WO2018031082A1

WO2018031082A1 - Discrete fourier transform (dft) codebook and feedback schemes

Info

Publication number: WO2018031082A1
Application number: PCT/US2017/028925
Authority: WO
Inventors: Oner Orhan; Wook Bong Lee; Yang-Seok Choi; Alexei Davydov; Shilpa Talwar
Original assignee: Intel Corporation
Priority date: 2016-08-11
Filing date: 2017-04-21
Publication date: 2018-02-15

Abstract

Technology for a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks is disclosed. The UE can decode a channel state information reference signal (CSI-RS) received from a base station. The UE can estimate a channel vector between the UE and the base station based on the CSI-RS. The UE can select a codebook index from a DFT codebook. The DFT codebook can be configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna. The UE can encode feedback that includes the codebook index for transmission to the base station.

Description

DISCRETE FOURIER TRANSFORM (DFT) CODEBOOK AND

FEEDBACK SCHEMES

BACKGROUND

[0001] Wireless mobile communication technology uses various standards and protocols to transmit data between a node (e.g., a transmission station) and a wireless device (e.g., a mobile device). Some wireless devices communicate using orthogonal frequency-division multiple access (OFDMA) in a downlink (DL) transmission and single carrier frequency division multiple access (SC-FDMA) in uplink (UL). Standards and protocols that use orthogonal frequency-division multiplexing (OFDM) for signal transmission include the third generation partnership project (3 GPP) long term evolution (LTE) Release 8, 9, 10, 11, 12 and 13, the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard (e.g., 802.16e, 802.16m), which is commonly known to industry groups as WiMAX (Worldwide interoperability for Microwave Access), and the IEEE 802.11 standard, which is commonly known to industry groups as WiFi.

[0002] In 3GPP radio access network (RAN) LTE systems (e.g., Release 13 and earlier), the node can be a combination of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), which communicates with the wireless device, known as a user equipment (UE). The downlink (DL) transmission can be a communication from the node (e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL) transmission can be a communication from the wireless device to the node.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Features and advantages of the disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the disclosure; and, wherein:

[0004] FIG. 1 illustrates an antenna model in accordance with an example;

[0005] FIG. 2 illustrates an antenna subarray in accordance with an example; [0006] FIG. 3 illustrates an antenna subarray structure in accordance with an example;

[0007] FIG. 4 illustrates a performance comparison for a novel d screte Fourier transform (DFT) codebook in accordance with an example;

[0008] FIG. 5 illustrates an antenna array for a two-sector base station in accordance with an example;

[0009] FIG. 6 illustrates a performance comparison for a novel discrete Fourier transform (DFT) codebook and an auto-correlation matrix based feedback scheme in accordance with an example;

[0010] FIG. 7 illustrates a performance comparison for a novel discrete Fourier transform (DFT) codebook and no feedback scheme in accordance with an example;

[0011] FIG. 8 illustrates a multi-beam transmission from a base station in accordance with an example;

[0012] FIG. 9 illustrates a performance comparison for discrete Fourier transform (DFT) based feedback for multi-beam transmission in accordance with an example;

[0013] FIG. 10 depicts functionality of a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks in accordance with an example;

[0014] FIG. 11 depicts functionality of a base station operable to process codebook indexes in discrete Fourier transform (DFT) codebooks received from a user equipment (UE) in accordance with an example;

[0015] FIG. 12 depicts a flowchart of a machine readable storage medium having instructions embodied thereon for selecting codebook indexes from discrete Fourier transform (DFT) codebooks in accordance with an example;

[0016] FIG. 13 illustrates an architecture of a wireless network in accordance with an example;

[0017] FIG. 14 illustrates a diagram of a wireless device (e.g., UE) in accordance with an example;

[0018] FIG. IS illustrates interfaces of baseband circuitry in accordance with an example; and [0019] FIG. 16 illustrates a diagram of a wireless device (e.g., UE) in accordance with an example.

[0020] Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the technology is thereby intended.

DETAILED DESCRIPTION

[0021] Before the present technology is disclosed and described, it is to be understood that this technology is not limited to the particular structures, process actions, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular examples only and is not intended to be limiting. The same reference numerals in different drawings represent the same element. Numbers provided in flow charts and processes are provided for clarity in illustrating actions and operations and do not necessarily indicate a particular order or sequence.

EXAMPLE EMBODIMENTS

[0022] An initial overview of technology embodiments is provided below and then specific technology embodiments are described in further detail later. This initial summary is intended to aid readers in understanding the technology more quickly but is not intended to identify key features or essential features of the technology nor is it intended to limit the scope of the claimed subject matter.

[0023] In 3GPP LTE systems, discrete Fourier transform (DFT) based codebooks with uniform antenna spacing based beamforming has been adopted as a closed loop multiple- input multiple-output (MIMO) scheme. A base station can transmit a channel state information reference signal (CSI-RS) to a user equipment (UE), and the UE can measure a channel vector (g) between the base station and the UE. The UE can determine a preferred matrix index (PMI) to maximize signal-to-noise ratio (SNR).

[0024] In one example, with respect to a rank-1 transmission (for beam forming), a quantization scheme can be defined as follows: = Q(g) = c_m, wherein g is the channel

vector between the base station and the UE, Q(g) represents a quantization function for g, and c_m represents a m'th codeword from a codebook. In one example, m =

arg max|g^Tc_fc|, wherein m represents a codeword index, g^T represents a transpose of g, and c_k represents a k'th codeword from a codebook.

[0025] In one example, the codebook (c_fc) can be represented as follows: c_k =

wherein N represents a number of antennas

at the base station, and k represents a codebook index. The UE can select a DFT codebook index, and the UE can feed back the DFT codebook index to the base station. The base station can perform precoding based on the DFT codebook index.

[0026] In one example, the quantization scheme can be designed for fully digital MIMO system with a reduced number of antennas. As the number of antennas increases, hybrid beamforming can be utilized to decrease power consumption and increase coverage range.

