recommended by the UE for DL transmission. The precoding matrix indicator (PMI) contains information on the precoding matrix recommended by the UE for DL transmission. The PMI is a set of indexes corresponding to a specific precoding matrix from a specified finite set of precoding matrixes called a“codebook.” The Rl determines the rank of the precoding matrix. [0013] Returning to Fig. 1 , the base station 100 determines the PDSCH that should be used for downlink communication with the UE 120 based on the CSI report. As illustrated in C, the base station 100 transmits downlink control information (DCI) to the UE 120 to describe the PDSCH that will be used for downlink communication. The base station 100 then transmits downlink data using the PDSCH.

[0014] 5G NR and LTE physical layer support codebooks with higher spatial resolution based on linear combination of multiple mutually orthogonal digital Fourier transformation (DFT) beams. Such codebooks include 5G NR Type II Codebook, 5G NR Type II Port Selection Codebook, and LTE advance CSI codebook. The high spatial resolution of these codebooks is achieved by an increased number of bits required for Precoding Matrix Indicator (PMI) reporting.

[0015] Embodiments described herein are directed to solutions for decreasing the number of bits required for PMI reporting for codebooks with higher spatial resolution based on linear combination of DFT beams. The solutions presented in one or more embodiments presented herein are based on frequency domain compression utilizing correlation of beam combining coefficients in the frequency domain.

[0016] The existing solutions to decrease the number of bits required for reporting of PMI for codebooks with higher spatial resolution based on linear combination of multiple mutually orthogonal DFT beams are based on singular value decomposition (SVD) of space frequency matrix or a linear matrix transformation of space frequency matrix. There are several disadvantages of the existing solutions. One disadvantage is that many details of frequency domain channel state information (CSI) compression are missing, including a detailed definition of a space frequency matrix definition of basis for linear transformation and a quantization method of a compressed space frequency matrix.

Details of CSI reporting

[0017] Embodiments set forth herein describe details of a frequency domain CSI compression, including definition of a space frequency matrix, definition of a basis matrix with more detailed CSI components for frequency domain CSI compression, including definition of new CSI components, details of a quantization scheme for newly introduced CSI components, details of CSI reporting for the newly introduced CSI components, and a method of CSI quantization (hybrid time-frequency quantization of spatial coefficients). [0018] One or more embodiments set forth herein assist with decreasing the overhead of PMI reporting for Type II codebooks, which is beneficial for performance of 5G NR cellular systems. Embodiments set forth herein can be a part of the following features, if adopted by 3GPP RAN1 WG: 5G NR Type II Codebook (3GPP TS 38.214, 3GPP TS 38.212), 5G NR Type II Port Selection Codbook (3GPP TS 38.214, 3GPP TS 38.212), and LTE Advanced CSI codebook (3GPP TS 36.213, 3GPP TS 36.212).

Embodiments set forth herein can be specified in the following documents, if adopted by 3GPP RAN1 WG: 3GPP TS 38.214, 3GPP TS 38.212, 3GPP TS 36.213, and 3GPP TS 36.212.

DFT spatial beams

[0019] 5G NR and LTE codebooks are optimized for uniform rectangular planar antenna arrays with cross-polarized antennas and based on DFT spatial beams vi,_m defined by the following equation:

where N1 , N2 are numbers of cross-polarized antenna elements in first and second dimension respectively, 01 , 02 are oversampling factors in first and second dimension respectively, I = 0,1 ,...,(N101 - 1 ) is an index which determines spatial beam direction in first dimension, m = 0,1 ,...,(N202 - 1 ) is an index which determines spatial beam direction in second dimension.

[0020] There are also 5G NR and LTE codebooks, which are optimized for beamformed or precoded CSI reference signals (CSI-RS). In this case, port selection vectors bn are used instead of DFT spatial beams, where only n-th element of vector bn is equal to 1 and where other elements are equal to 0, n = 0,1 ,...,N_P, N_p being the number of CSI-RS ports with the same polarization.

5G NR and LTE codebooks

[0021] 5G NR and LTE codebooks can be divided in s groups: codebooks with normal spatial resolution based on selection of DFT spatial beam and codebooks with high spatial resolution based on linear combination DFT spatial beams. Codebooks with high spatial resolution based on linear combination of DFT spatial beams include the following 5G NR codebooks: Type II Codebook, Type II Port Selection Codebook. Codebooks with high spatial resolution based on linear combination of DFT spatial beams include the following LTE codebooks: advanced CSI codebook and codebooks with high spatial resolution based on beam linear combination

[0022] A precoding matrix of a codebook with high spatial resolution is constructed as a linear combination of L mutually orthogonal DFT spatial beams. A column of precoding matrix with beam combination structure is represented in (3) for rank 1 and (4) for rank 2.

where qi, q2, m, n2 indexes determines the set of L DFT spatial beams used in beam combination, i = 0,1 ,...,L-1 is the index of DFT spatial beam in the beam

w

combination, I = 1 ,2 is the index of layer, ^{1 1} * are the wideband amplitude coefficients, w

are the subband amplitude coefficients, ^Yi * are the phase coefficients,

nm

k = 0,1 ,...,(2-L - 1 ) is the index of coefficient in beam linear combination, ^l and„^l are the set of indexes determining wideband and subband amplitude coefficients respectively, ci is the set of indexes determining phase coefficients.