[0027] FIG. 1 illustrates an example of a base station antenna model. The base station antenna model can be a uniform rectangular panel array. The uniform rectangular panel array can include M_gN_g panels, wherein M_g represents a number of panels in a column, and N_g represents a number of panels in a row. An inter-panel distance in a vertical direction (or vertical domain) can be represented by d_{g V}, and an inter-panel distance in a horizontal direction (or horizontal domain) can be represented by d_{g H}, On each panel, there can be N antennas in the vertical direction and M antennas in the horizontal direction, wherein N and M are integers. An inter-element spacing in the vertical direction can be represented by d_v, and an inter-element spacing in the horizontal direction can be represented by d_H. In addition, there can be a total of NMM_gN_g antennas per polarization. [0028] As shown in FIG. 1, inter antenna element distances can be different from each other, and inter panel distances can be different from each other. In other words, due to the panel structure, distances between the antennas can vary, and distances between individual panels can vary. In addition, each radio frequency (RF) chain in the panel can be connected to multiple antennas with a phase shifter (e.g., by using hybrid

beamforming). [0029] In the present technology, various novel quantization and feedback schemes are described. These novel quantization and feedback schemes can be utilized along with existing DFT based quantization techniques for a base station with a rectangular panel array. The novel quantization and feedback schemes can account for various inter panel and antenna element distances, as well as sectors, at the base station. The novel quantization and feedback schemes can increase throughput (e.g., SNR) as compared to existing DFT based codebooks.

[0030] In the present technology, the novel quantization and feedback schemes can be advantageous over previous DFT based schemes. For example, the novel quantization and feedback schemes can consider that: the base station has a rectangular panel array and serves a single UE, inter antenna element and inter panel distances can be different at the base station, and an antenna array for analog beamforming can have an arbitrary size.

[0031] In the present technology, the UE can update a DFT based codebook according to the base station antenna array. The UE can feed back a codebook index (i.e., only an index from one codebook). The UE can utilize a feedback scheme in which the UE receives signals from different sectors of the base station or from multiple base stations. Alternatively, the UE can utilize a feedback scheme that reduces an effect of coarse quantization at the codebook. In another alternative, the UE can utilize a feedback scheme which considers a multi-beam transmission at the base station. In addition, a scheme for analog beamforming that reduces a feedback size can be utilized.

[0032] In the present technology, the novel quantization and feedback schemes can be utilized for MIMO within a cell and with respect to a rectangular panel array. The novel quantization and feedback schemes can take into account inter panel and antenna element distances, analog beamforming, and properties of an effective channel. In addition, the novel quantization and feedback schemes can be expected to have higher average throughput and a lower feedback size restriction as compared to previous DFT based codebooks.

[0033] FIG. 2 illustrates an example of an antenna subarray. As previously explained, a uniform rectangular panel array can include M_gN_g panels. Each panel can be partitioned into A_H x A_v subarray (s), wherein A_H represents a number of antennas in a horizontal direction and A_v represents a number of antennas in a vertical direction. Each panel can be partitioned into the A_H x A_v subarray for analog beamforming. In addition, each antenna subarray for analog beamforming can be connected to one RF chain for digital processing. Therefore, a given panel can have subarrays and RF chains per

polarization.

[0034] FIG. 3 illustrates an example of an antenna subarray structure. As shown, a distance between antenna subarrays on a given panel in a vertical direction can be represented by d_{s V}, wherein d_{s V} = A_vd_v. A distance between antenna subarrays on a given panel in a horizontal direction can be represented by d_{s H}, wherein d_{s H} = A_Hd_H. A distance between adjacent antenna subarrays between two panels in the vertical direction can be represented by d_sgy, wherein d_{sg V} = d_{g V}— (M— A_v)d_v. A distance between adjacent antenna subarrays between two panels in the horizontal direction can be represented by d_{sg H}, wherein d_{sg H} = d_{g H}— (N— A_H)d_H.

[0035] In one example, with respect to MIMO codebook/quantization techniques, M_rj can represent a number of RF chains in the horizontal direction at the base station, and N_rj can represent a number of RF chains in the vertical direction at the base station. Here,

In other words, there can be RF chains in the

horizontal direction at the base station and RF chains in the vertical direction

at the base station. There can also be one RF chain at the UE.

[0036] In one example, a rank-1 transmission (for beam forming) can be extended to multiple RF chains when an appropriate receiver filter is applied. In addition, the rank-1 transmission can be extended to a multi-rank transmission using a corresponding receiver filter and treating each effective channel as a rank-1 transmission.

[0037] In one example, the base station and the UE can perform a sector sweep procedure. The UE can feed back an optimal analog beamforming direction to the base station. Based on this received feedback, the base station and UE can perform analog beamforming using phase shifters. Each analog beamforming array per RF chain can select a beamforming direction from a common analog codebook.

[0038] In one example, the analog codebook ( A_i,j ) can be represented as follows: A_i,j = A_h A_v, wherein i = 1, ... , V and j = 1, ... , H. Here, A_h represents an analog codebook in the horizontal direction, and A_v represents an analog codebook in the vertical direction. In addition, i can represent a codebook index in the vertical direction for beamforming, wherein V represents an integer in the vertical direction, and j represents a codebook index in the horizontal direction for beamforming, wherein H represents an integer in the horizontal direction.

[0039] In one example, the following equations can be derived:

wherein φ _i represents a

zenith angle of departure, 9_j represents an azimuth angle of departure, λ represents a radio wavelength, and T represents a transpose function.

[0040] In one example, after applying analog beamforming, an effective channel matrix

T T

(g(f)) can be obtained, and the effective channel matrix (g(f)) can be 1 x N_rfM_rf. Here, / can represent a subcarrier or tone index. In addition, = vec(G(f)), wherein is N_rf x M_rf and vec(-) is a vectorization operation. [0041] In one example, an input-output relation can be written as: y = (g(f))^H wx + n, wherein y represents a received signal, w represents a N_rfM_rf x 1 digital beamforming vector, x represents input data, and n represents noise.

[0042] In one example, after analog beamforming, the base station can send a channel state information reference signal (CSI-RS) to the UE. Based on the CSI-RS, the UE can estimate the channel, g(f), between the base station and the UE.

[0043] In one example, the UE can select a DFT codebook index from a predefined DFT codebook, and the UE can feedback the DFT codebook index to the base station. The UE can feedback the DFT codebook index via a narrowband transmission or a wideband transmission. For the narrowband transmission, a quantized channel (g) can be represented by g = Q(g), wherein Q(g) represents a quantization function. For the wideband transmission, a largest eigenvalue of R_k can be determined, wherein R_k represents an auto correlation matrix of the channel, and can be represented as follows: Here, N_FFT represents a Fast-Fourier Transform (FFT)

size, and H represents a Hermitian function. In addition, v can denote a corresponding eigenvector for a largest eigenvalue, and a quantized channel (g) can be obtained as follows wherein Q(-) represents a quantization function.