[0023] The number of beams in linear combination L can be configured by higher layers and/or specified in the specification of physical layer. The number of bits required for reporting and quantization scheme of wideband and subband amplitude coefficients and phase coefficients can be fixed configured by higher layers and/or specified in the

0

specification of physical layer. If the UE reports that ^ * , the subband amplitude coefficients and phase coefficients are not reported. 5G NR Type codebooks configuration

[0024] The number of spatial beams used in linear combination L is configured with the higher layer parameter numberOfBeams, L = {2,3,4}. The number of bits and quantization scheme for reporting of phase coefficients is configured with the higher layer parameter phaseAlphabetSize, where supported quantization schemes are QPSK and 8-PSK. The number of bits required for reporting of wideband amplitude coefficients is 3 bits. The number of bits required for reporting of sub-band amplitude coefficients is controlled by the higher layer parameter sub-bandAmplitude set to 'true' (1 bit) or 'false' (0 bits).

Overhead of PMI reporting for codebooks based on beam combining

[0025] The number of bits for PMI reporting for codebooks based on linear combination of DFT spatial beams can be calculated using (5).

Nbi_ts ~ beams + 2L R - N _amplWB + 2L R - N_SB N _amplSB + 2L R - N_SB N_phase

(5)

where Nbeams is the number of bits required for reporting of indexes of L mutually orthogonal beams, R is the rank value or number of layers, NamplWB is the number of bits required for reporting of a wideband amplitude coefficient, NSB is the number of sub-bands configured for CSI reporting, NamplWB is the number of bits required for reporting of a sub-band amplitude coefficient, Nphase is the number of bits required for reporting of a phase coefficient.

Soace frequency matrix

[0026] The equation for a precoding matrix (2, 3, 4) can be represented in simplified form with dual-stage structure (6).

W(k) = W_r W₂ (k) (ø)

where W(k) is the precoding matrix for rank R and frequency resource k with

dimensions 2N1 N2 c R, W1 is the matrix with wideband channel information with dimensions 2N1 N2 c 2L, W2(k) is the matrix with sub-band channel information for frequency resource k with dimensions 2L c R, k is the index of sub-band, k = 1 ,2,...,N. In one embodiment, frequency resource is a sub-band configured for CSI reporting. In order to do frequency domain compression, a precoding matrix can be represented in alternative form (7).

Y( = _r Y₂( where column k of Y(l) corresponds to layer I of precoding matrix for a frequency resource k, matrix Y(l) has dimensions 2N1 N2 c N, Y2(l) is space frequency matrix for spatial layer I with dimensions 2L c N, I = 1 ,2,...,R being the index of spatial layer.

Equations (6) and (7) are schematically represented in Fig. 2A and Fig. 2B respectively.

Compression of space frequency matrix

[0027] Overhead reduction of PMI reporting can be achieved by frequency domain or time domain compression of space frequency matrix Y2(l). Without compression of space frequency matrix, phase and amplitude of each coefficient of space frequency matrix are quantized and reported by the UE.

[0028] In one embodiment, the space frequency matrix can be compressed using linear transformation. The linear transformation corresponds to the equation (8) and it is schematically represented in Fig. 3.

Y₂ ( = z₁ (/) - z₂( ₍₈₎

where Zi (I) is the matrix with coefficients of linear transformation with dimensions 2L x M, å2(l) is the basis matrix of linear transformation with dimensions M c N. M is total number of vectors in the basis, N is number of frequency resources.

[0029] In one embodiment, M = MrO, where O - oversampling factor. In one embodiment, the oversampling factor is configured by higher layers. In one

embodiment, Mi is number of frequency resources. In one embodiment, the frequency resource is a sub-band configured for CSI reporting. In one embodiment, the frequency resource is a sub-band within the active bandwidth part. In one embodiment, the frequency resource is a physical resource block (PRB) configured for CSI reporting. In one embodiment, the frequency resource is a PRB in the active bandwidth part. In order to simplify further description linear transformation of space frequency matrix Y2(l) is represented by equation (9) as linear combination of basis vectors.

where z_m is the row of basis matrix å2(r) with index m or basis vector m, m = 1 ,2,...,M, S is the number of basis vectors in linear combination, g_sjj, s = 0,1 ,...,S-1 are the indexes of basis vectors in linear combination, a_{s j} are the coefficients of linear combination, i =

1 ,2,...,2L is the index of DFT beam and polarization, I = 1 ,2,...,R is the index of spatial layer. In one embodiment, a row of basis matrix of linear transformation Z2(r) is DFT vector Zm (10).

[0030] In one embodiment, the indexes of basis vectors in linear combination g_sjj are reported by a UE. In one embodiment, the indexes of basis vectors in linear combination g_sj are different for different DFT beams and different polarizations. In one embodiment, the indexes of basis vectors in linear combination g_{s, ,/}are same for different DFT beams and different polarizations g_sj = gs _j , i = 1 ,2,...,2L, j = 1 ,2,...,2L.

In one embodiment, the indexes of basis vectors in linear combination g_sj,i are same for a DFT beam and different polarizations g_s,u= <¾/_,/, i = 1 ,2,...,L, j = i + L. In one embodiment, the indexes of basis vectors in linear combination g_sjj are different for different layers.

[0031] In one embodiment, the indexes of basis vectors in linear combination g_sj are same for different layers g_sj = gs j, I = 1 ,2,...,R, j = 1 ,2,...,R. In one embodiment, the indexes of basis vectors in linear combination g_sj are reported by a UE separately for s = 0,1 ,...,S-1 . In one embodiment, the indexes of basis vectors in linear

combination g_sj are reported by a UE jointly for s = 0,1 ,...,S-1 by using index of combination G_/,/(1 1 ).

where g_sj,i increases as s increases, C(x,y) - combinatorial coefficients (e.g. table 1 ).

Table 1: Combinatorial coefficients C[x,y)

[0032] In one embodiment the number of basis vectors in linear combination S is configured by higher layers. In one embodiment S equals to M. In one embodiment S is a function of M. In one embodiment S equals to N. In one embodiment S is a function of N. In one embodiment, S is configured separately for different codebook rank value. In one embodiment, S is configured separately for different spatial layers.

Quantization of CSI components

[0033] In one embodiment the amplitudes and phases of coefficients of linear combination a_sjj are quantized and reported by a UE. In one embodiment the phases of coefficients of linear combination a_{s j} are quantized and reported by a UE. In one embodiment the phases of coefficients of linear combination a_sjj are quantized using set of values { ^{e}2 m/N} }_; m = 0,1 ,...,NPSK-1 . In one embodiment the quantization scheme of phases of coefficients of linear combination a_sjj is configured by higher layers. In one embodiment NPSK is configured by higher layers. In one embodiment the amplitudes of coefficients of linear combination a_sjj are quantized and reported by a UE. In one embodiment the amplitudes of coefficients of linear combination a_{s j} are

[-^,0]

quantized using of values { ²" }, n = 0,1 ,...,Na-2. In one embodiment amplitudes of

[—,0]

coefficients of linear combination a_{s ,i} are quantized using of values { ²" }, n =

0,1 ,...,Na-2.

[0034] In one embodiment the quantization scheme of phases of coefficients of linear combination a_sjj is configured by higher layers. In one embodiment N_a is configured by higher layers. In one embodiment, the leading coefficients of linear combination A_,/ are reported by a UE. In one embodiment, the index of leading coefficients is reported by a UE. In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of linear combination |a_{s, ,/} |/|A_,/| are reported by a UE. In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of j 2

linear combination |a_s,,_/ |/|A_/| are quantized using of values { ²" }, n = 0,1 ,...,N_a-2. In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of linear combination |a_s,,_/ |/|A_/| are quantized using of

[—,0]

values { ²" }, n = 0,1 ,...,Na-2.

[0035] In one embodiment, the phase of a product of a coefficient of linear combination and complex conjugate of leading coefficient of linear combination a_s,,_/ A ^* is reported by a UE. In one embodiment, the index of leading coefficients of linear combination is reported by a UE for each DFT beam and polarization and for each spatial layer. In one embodiment, the same index of leading coefficients of linear combination is reported by a UE for different DFT beams and polarizations.

CSI reporting

[0036] The 5G NR Type II codebook is reported via PUSCH. PUSCH based CSI reports comprise two parts: CSI part 1 and CSI part 2. CSI parts are separately encoded and transmitted using mutually orthogonal resource elements. The payload size of CSI part 1 is fixed for a given CSI configuration. The payload size of CSI part 2 depends on the content of CSI part 1 .

[0037] In one embodiment, the indexes of basis vectors in linear combination g_{s ,i} are reported in CSI part 1 . In one embodiment, the indexes of basis vectors in linear combination g_{s, ,/} are reported in CSI part 2. In one embodiment, the indexes of basis vectors in linear combination g_{s, ,/} are reported in CSI part 1 for 1 st spatial layer (1 = 1 ) and in CSI part 2 for 2nd spatial layer (I = 2).