[0044] In one example, as a performance matrix, a receive SNR can be maximized in accordance with the following:

[0045] In one example, with respect to channel quantization, a codebook for limited feedback in the horizontal direction can be represented by C_{H LH}, and C_{H LH} =

wherein L_h represents a codebook size in the horizontal direction. Similarly, a codebook for limited feedback in the vertical direction can be represented by C_VIL_V, and C_{V LV} = [c_{v l}, c_{v 2}, ... , C_V L_V}, wherein L_V represents a codebook size in the vertical direction.

[0046] In one configuration, a two-stage DFT based quantization scheme can be defined for within a sector at the base station. If each panel has a single RF chain, then a distance between subarrays can be d_{sg V} and d_{sg H}, wherein d_{sg V} = d_{g V} and d_sg,H = d_g,H . Then, the DFT codebook, which can include a DFT codebook in the vertical direction (c_v,k) and a DFT codebook in the horizontal direction (c_{h k}), can be defined as follows:

Here, O₁ represents an oversampling ratio for the vertical direction and 0₂ represents an oversampling ratio for the horizontal direction.

[0047] In one example, this DFT codebook structure can be independent of inter-subarray spacing d_{sg V} and d_{sg H}, and the DFT codebook structure can be applicable for any inter- panel spacing. In addition, when inter-panel spacing is larger, a beam width can become narrower, and a number of grating lobes, - can increase.

A

[0048] In one example, the DFT quantization can be defined as follows:

c_mn, such that

can represent a code word obtained by a Kronecker product of codewords of horizontal and vertical directions, c_hiTn∈ {c_{h k}, k = 1, ... , M_ry 0₂} can represent a code word for the horizontal direction, and c_{v n}∈ {c_{v k}, k = 1, ... , N_r/O₁) can represent code word for the vertical direction.

[0049] In one example, when cross-polarized antennas are considered, a precoding matrix

(W₁) can be given by : wherein represent quantized

channels for horizontal and vertical polarization. An overall beamforming matrix (W) can be equal to W = W₁W₂, wherein W₂ = [1 a]^T and a represents a co-phasing parameter. Here, W₂ can co-phase two beams for a rank-1 transmission (for beam forming), or W₂ can be a matrix transformation for a rank-2 transmission (for a spatial multiplexing configuration).

[0050] In one configuration, if each panel has multiple RF chains, the DFT codebook can be updated since spacing between RF chains can be different (as shown in FIG. 3). Due to the spacing between RF chains being different, d_{sg V}≠ d_{s V} and/or d_{sg H}≠ d_{s H}. If a number of RF chains in the horizontal direction is represented by M_ry and a number of

RF chains in the vertical direction is represented by N_rf , then there can be RF

chains per panel.

[0051] Accordingly, the DFT codebook can be updated as follows:

T

k = 1, ... , M_rf0₂, wherein is one vector with a siz Here, v„ _fc can represent a

k'th codeword for the vertical direction, and v_{h k} can represent a k'th codeword for the horizontal direction.

[0052] In one example, the UE may not previously possess information about inter- antenna element and panel spacing. Rather, in the horizontal direction (v_{h k}), the UE can search for within a certain resolution (e.g., , and identify

s,H

an optimal S Here, S_h can represent an optimal inter-element and panel

spacing in a horizontal domain such that a throughput between the base station and the UE is maximized, or The UE can feedback only an index

^ _y

k of v_{h k}, since the base station can already know its own panel and antenna element distances. Similarly, for the vertical direction (v_{v k}), the UE can determine an optimal

Here, S_v can represent an optimal inter-element and panel spacing in a

vertical domain.

[0053] In one example, the parameters M_rj, N_rj, M_g, N_g, 0₁, 0₂ can be configured for the UE via higher layer signaling from the network.

[0054] In one configuration, given the parameters M_rj, N_rj, M_g, N_g, 0₁, 0₂, S_V, and S_h, the UE can determine feedback indexes n and m. In addition, the DFT quantization can be defined as follows: = Q(g) = v_mn, such that In this

example, \_mn = v_{h m} v_{v n}. Here, v_mn can represent a code word obtained by the

Kronecker product of code words of the horizontal and vertical directions, v_hiTn∈ {^v _h,_k> k ⁼ 1' - ' M_rf0₂, } can represent a code word for the horizontal direction, and v_{v n}∈ {v_{v k}, k = 1, ... , N_r/Oi, } can represent a code word for the vertical direction.

[0055] Moreover, the following equations can be defined:

In one example, if inter panel and antenna element distances are the same S₁ = S₂ = 0, wherein S-y and S₂ represent a phase correction parameter for the vertical and horizontal directions, respectively, or if d_{sg H} = 0.6λ, d_{s H} = 0.5λ, then S₂ =0.2.

[0056] FIG. 4 illustrates an example of a performance comparison for a novel discrete Fourier transform (DFT) codebook. In this example, M_g = 4, N_g = 2, 0_! = 8, 0₂ = 8, M = 4, N = 2, A_v = 2, A_h = 2, S_v = 20 and S_h = 20. In this example, a user equipment (UE) can have a 2 x 4 analog beamforming array, and a double directional geometric channel can be utilized with L=10 paths with Gaussian distributed path gain. As shown in FIG. 4, an ideal feedback is compared to the novel DFT codebook and an existing DFT codebook. The novel DFT codebook can have significant gain when considering an array antenna with different inter panel and antenna element spacing.

[0057] In one configuration, a two-stage DFT based quantization scheme can be defined for multi sectors at the base station. Here, a DFT codebook structure and feedback schemes can be defined when there is a channel between S_N sectors at the base station and the UE.

[0058] FIG. 5 illustrates an example of an antenna array for a two-sector base station. The base station can include a first sector and a second sector. The first sector can include a first antenna subarray structure and the second sector can include a second antenna subarray structure. In a given sector (e.g., the first sector or the second sector), a distance between antenna subarrays on a given panel in a vertical direction can be represented by d_{s V}, wherein d_{s V} = A_vd_v. A distance between antenna subarrays on a given panel in a horizontal direction can be represented by d_{s ,H}, wherein d_{s ,H} = A_Hd_H. A distance between adjacent antenna subarrays between two panels in the vertical direction can be represented by d_{sg V}, wherein d_{sg V} = d_{g V}— (M— A_v)d_v. A distance between adjacent antenna subarrays between two panels in the horizontal direction can be represented by d_Sg,H, wherein d_sgiH = d_giH— (N— A_H)d_H. [0059] In one example, assuming that each sector has the same antenna array structure, a same codebook can be utilized for each sector. A channel between sector s_t and a k* UE can be denoted by g_s¾, i = 1, ... , S_N, wherein S_N represents a total number of sectors. Then, a quantized precoding matrix (g) can be defined according to

can represent coefficients which

minimize a least square error minimizing with channel and beamforming vector, and

can represent a quantized channel for sector i.