[0038] In one embodiment, the amplitudes of coefficients of linear combination a_sjj are reported in CSI part 1 . In one embodiment, the amplitudes of coefficients of linear combination a_sjj are reported in CSI part 2. In one embodiment, the amplitudes of coefficients of linear combination a_sjj are reported in CSI part 1 for 1 st spatial layer (I = 1 ) and in CSI part 2 for 2nd spatial layer (I = 2).

[0039] In one embodiment, the number of coefficients of linear combination a_{s j} with non-zero amplitude is reported in CSI part 1 . In one embodiment, the number of coefficients of linear combination a_sjj with 0 amplitude is reported in CSI part 1 . In one embodiment, the number of coefficients of linear combination a_{s j} with non-zero amplitude is reported in CSI part 1 for spatial layer I. In one embodiment, the number of coefficients of linear combination a_s,u with 0 amplitude is reported in CSI part 1 for spatial layer I.

[0040] In one embodiment, the leading coefficients of linear combination A_,/ is reported in CSI part 1 . In one embodiment, the leading coefficients of linear combination A_/ is reported in CSI part 1 . In one embodiment, the leading coefficients of linear combination A/ is reported in CSI part 1 for 1 st spatial layer (1 = 1 ) and in CSI part 2 for 2nd spatial layer (I = 2).

[0041] In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of linear combination \a_sjj |/|A_/| are reported in CSI part 1 . In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of linear combination \a_{s ,i} |/|A_/| are reported in CSI part 2.

[0042] In one embodiment, the ratios of amplitudes of a coefficient of linear combination and amplitude of leading coefficient of linear combination \a_sjj |/|A_/| are reported in CSI part 1 for 1 st spatial layer (1 = 1 ) and in CSI part 2 for 2nd spatial layer (I = 2).

Hybrid time-freauencv quantization of spatial coefficients

[0043] In one embodiment, the space frequency matrix Y2(l) is reported by a UE using hybrid time-frequency quantization. In one embodiment, s subset of rows of space-frequency matrix { ^y'°} is quantized and reported as linear combination of basis v⁽

vectors (9) and other rows of space-frequency matrix are quantized and reported using phase and/or amplitude quantization and reporting of each element of this rows.

In one embodiment, the subset of rows of space frequency matrix { ^y'° °} is determined based on average amplitude of elements of rows of space frequency matrix. In one

( ) embodiment, the number of rows of space frequency matrix in the subset { ^y- } is configured by higher layers.

Reporting of coefficients associated with the strongest beam/polarization

[0044] Since SVD vectors and Eigen vectors are defined up to multiplication by a unit-phase factor, the performance of Ml MO system is the same if precoder vectors for kth sub-band is V(k) or e^j(pV(k), where e^j(p is complex exponent with arbitrary phase. This property can be used in order to achieve better performance frequency domain CSI compression and/or reduce reporting overhead.

[0045] Hence, each column of space frequency matrix Y2(l) can be multiplied by a complex number with arbitrary phase and unit amplitude. In one embodiment UE multiplies column kth column of matrix Y2(l) by q(k)^*, k = 1 ,2,...,N. In one embodiment q(k) = c(k)/|c(k)|, where c(k) is the row of space frequency matrix Y2 ) associated with the strongest DFT beam/polarization (DFT beam/polarization with the highest average or wideband power). After such operation frequency-domain coefficients associated with the strongest DFT beam/polarization are real numbers |c(k)|. Time-domain coefficients associated with the strongest DFT beam/polarization C(m), m = 1 ,2,...,M, are derived at the UE by DFT with certain oversampling factor of frequency-domain coefficients associated with the strongest DFT beam/polarization |c(k)|.

[0046] It can be a priory assumed that frequency-domain coefficients associated with the strongest DFT beam/polarization are real to reduce overhead or improve

performance of frequency-domain compression. If frequency-domain coefficients are real numbers, time-domain coefficients (coefficients after multiplication by DFT matrix) have symmetry property and the following equation is valid.

C(m) = C^*({(-m + l)modM} + l) ^₂₎

[0047] As it can be seen from the equation (12), some time-domain coefficients can be derived from other time domain coefficients. In one embodiment a time-domain coefficient associated with the strongest DFT beam/polarization are divided into two sets C1 and C2. In one embodiment C1 includes coefficients C(m) with indexes m <

(M/2 + 1 ) and C2 includes remaining coefficients C(m). In one embodiment a subset of coefficients from C1 is reported by the UE. In one embodiment coefficients from C2 are derived based on coefficients from C1 using a predefined equation. In one example equation (12) is used to derive coefficients from C2 based on coefficients from C1 . In one embodiment a space frequency matrix Y2 ) is reconstructed using equation (9) considering time-domain coefficients from C2 derived based on the reported time- domain coefficients from C1 .

[0048] Fig. 4 illustrates a user device 120 (see also Figs. 1 and 2) in accordance with an aspect. The user device 120 may be a mobile device or a user equipment (UE) in some aspects. The device 120 is configured to transmit and receive RF signals and includes an application processor 405, baseband processor 130 (also referred to as a baseband module), radio front end module (RFEM) 415 (also referred to as a radio interface), memory 420, connectivity module 425, near field communication (NFC) controller 430, audio driver 435, camera driver 440, touch screen 445, display driver 450, sensors 455, removable memory 460, power management integrated circuit (PMIC) 465 and smart battery 470.

[0049] In some aspects, application processor 405 may include, for example, one or more CPU cores and one or more of cache memory, low drop-out voltage regulators (LDOs), interrupt controllers, serial interfaces such as serial peripheral interface (SPI), inter-integrated circuit (I2C) or universal programmable serial interface module, real time clock (RTC), timer-counters including interval and watchdog timers, general purpose input-output (10), memory card controllers such as secure digital / multi-media card (SD/MMC) or similar, universal serial bus (USB) interfaces, mobile industry processor interface (Ml PI) interfaces and Joint Test Access Group (JTAG) test access ports.

[0050] In some aspects, baseband module 130 may be implemented, for example, as a solder-down substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board, and/or a multi-chip module containing two or more integrated circuits.

[0051] Fig. 5 illustrates an example base station or gNB/TRP/eNB 100 (See also Figs. 1 and 2) in accordance with an aspect. The eNB 100 is configured to transmit and receive RF signals and may include one or more of application processor 505, baseband modules 1 10 (also referred to as baseband processors), one or more radio front end modules 515 (also referred to as a radio interface), memory 520, power management circuitry 525, power tee circuitry 530, network controller 535, network interface connector 540, satellite navigation receiver module 545, and user interface 550.

[0052] In some aspects, application processor 505 may include one or more CPU cores and one or more of cache memory, low drop-out voltage regulators (LDOs), interrupt controllers, serial interfaces such as SPI, I2C or universal programmable serial interface module, real time clock (RTC), timer-counters including interval and watchdog timers, general purpose IO, memory card controllers such as SD/MMC or similar, USB interfaces, MIPI interfaces and Joint Test Access Group (JTAG) test access ports.

[0053] In some aspects, baseband processor 1 10 may be implemented, for example, as a solder-down substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board or a multi-chip module containing two or more integrated circuits.

[0054] In some aspects, memory 520 may include one or more of volatile memory including dynamic random access memory (DRAM) and/or synchronous dynamic random access memory (SDRAM), and nonvolatile memory (NVM) including high speed electrically erasable memory (commonly referred to as Flash memory), phase change random access memory (PRAM), magnetoresistive random access memory (MRAM) and/or a three-dimensional crosspoint memory. Memory 520 may be implemented as one or more of solder down packaged integrated circuits, socketed memory modules and plug-in memory cards.

[0055] In some aspects, power management integrated circuitry 525 may include one or more of voltage regulators, surge protectors, power alarm detection circuitry and one or more backup power sources such as a battery or capacitor. Power alarm detection circuitry may detect one or more of brown out (under-voltage) and surge (over-voltage) conditions.

[0056] In some aspects, power tee circuitry 530 may provide for electrical power drawn from a network cable to provide both power supply and data connectivity to the base station radio head 100 using a single cable.

[0057] In some aspects, network controller 535 may provide connectivity to a network using a standard network interface protocol such as Ethernet. Network connectivity may be provided using a physical connection which is one of electrical (commonly referred to as copper interconnect), optical or wireless.

[0058] In some aspects, satellite navigation receiver module 545 may include circuitry to receive and decode signals transmitted by one or more navigation satellite constellations such as the global positioning system (GPS), Globalnaya

Navigatsionnaya Sputnikovaya Sistema (GLONASS), Galileo and/or BeiDou. The receiver 545 may provide data to application processor 505 which may include one or more of position data or time data. Application processor 505 may use time data to synchronize operations with other radio base stations.

[0059] In some aspects, user interface 550 may include one or more of physical or virtual buttons, such as a reset button, one or more indicators such as light emitting diodes (LEDs) and a display screen.

[0060] While the invention has been illustrated and described with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular regard to the various functions performed by the above described

components or structures (assemblies, devices, circuits, circuitries, systems, etc.), the terms (including a reference to a "means") used to describe such components are intended to correspond, unless otherwise indicated, to any component or structure which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary

implementations of the invention.

[0061] Various illustrative logics, logical blocks, modules, circuitries, and circuits described in connection with aspects disclosed herein can 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, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform functions described herein. A general-purpose processor can be a microprocessor, but, in the alternative, processor can be any conventional processor, controller, microcontroller, or state machine.