[0060] In one example, an optimal coefficient vector (a) can be determined by solving the following least square problem:

Then, the solution

is the following:

[0061] In one example, the UE can feedback the coefficient vector a. In addition, the vector a can be quantized with a selected resolution to limit a feedback size.

[0062] In one configuration, several feedback schemes can be defined for when there is a single sector at the base station. These feedback schemes can be with respect to autocorrelation matrix based quantization, phase correction in the analog domain, and DFT feedback for multi-beam transmission.

[0063] In one example, with respect to auto-correlation matrix based quantization, a novel quantization technique can be defined to reduce an effect of quantization noise, which enables a reduction in feedback size. This quantization technique can be extended to a single user case.

[0064] In one example, an autocorrelation matrix of a channel for a given codebook (v_mn) can be defined. In this example, R_mn = E {gg^H}, wherein g∈ {g|Q(g) = V_mn}, . Here, R_mn can represent an autocorrelation matrix of the channel for a given code word v_mn. A SNR maximizing scheme (SNR_mn) can be considered in accordance with the following: SNR_mn = : Then, a SNR maximizing beamforming

vector can be a principal Eigen- vector of R_mn. In other words, w can be an Eigen vector of (Rmn). As a result, the auto-correlation matrix based quantization can be defined in accordance with the following: such that m, n =

This autocorrelation matrix based quantization can be applicable to

any type of codebook structure.

[0065] FIG. 6 illustrates an example of a performance comparison for a novel discrete Fourier transform (DFT) codebook and an auto-correlation matrix based feedback scheme. In this example, M_g = 4, N_g = 2, M = 4, N = 2, A_v = 2, A_h = 2, S_v = 8, and S_h = 8. In this example, a user equipment (UE) can have a 2 x 4 analog beamforming array, and a double directional geometric channel can be utilized with L=l paths with Gaussian distributed path gain. As shown in FIG. 6, an ideal feedback is compared to an autocorrelation based on 0₁ = 0₂ = 1, a novel DFT codebook based on 0₁ = 0₂ = 1, and a novel DFT codebook based on 0₁ = 0₂ = 2. The autocorrelation matrix based feedback scheme can utilize a reduced codebook size as compared to the DFT codebooks for similar performance.

[0066] In one example, with respect to phase correction in the analog domain, phase values of phase shifters can be adjusted according to an array structure of the base station. In other words, analog beamforming arrays can use the analog beamforming codebook by adjusting its phase values.

[0067] In one example, the phase values of the phase shifters can be:

wherein A_c represents a combined code word (analog beamforming vector) obtained by a Kronecker product of A_h and A_v, A_h represents an analog beamforming vector in the horizontal direction, and A_v represents an analog beamforming vector in the vertical direction.

[0068] Moreover, the following equations can be defined:

wherein l_w represents a column vector of size N with elements 1, and 1_M represents a column vector of size M with elements 1.

[0069] In one example, depending on the channel, no feedback can be utilized, as follows:

[0070] In one example, a vector size can be M_rfN_rf x 1. Alternatively, in general, the previous feedback schemes can be utilized.

[0071] FIG. 7 illustrates an example of a performance comparison for a novel discrete Fourier transform (DFT) codebook and no feedback scheme. In this example, O-y = 1, 0₂ = 1, M_g = 4, N_g = 2, M = 4, N = 2, A_v = 2, A_h = 2, S_v = 6, and S_h = 6. In this example, a user equipment (UE) can have a 2 x 4 analog beamforming array, and a double directional geometric channel can be utilized with L=10 paths with Gaussian distributed path gain. As shown in FIG. 7, an ideal feedback is compared to no feedback, a novel DFT codebook based on O = 1, and a novel DFT codebook based on O = 8. When phase compensation is performed at the phase shifters, the feedback size can be reduced and even no feedback can achieve favorable performance.

[0072] FIG. 8 illustrates an example of a multi-beam transmission from a base station. With respect to DFT feedback for multi-beam transmission, the base station can transmit data to a user equipment (UE) using multiple beams. A number of beams that are used to transmit the data can be denoted as B.

[0073] In one example, an indicator matrix A_{ind i} of size N_rf x M_rf can be defined, which can indicate RF chain indexes of beam i. In one example, the indicator matrix A_{ind i} can be defined in accordance with the following:

[0074] In one example, a diagonal matrix D_t can be defined as follows: ϋ_έ =

diag(vec(A_{ind i})), i = 1, ... , B. Then, a quantization can be defined in accordance with the following wherein α_έ represents coefficients which

minimize the least square error minimizing with channel and beamforming vector and ^V(V\ = Di^vmn such that m, n =

Here, the a_is can be determined v ' m,n

based on the following:

[0075] In one example, for the above quantization scheme, α_έ can be quantized for a limited feedback case. In addition, for each group of RF chains, phases and amplitudes can be quantized separately as follows: | | and

phase(a_{q i}) = Q_bp(phase(a_{q i})), i = 1, ... , β, wherein Q (-) is a quantizer with b_a and &p-bits resolution. In a special case, no amplitude and phase information feedback can be achieved by setting the quantization bits to b_a and bp-bits to zero.

[0076] FIG. 9 illustrates an example of a performance comparison for discrete Fourier transform (DFT) based feedback for multi-beam transmission. More specifically, the performance comparison can be for a rectangular panel array with multi-beam transmission. In this example, M_g = 4, N_g = 2, 0₁ = 4, 0₂ = 4, M = 4, N = 2, A_v = 2, A_h = 2, S_v = 3, and S_h = 3. In this example, a double directional geometric channel can be utilized with L=10 paths with Gaussian distributed path gain. As shown in FIG. 9, an ideal feedback is compared to a multi-beam DFT feedback and a single beam DFT feedback. The multi-beam DFT feedback can have an increased gain as compared to the single beam DFT feedback.