[0062] The above description of illustrated embodiments of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such embodiments and examples, as those skilled in the relevant art can recognize.

[0063] In this regard, while the disclosed subject matter has been described in connection with various embodiments and corresponding Figs, where applicable, it is to be understood that other similar embodiments can be used or modifications and additions can be made to the described embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims below.

[0064] In the present disclosure like reference numerals are used to refer to like elements throughout, and wherein the illustrated structures and devices are not necessarily drawn to scale. As utilized herein, terms“module”,“component,”“system,” “circuit,”“circuitry,”“element,”“slice,” and the like are intended to refer to a computer- related entity, hardware, software (e.g., in execution), and/or firmware. For example, circuitry or a similar term can be a processor, a process running on a processor, a controller, an object, an executable program, a storage device, and/or a computer with a processing device. By way of illustration, an application running on a server and the server can also be circuitry. One or more circuitries can reside within a process, and circuitry can be localized on one computer and/or distributed between two or more computers. A set of elements or a set of other circuitry can be described herein, in which the term“set” can be interpreted as“one or more.”

[0065] As another example, circuitry or similar term can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, in which the electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processors. The one or more processors can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, circuitry can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include field gates, logical

components, hardware encoded logic, register transfer logic, one or more processors therein to execute software and/or firmware that confer(s), at least in part, the

functionality of the electronic components.

[0066] It will be understood that when an element is referred to as being“electrically connected” or“electrically coupled” to another element, it can be physically connected or coupled to the other element such that current and/or electromagnetic radiation can flow along a conductive path formed by the elements. Intervening conductive, inductive, or capacitive elements may be present between the element and the other element when the elements are described as being electrically coupled or connected to one another. Further, when electrically coupled or connected to one another, one element may be capable of inducing a voltage or current flow or propagation of an electro magnetic wave in the other element without physical contact or intervening components. Further, when a voltage, current, or signal is referred to as being“applied” to an element, the voltage, current, or signal may be conducted to the element by way of a physical connection or by way of capacitive, electro-magnetic, or inductive coupling that does not involve a physical connection. [0067] Use of the word exemplary is intended to present concepts in a concrete fashion. The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of examples. As used herein, the singular forms“a,”“an” and“the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,”“comprising,”“includes” and/or“including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

[0068] For one or more examples, at least one of the components set forth in one or more of the preceding Figs may be configured to perform one or more operations, techniques, processes, and/or methods as set forth in the example section below. For example, the baseband circuitry as described above in connection with one or more of the preceding Figs may be configured to operate in accordance with one or more of the examples set forth below. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding Figs may be configured to operate in accordance with one or more of the examples set forth below in the example section.

EXAMPLES

[0069] Example 1 is an apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors. The one or more processors are configured to identify a codebook that specifies codebook parameters and precoding matrices, wherein each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients defined for different sets of frequency resources; process a reference signal received from a base station to determine the codebook parameters of the reference signal; calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrices for use in downlink transmission from the base station to the UE; and report the PMI to the base station.

[0070] Example 2 includes the subject matter of example 1 , including or omitting optional elements, wherein the set of frequency resources comprises a subband configured for CSI reporting, a subband in an active bandwidth part, a physical resource block configured for CSI reporting, or a physical resource block within the active bandwidth part.

[0071] Example 3 includes the subject matter of any one of examples 1 -2, including or omitting optional elements, wherein the coefficients for each spatial beam and set of frequency resources form a vector y that is a linear combination of a subset of basis vectors, wherein each basis vector is a column of a discrete Fourier transform matrix.

[0072] Example 4 includes the subject matter of example 3, including or omitting optional elements, wherein a total number of basis vectors is determined from a number of frequency resources in the set of frequency resources.

[0073] Example 5 includes the subject matter of example 4, including or omitting optional elements, wherein a total number of basis vectors is determined based on a product of the number of frequency resources in the set of frequency resources and an oversampling factor of the discrete Fourier transform matrix.

[0074] Example 6 includes the subject matter of example 3, including or omitting optional elements, wherein a total number of basis vectors or a number of basis vectors in the subset of basis vectors is configured by higher layers.

[0075] Example 7 includes the subject matter of example 3, including or omitting optional elements, wherein a number of basis vectors in the subset of basis vectors is configured by higher layers for each spatial layer or for each rank.

[0076] Example 8 includes the subject matter of example 3, including or omitting optional elements, wherein a number of basis vectors in the subset of basis vectors equals a total number of basis vectors or a number of frequency resources in the set of frequency resources.

[0077] Example 9 is an apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors. The one or more processors are configured to: identify a codebook that specifies codebook parameters and precoding matrices, wherein each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients of linear combination defined for different sets of frequency resources, wherein the coefficients for each spatial beam and set of frequency resources form a vector y that is a linear combination of a subset of basis vectors, further wherein each basis vector is a column of an discrete Fourier transform matrix and is identified by a unique value of a basis vector index; process a reference signal received from a base station to determine the codebook parameters of the reference signal; calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI includes the coefficients of linear combination and

corresponding basis vector indexes for a selected subset of basis vectors defining a desired linear combination of spatial beams for use in downlink transmission from the base station to the UE; and report the PMI to the base station.

[0078] Example 10 includes the subject matter of example 9, including or omitting optional elements, wherein the basis vector indexes for the selected subset of basis vectors are different for different spatial layers and spatial beams.

[0079] Example 1 1 includes the subject matter of example 9, including or omitting optional elements, wherein the basis vector indexes for the selected subset of basis vectors are the same for different spatial layers or different spatial beams.

[0080] Example 12 includes the subject matter of example 9, including or omitting optional elements, wherein the one or more processors are configured to report the basis vector indexes in the selected subset of basis vectors jointly using an index of combination.

[0081] Example 13 includes the subject matter of any one of examples 9-12, including or omitting optional elements, wherein the one or more processors are configured to quantize coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and report the coefficients to the base station.

[0082] Example 14 includes the subject matter of example 13, including or omitting optional elements, wherein the one or more processors are configured to: quantize phases of the coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and report the phases of the coefficients to the base station.

[0083] Example 15 includes the subject matter of example 14, including or omitting optional elements, wherein the one or more processors are configured to: quantize amplitudes of the coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and report the amplitudes of the coefficients to the base station.

[0084] Example 16 includes the subject matter of example 13, including or omitting optional elements, wherein the one or more processors are configured to: quantize a leading coefficient of linear combination of the basis vector indexes in the selected subset of basis vectors; and report the leading coefficient to the base station.

[0085] Example 17 includes the subject matter of example 16, including or omitting optional elements, wherein the one or more processors are configured to report an index of the leading coefficient to the base station.

[0086] Example 18 includes the subject matter of example 16, including or omitting optional elements, wherein the one or more processors are configured to: quantize ratios of amplitudes of each coefficient of linear combination and an amplitude of a leading coefficient of linear combination; and report the ratios to the base station.

[0087] Example 19 includes the subject matter of example 16, including or omitting optional elements, wherein the one or more processors are configured to: quantize a phase of a product of each coefficient of linear combination and complex conjugate of the leading coefficient of linear combination; and report the phase to the base station.

[0088] Example 20 includes the subject matter of example 9, including or omitting optional elements, wherein the one or more processors are configured to: identify a strongest spatial beam; and report a linear combination of a subset of basis vectors corresponding to the identified spatial beam to the base station.

[0089] Example 21 includes the subject matter of example 9, including or omitting optional elements, wherein elements of vector y are real numbers.

[0090] Example 22 includes the subject matter of example 21 , including or omitting optional elements, wherein: the vector y is expressed as a vector c having elements divided into a set C1 and a set C2, wherein each element from C2 is a complex conjugate of a corresponding element of set C1 ; and the one or more processors are configured to report a subset of elements from C1 to the base station.

[0091] Example 23 includes the subject matter of example 22, including or omitting optional elements, wherein the one or more processors are configured to: derive a subset of elements of C2 based on the subset of elements of C1 reported to the base station; and report the subset of elements of C2 to the base station.

[0092] Example 24 is an apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors. The one or more processors are configured to: identify a codebook that specifies codebook parameters and precoding matrices, wherein each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients of linear combination defined for different sets of frequency resources, wherein the coefficients for each spatial beam and set of frequency resources form a vector y that is a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index; process a reference signal received from a base station to determine the codebook parameters of the reference signal; calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI includes the coefficients of linear combination and

corresponding basis vector indexes for a selected subset of basis vectors defining a desired linear combination of spatial beams for use in downlink transmission from the base station to the UE; and report the PMI to the base station in a CSI report having a first part and a second part.

[0093] Example 25 includes the subject matter of example 24, including or omitting optional elements, wherein the first part includes a number of coefficients of linear combination with non-zero amplitude.

[0094] Example 26 includes the subject matter of example 24, including or omitting optional elements, wherein the second part includes phases of the coefficients of linear combination, amplitudes of the coefficients of linear combination, an amplitude of a leading coefficient of linear combination, and indexes of basis vectors in the subset of basis vectors.

[0095] Any of the above described examples may be combined with any other example (or combination of examples), unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of examples to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various examples.

Claims

CLAIMS We claim:

1 . An apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors configured to:

identify a codebook that specifies codebook parameters and precoding matrices, wherein each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients defined for different sets of frequency resources;

process a reference signal received from a base station to determine the codebook parameters of the reference signal;

calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrices for use in downlink transmission from the base station to the UE; and

report the PMI to the base station.