[0077] In one configuration, DFT codebook design with rectangular panel arrays and feedback schemes can be defined. The UE can determine the following parameters: M_rj, N_rf, Mg, N_g, 0₁, 0₂, S_V, and S_h. The UE can determine an optimal S_v and S_h. The UE can update the DFT codebook in accordance with the following:

Furthermore, the UE can select an appropriate feedback scheme. The feedback scheme can be for an updated DFT codebook based on a single sector base station. The feedback scheme can be for an updated DFT codebook based on a multiple sector base station. The feedback scheme can be based on an autocorrelation matrix, which can utilize an existing DFT codebook or a novel DFT codebook. The feedback scheme can be based on a phase correction in an analog domain, in which there is no feedback. Alternatively, the phase correction in the analog domain can be based on DFT or the autocorrelation matrix. In addition, the UE can utilize DFT feedback for a multi-beam transmission.

[0078] In one configuration, a two-stage DFT based codebook design can be defined for a rectangular panel array with different inter-panel and inter-antenna element distances. A first stage can consider a DFT codebook configured for equally spaced RF chains. A second stage can consider co-phasing of the RF chains by accounting for different inter- panel and inter-antenna element distances. For the first stage, parameters of the DFT codebook can be configured by higher layer signaling. For the second stage, parameters of the DFT codebook can be configured by the base station and/or estimated at the UE.

[0079] In one example, the two-stage DFT based codebook and co-phasing technique can be defined for sectors at the base station. With respect to an autocorrelation matrix based feedback scheme, the DFT codebook can include the two-stage DFT based codebook. With respect to a co-phasing scheme in the analog domain, a codebook and feedback scheme can be utilized for the digital domain to increase performance. In addition, a feedback scheme for multi-beam transmission at the base station can be defined.

[0080] Another example provides functionality 1000 of a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks, as shown in FIG. 10. The UE can comprise one or more processors. The one or more processors can be configured to decode a channel state information reference signal (CSI-RS) received from a base station, as in block 1010. The one or more processors can be configured to estimate a channel vector between the UE and the base station based on the CSI-RS, as in block 1020. The one or more processors can be configured to select a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna, as in block 1030. The one or more processors can be configured to encode feedback that includes the codebook index for transmission to the base station, as in block 1030. In addition, the UE can comprise memory configured to store the DFT codebook and the codebook index selected from the DFT codebook.

[0081] Another example provides functionality 1100 of a base station operable to process codebook indexes in discrete Fourier transform (DFT) codebooks received from a user equipment (UE), as shown in FIG. 11. The base station can comprise one or more processors. The one or more processors can be configured to encode a channel state information reference signal (CSI-RS) for transmission to the UE, wherein the CSI-RS enables an estimation of a channel vector between the base station and the UE, as in block 1110. The one or more processors can be configured to decode feedback received from the UE, wherein the feedback includes a codebook index selected from a DFT codebook, and the DFT codebook is based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna, as in block 1120. In addition, the base station can comprise memory configured to store the feedback that includes the codebook index received from the UE.

[0082] Another example provides at least one machine readable storage medium having instructions 1200 embodied thereon for selecting codebook indexes from discrete Fourier transform (DFT) codebooks, as shown in FIG. 12. The instructions can be executed on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The instructions when executed perform: decoding a channel state information reference signal (CSI-RS) received from a base station, as in block 1210. The instructions when executed perform: estimating a channel vector between the UE and the base station based on the CSI-RS, as in block 1220. The instructions when executed perform: selecting a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter- element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna, as in block 1230. The instructions when executed perform: encoding feedback that includes the codebook index for transmission to the base station, as in block 1240.

[0083] FIG. 13 illustrates an architecture of a system 1300 of a network in accordance with some embodiments. The system 1300 is shown to include a user equipment (UE) 1301 and a UE 1302. The UEs 1301 and 1302 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface.

[0084] In some embodiments, any of the UEs 1301 and 1302 can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), Proximity-Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived connections. The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network.

[0085] The UEs 1301 and 1302 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN) 1310— the RAN 1310 may be, for example, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN), aNextGen RAN (NG RAN), or some other type of RAN. The UEs 1301 and 1302 utilize connections 1303 and 1304, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections 1303 and 1304 are illustrated as an air interface to enable communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code- division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation (5G) protocol, a New Radio (NR) protocol, and the like.

[0086] In this embodiment, the UEs 1301 and 1302 may further directly exchange communication data via a ProSe interface 1305. The ProSe interface 1305 may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).

[0087] The UE 1302 is shown to be configured to access an access point (AP) 1306 via connection 1307. The connection 1307 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.15 protocol, wherein the AP 1306 would comprise a wireless fidelity (WiFi®) router. In this example, the AP 1306 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).

[0088] The RAN 1310 can include one or more access nodes that enable the connections 1303 and 1304. These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The RAN 1310 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 1311, and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node 1312.

[0089] Any of the RAN nodes 1311 and 1312 can terminate the air interface protocol and can be the first point of contact for the UEs 1301 and 1302. In some embodiments, any of the RAN nodes 1311 and 1312 can fulfill various logical functions for the RAN 1310 including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.

[0090] In accordance with some embodiments, the UEs 1301 and 1302 can be configured to communicate using Orthogonal Frequency -Division Multiplexing (OFDM) communication signals with each other or with any of the RAN nodes 1311 and 1312 over a multicarrier communication channel in accordance various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers.

[0091] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 1311 and 1312 to the UEs 1301 and 1302, while uplink transmissions can utilize similar techniques. The grid can be a time- frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time-frequency plane

representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time- frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated. There are several different physical downlink channels that are conveyed using such resource blocks.

[0092] The physical downlink shared channel (PDSCH) may carry user data and higher- layer signaling to the UEs 1301 and 1302. The physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs 1301 and 1302 about the transport format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) information related to the uplink shared channel. Typically, downlink scheduling (assigning control and shared channel resource blocks to the UE 1302 within a cell) may be performed at any of the RAN nodes 1311 and 1312 based on channel quality information fed back from any of the UEs 1301 and 1302. The downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs 1301 and 1302.

[0093] The PDCCH may use control channel elements (CCEs) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub-block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs). Four Quadrature Phase Shift Keying (QPSK) symbols may be mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DO) and the channel condition. There can be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L=l, 2, 4, or 8).