2. The apparatus of claim 1 , wherein the set of frequency resources comprises a subband configured for CSI reporting, a subband in an active bandwidth part, a physical resource block configured for CSI reporting, or a physical resource block within the active bandwidth part.

3. The apparatus of any one of claims 1 -2, wherein the coefficients for each spatial beam and set of frequency resources form a vector y that is a linear combination of a subset of basis vectors, wherein each basis vector is a column of a discrete Fourier transform matrix.

4. The apparatus of claim 3, wherein a total number of basis vectors is determined from a number of frequency resources in the set of frequency resources.

5. The apparatus of claim 4, wherein a total number of basis vectors is determined based on a product of the number of frequency resources in the set of frequency resources and an oversampling factor of the discrete Fourier transform matrix.

6. The apparatus of claim 3, wherein a total number of basis vectors or a number of basis vectors in the subset of basis vectors is configured by higher layers.

7. The apparatus of claim 3, wherein a number of basis vectors in the subset of basis vectors is configured by higher layers for each spatial layer or for each rank.

8. The apparatus of claim 3, wherein a number of basis vectors in the subset of basis vectors equals a total number of basis vectors or a number of frequency resources in the set of frequency resources.

9. An apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors configured to:

identify a codebook that specifies codebook parameters and precoding matrices, wherein each column of the precoding matrices corresponds to a spatial layer and is constructed by linear combination of spatial beams with each spatial beam having coefficients of linear combination defined for different sets of frequency resources, wherein the coefficients for each spatial beam and set of frequency resources form a vector y that is a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index;

calculate, based on the codebook parameters, a precoding matrix indicator (PMI), wherein the PMI includes the coefficients of linear combination and

corresponding basis vector indexes for a selected subset of basis vectors defining a desired linear combination of spatial beams for use in downlink transmission from the base station to the UE; and

report the PMI to the base station.

10. The apparatus of claim 9, wherein the basis vector indexes for the selected subset of basis vectors are different for different spatial layers and spatial beams.

1 1 . The apparatus of claim 9, wherein the basis vector indexes for the selected subset of basis vectors are the same for different spatial layers or different spatial beams.

12. The apparatus of claim 9, wherein the one or more processors are configured to report the basis vector indexes in the selected subset of basis vectors jointly using an index of combination.

13. The apparatus of any of claims 9-12, wherein the one or more processors are configured to:

quantize coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and

report the coefficients to the base station.

14. The apparatus of claim 13, wherein the one or more processors are configured to:

quantize phases of the coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and

report the phases of the coefficients to the base station.

15. The apparatus of claim 14, wherein the one or more processors are configured to:

quantize amplitudes of the coefficients of linear combination of the basis vector indexes in the selected subset of basis vectors; and

report the amplitudes of the coefficients to the base station.

16. The apparatus of claim 13, wherein the one or more processors are configured to:

quantize a leading coefficient of linear combination of the basis vector indexes in the selected subset of basis vectors; and

report the leading coefficient to the base station.

17. The apparatus of claim 16, wherein the one or more processors are configured to report an index of the leading coefficient to the base station.

18. The apparatus of claim 16, wherein the one or more processors are configured to:

quantize ratios of amplitudes of each coefficient of linear combination and an amplitude of a leading coefficient of linear combination; and

report the ratios to the base station.

19. The apparatus of claim 16, wherein the one or more processors are configured to:

quantize a phase of a product of each coefficient of linear combination and complex conjugate of the leading coefficient of linear combination; and

report the phase to the base station.

20. The apparatus of claim 9, wherein the one or more processors are configured to: identify a strongest spatial beam; and

report a linear combination of a subset of basis vectors corresponding to the identified spatial beam to the base station.

21 . The apparatus of claim 9, wherein elements of vector y are real numbers.

22. The apparatus of claim 21 , wherein:

the vector y is expressed as a vector c having elements divided into a set C1 and a set C2, wherein each element from C2 is a complex conjugate of a corresponding element of set C1 ;and

the one or more processors are configured to report a subset of elements from C1 to the base station.

23. The apparatus of claim 22, wherein the one or more processors are configured to:

derive a subset of elements of C2 based on the subset of elements of C1 reported to the base station; and

report the subset of elements of C2 to the base station.

24. An apparatus for a user equipment device (UE), comprising baseband circuitry having a radio frequency (RF) interface configured to transmit and receive RF signals, and one or more processors configured to:

report the PMI to the base station in a CSI report having a first part and a second part.

25. The apparatus of claim 24, wherein the first part includes a number of coefficients of linear combination with non-zero amplitude.

26. The apparatus of claim 24, wherein the second part includes phases of the coefficients of linear combination, amplitudes of the coefficients of linear combination, an amplitude of a leading coefficient of linear combination, and indexes of basis vectors in the subset of basis vectors.