[0094] Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts. For example, some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission. The EPDCCH may be transmitted using one or more enhanced the control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations.

[0095] The RAN 1310 is shown to be communicatively coupled to a core network (CN) 1320— via an SI interface 1313. In embodiments, the CN 1320 may be an evolved packet core (EPC) network, a NextGen Packet Core (NPC) network, or some other type of CN. In this embodiment the SI interface 1313 is split into two parts: the SI -U interface 1314, which carries traffic data between the RAN nodes 1311 and 1312 and the serving gateway (S-GW) 1322, and the Sl-mobility management entity (MME) interface 1315, which is a signaling interface between the RAN nodes 1311 and 1312 and MMEs 1321.

[0096] In this embodiment, the CN 1320 comprises the MMEs 1321, the S-GW 1322, the Packet Data Network (PDN) Gateway (P-GW) 1323, and a home subscriber server (HSS) 1324. The MMEs 1321 may be similar in function to the control plane of legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN). The MMEs 1321 may manage mobility aspects in access such as gateway selection and tracking area list management. The HSS 1324 may comprise a database for network users, including subscription-related information to support the network entities' handling of

communication sessions. The CN 1320 may comprise one or several HSSs 1324, depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc. For example, the HSS 1324 can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc.

[0097] The S-GW 1322 may terminate the SI interface 1313 towards the RAN 1310, and routes data packets between the RAN 1310 and the CN 1320. In addition, the S-GW 1322 may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement.

[0098] The P-GW 1323 may terminate an SGi interface toward a PDN. The P-GW 1323 may route data packets between the EPC network 1323 and external networks such as a network including the application server 1330 (alternatively referred to as application function (AF)) via an Internet Protocol (IP) interface 1325. Generally, the application server 1330 may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). In this embodiment, the P-GW 1323 is shown to be communicatively coupled to an application server 1330 via an IP communications interface 1325. The application server 1330 can also be configured to support one or more communication services (e.g., Voice- over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs 1301 and 1302 via the CN 1320. [0099] The P-GW 1323 may further be a node for policy enforcement and charging data collection. Policy and Charging Enforcement Function (PCRF) 1326 is the policy and charging control element of the CN 1320. In a non-roaming scenario, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE's Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with local breakout of traffic, there may be two PCRFs associated with a UE's IP-CAN session: a Home PCRF (H-PCRF) within a HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF 1326 may be communicatively coupled to the application server 1330 via the P-GW 1323. The application server 1330 may signal the PCRF 1326 to indicate a new service flow and select the appropriate Quality of Service (QoS) and charging parameters. The PCRF 1326 may provision this rule into a Policy and Charging Enforcement Function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server 1330.

[00100] FIG. 14 illustrates example components of a device 1400 in accordance with some embodiments. In some embodiments, the device 1400 may include application circuitry 1402, baseband circuitry 1404, Radio Frequency (RF) circuitry 1406, front-end module (FEM) circuitry 1408, one or more antennas 1410, and power management circuitry (PMC) 1412 coupled together at least as shown. The components of the illustrated device 1400 may be included in a UE or a RAN node. In some embodiments, the device 1400 may include less elements (e.g., a RAN node may not utilize application circuitry 1402, and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device 1400 may include additional elements such as, for example, memory /storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C-RAN) implementations).

[00101] The application circuitry 1402 may include one or more application processors. For example, the application circuitry 1402 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with or may include memory /storage and may be configured to execute instructions stored in the memory /storage to enable various applications or operating systems to run on the device 1400. In some embodiments, processors of application circuitry 1402 may process IP data packets received from an EPC.

[00102] The baseband circuitry 1404 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 1404 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 1406 and to generate baseband signals for a transmit signal path of the RF circuitry 1406. Baseband processing circuity 1404 may interface with the application circuitry 1402 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 1406. For example, in some embodiments, the baseband circuitry 1404 may include a third generation (3G) baseband processor 1404a, a fourth generation (4G) baseband processor 1404b, a fifth generation (5G) baseband processor 1404c, or other baseband processors) 1404d for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 1404 (e.g., one or more of baseband processors 1404a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 1406. In other embodiments, some or all of the functionality of baseband processors 1404a-d may be included in modules stored in the memory 1404g and executed via a Central Processing Unit (CPU) 1404e. The radio control functions may include, but are not limited to, signal modulation demodulation, encoding/decoding, radio frequency shifting, etc. In some embodiments,

modulation demodulation circuitry of the baseband circuitry 1404 may include Fast- Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 1404 may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation demodulation and encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.

[00103] In some embodiments, the baseband circuitry 1404 may include one or more audio digital signal processor(s) (DSP) 1404f. The audio DSP(s) 1404f may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 1404 and the application circuitry 1402 may be implemented together such as, for example, on a system on a chip (SOC).

[00104] In some embodiments, the baseband circuitry 1404 may provide for

communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 1404 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 1404 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[00105] RF circuitry 1406 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 1406 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 1406 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 1408 and provide baseband signals to the baseband circuitry 1404. RF circuitry 1406 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 1404 and provide RF output signals to the FEM circuitry 1408 for transmission.

[00106] In some embodiments, the receive signal path of the RF circuitry 1406 may include mixer circuitry 1406a, amplifier circuitry 1406b and filter circuitry 1406c. In some embodiments, the transmit signal path of the RF circuitry 1406 may include filter circuitry 1406c and mixer circuitry 1406a RF circuitry 1406 may also include synthesizer circuitry 1406d for synthesizing a frequency for use by the mixer circuitry 1406a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 1406a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 1408 based on the synthesized frequency provided by synthesizer circuitry 1406d. The amplifier circuitry 1406b may be configured to amplify the down-converted signals and the filter circuitry 1406c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 1404 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 1406a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.

[00107] In some embodiments, the mixer circuitry 1406a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 1406d to generate RF output signals for the FEM circuitry 1408. The baseband signals may be provided by the baseband circuitry 1404 and may be filtered by filter circuitry 1406c.

[00108] In some embodiments, the mixer circuitry 1406a of the receive signal path and the mixer circuitry 1406a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry 1406a of the receive signal path and the mixer circuitry 1406a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 1406a of the receive signal path and the mixer circuitry 1406a may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry 1406a of the receive signal path and the mixer circuitry 1406a of the transmit signal path may be configured for super-heterodyne operation.

[00109] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 1406 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 1404 may include a digital baseband interface to communicate with the RF circuitry 1406.

[00110] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[00111] In some embodiments, the synthesizer circuitry 1406d may be a fractional-N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 1406d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.

[00112] The synthesizer circuitry 1406d may be configured to synthesize an output frequency for use by the mixer circuitry 1406a of the RF circuitry 1406 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 1406d may be a fractional N/N+l synthesizer.

[00113] In some embodiments, frequency input may be provided by a voltage controlled oscillator (V CO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 1404 or the applications processor 1402 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor 1402.

[00114] Synthesizer circuitry 1406d of the RF circuitry 1406 may include a divider, a delay -locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle. [00115] In some embodiments, synthesizer circuitry 1406d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 1406 may include an IQ/polar converter.

[00116] FEM circuitry 1408 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 1410, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 1406 for further processing. FEM circuitry 1408 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 1406 for transmission by one or more of the one or more antennas 1410. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 1406, solely in the FEM 1408, or in both the RF circuitry 1406 and the FEM 1408.

[00117] In some embodiments, the FEM circuitry 1408 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 1406). The transmit signal path of the FEM circuitry 1408 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 1406), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 1410).

[00118] In some embodiments, the PMC 1412 may manage power provided to the baseband circuitry 1404. In particular, the PMC 1412 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC 1412 may often be included when the device 1400 is capable of being powered by a battery, for example, when the device is included in a UE. The PMC 1412 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation

characteristics.

[00119] While FIG. 14 shows the PMC 1412 coupled only with the baseband circuitry 1404. However, in other embodiments, the PMC 14 12 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 1402, RF circuitry 1406, or FEM 1408.

[00120] In some embodiments, the PMC 1412 may control, or otherwise be part of, various power saving mechanisms of the device 1400. For example, if the device 1400 is in an RRC Connected state, where it is still connected to the RAN node as it expects to receive traffic shortly, then it may enter a state known as Discontinuous Reception Mode (DRX) after a period of inactivity. During this state, the device 1400 may power down for brief intervals of time and thus save power.

[00121] If there is no data traffic activity for an extended period of time, then the device 1400 may transition off to an RRC Idle state, where it disconnects from the network and does not perform operations such as channel quality feedback, handover, etc. The device 1400 goes into a very low power state and it performs paging where again it periodically wakes up to listen to the network and then powers down again. The device 1400 may not receive data in this state, in order to receive data, it must transition back to

RRC_Connected state.

[00122] An additional power saving mode may allow a device to be unavailable to the network for periods longer than a paging interval (ranging from seconds to a few hours). During this time, the device is totally unreachable to the network and may power down completely. Any data sent during this time incurs a large delay and it is assumed the delay is acceptable.

[00123] Processors of the application circuitry 1402 and processors of the baseband circuitry 1404 may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry 1404, alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 1404 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below.

[00124] FIG. 15 illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry 1404 of FIG. 14 may comprise processors 1404a-1404e and a memory 1404g utilized by said processors. Each of the processors 1404a-1404e may include a memory interface, 1504a-1504e, respectively, to send/receive data to/from the memory 1404g.

[00125] The baseband circuitry 1404 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 1512 (e.g., an interface to send/receive data to/from memory external to the baseband circuitry 1404), an application circuitry interface 1514 (e.g., an interface to send/receive data to/from the application circuitry 1402 of FIG. 14), an RF circuitry interface 1516 (e.g., an interface to send/receive data to/from RF circuitry 1406 of FIG. 14), a wireless hardware connectivity interface 1518 (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface 1520 (e.g., an interface to send/receive power or control signals to/from the PMC 1412.

[00126] FIG. 16 provides an example illustration of the wireless device, such as a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile

communication device, a tablet, a handset, or other type of wireless device. The wireless device can include one or more antennas configured to communicate with a node, macro node, low power node (LPN), or, transmission station, such as a base station (BS), an evolved Node B (eNB), a baseband processing unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station (RS), a radio equipment (RE), or other type of wireless wide area network (WWAN) access point. The wireless device can be configured to communicate using at least one wireless communication standard such as, but not limited to, 3 GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi. The wireless device can communicate using separate antennas for each wireless communication standard or shared antennas for multiple wireless communication standards. The wireless device can communicate in a wireless local area network

(WLAN), a wireless personal area network (WPAN), and/or a WWAN. The wireless device can also comprise a wireless modem. The wireless modem can comprise, for example, a wireless radio transceiver and baseband circuitry (e.g., a baseband processor). The wireless modem can, in one example, modulate signals that the wireless device transmits via the one or more antennas and demodulate signals that the wireless device receives via the one or more antennas.

[00127] FIG. 16 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen can be a liquid crystal display (LCD) screen, or other type of display screen such as an organic light emitting diode (OLED) display. The display screen can be configured as a touch screen. The touch screen can use capacitive, resistive, or another type of touch screen technology. An application processor and a graphics processor can be coupled to internal memory to provide processing and display capabilities. A non-volatile memory port can also be used to provide data input output options to a user. The non-volatile memory port can also be used to expand the memory capabilities of the wireless device. A keyboard can be integrated with the wireless device or wirelessly connected to the wireless device to provide additional user input. A virtual keyboard can also be provided using the touch screen.

Examples

[00128] The following examples pertain to specific technology embodiments and point out specific features, elements, or actions that can be used or otherwise combined in achieving such embodiments.

[00129] Example 1 includes an apparatus of a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks, the apparatus comprising: one or more processors configured to: decode a channel state information reference signal (CSI-RS) received from a base station; estimate a channel vector between the UE and the base station based on the CSI-RS; select a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter- element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and encode feedback that includes the codebook index for transmission to the base station; and a memory interface configured to send to a memory the DFT codebook and the codebook index selected from the DFT codebook.

[00130] Example 2 includes the apparatus of Example 1, further comprising a transceiver configured to: receive the CSI-RS from the base station; and transmit, to the base station, the feedback that includes the codebook index in a narrowband transmission or a wideband transmission.

[00131] Example 3 includes the apparatus of any of claims 1 to 2, wherein the one or more processors are further configured to: configure the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g ,H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_sg,H represents an inter-subarray spacing in a horizontal domain, and d_g,H represents an inter-panel distance in the horizontal domain.

[00132] Example 4 includes the apparatus of any of claims 1 to 2, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: c_{v k} = wherein N_g represents a number of

panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by: c_{h k} = wherein M_g represents a number

of panels in a column of the uniform rectangular antenna panel array, M_rj represents a number of RF chains in a horizontal domain at the base station, 0₂ represents a second oversampling ratio, k represents a codebook index, and T represents a Transpose function.

[00133] Example 5 includes the apparatus of any of claims 1 to 4, wherein the number of RF chains in the horizontal domain (M_rj), the number of RF chains in the vertical domain (N_rf ), the number of panels in the column of the uniform rectangular antenna panel array (Mg), the number of panels in the row of the uniform rectangular antenna panel array (N_g), the first oversampling ratio (O-J, and the second oversampling ratio (0₂) are received from the base station via higher layer signaling.

[00134] Example 6 includes the apparatus of any of claims 1 to 5, wherein the one or more processors are further configured to: identify an optimal inter-element and panel spacing in a vertical domain (S_v) for the uniform rectangular antenna panel array, wherein S_v is represented by and identify an optimal inter-element and panel spacing in

a horizontal domain (S_h) for the uniform rectangular antenna panel array, wherein S_h is represented by wherein d_{sg V} represents an inter-subarray spacing in a

vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, d_{s V} represents a distance between antenna subarrays on a given panel in a vertical domain, and d_{s H} represents a distance between antenna subarrays on a given panel in a horizontal domain.

[00135] Example 7 includes the apparatus of any of claims 1 to 6, wherein the one or more processors are further configured to: configure the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_{s V} and d_{sg H}≠ d_{s H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_sg,H represents an inter-subarray spacing in a horizontal domain, and d_g,H represents an inter-panel distance in the horizontal domain.

[00136] Example 8 includes the apparatus of any of claims 1 to 7, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: c_{v k} = wherein N_rf represents a

number of RF chains in a vertical domain at the base station, 0₁ represents an

oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_hik) is represented by: c_{h k} = wherein M_rj represents a

number of RF chains in a horizontal domain at the base station, 0₂ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function.

[00137] Example 9 includes the apparatus of any of claims 1 to 8, wherein the one or more processors are further configured to: configure the DFT codebook based on whether the uniform rectangular antenna panel array includes a single sector or multiple sectors.

[00138] Example 10 includes the apparatus of any of claims 1 to 9, wherein the one or more processors are further configured to: apply an auto-correlation matrix based quantization to the feedback to reduce a quantization noise and a feedback size, and the auto-correlation matrix based quantization is utilized when the DFT codebook is configured based on inter-element distances and inter-panel distances in the uniform rectangular antenna panel array of the base station antenna.

[00139] Example 11 includes the apparatus of any of claims 1 to 10, wherein the one or more processors are further configured to: encode the feedback that includes the codebook index for transmission to the base station in response to receiving a multi-beam transmission from the base station.

[00140] Example 12 includes an apparatus of a base station operable to process codebook indexes in discrete Fourier transform (DFT) codebooks received from a user equipment (UE), the apparatus comprising: one or more processors configured to: encode a channel state information reference signal (CSI-RS) for transmission to the UE, wherein the CSI- RS enables an estimation of a channel vector between the base station and the UE; and decode feedback received from the UE, wherein the feedback includes a codebook index selected from a DFT codebook, and the DFT codebook is based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and a memory interface configured to send to a memory the feedback that includes the codebook index received from the UE.

[00141] Example 13 includes the apparatus of Example 12, wherein the DFT codebook includes a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_sg,H represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain.

[00142] Example 14 includes the apparatus of any of Examples 12 to 13, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: c_{v k} = wherein N_g represents a number of

panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents _, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by: c_{h k} = wherein M_g represents a number

of panels in a column of the uniform rectangular antenna panel array, M_ry represents a number of RF chains in a horizontal domain at the base station, 0₂ represents a second oversampling ratio, k represents a codebook index, and T represents a Transpose function.

[00143] Example 15 includes the apparatus of any of Examples 12 to 14, wherein the number of RF chains in the horizontal domain (M_rj), the number of RF chains in the vertical domain (N_ry), the number of panels in the column of the uniform rectangular antenna panel array (M_g), the number of panels in the row of the uniform rectangular antenna panel array (N_g), the first oversampling ratio (O-J, and the second oversampling ratio (0₂ ) are configured for the UE via higher layer signaling. [00144] Example 16 includes the apparatus of any of Examples 12 to 15, wherein the DFT codebook includes a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_{s V} and d_{sg H}≠ d_{s H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter- panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_gJi represents an inter-panel distance in the horizontal domain.

[00145] Example 17 includes the apparatus of any of Examples 12 to 16, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: c_{v k} = wherein N_rf represents a

number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by: c_{h k} = wherein M_ry represents a

[00146] Example 18 includes at least one machine readable storage medium having instructions embodied thereon for selecting codebook indexes from discrete Fourier transform (DFT) codebooks, the instructions when executed by one or more processors of the UE perform the following: decoding a channel state information reference signal (CSI-RS) received from a base station; estimating a channel vector between the UE and the base station based on the CSI-RS; selecting a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and encoding feedback that includes the codebook index for transmission to the base station.

[00147] Example 19 includes the at least one machine readable storage medium of Example 18, further comprising instructions when executed perform the following:

configuring the DFT codebook to include a DFT codebook in a vertical domain (c_v,k) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_Sg,H = dg,H, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_gy represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter- subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: wherein N_g

represents a number of panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by: c_{h k} =

T

wherein M_g represents a number

[00148] Example 20 includes the at least one machine readable storage medium of any of Examples 18 to 19, further comprising instructions when executed perform the following: identifying an optimal inter-element and panel spacing in a vertical domain (S_v) for the uniform rectangular antenna panel array, wherein S_v is represented by and

identifying an optimal inter-element and panel spacing in a horizontal domain (S_h) for the uniform rectangular antenna panel array, wherein S_h is represented by

wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, d_sy represents a distance between antenna subarrays on a given panel in a vertical domain, and d_{s H} represents a distance between antenna subarrays on a given panel in a horizontal domain.

[00149] Example 21 includes the at least one machine readable storage medium of any of Examples 18 to 20, further comprising instructions when executed perform the following: configuring the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_hik) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_{s V} and d_{sg H}≠ d_{s H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_gy represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter- subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by:

wherein N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by: c wherein M_rj

represents a number of RF chains in a horizontal domain at the base station, 0₂ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function.

[00150] Example 22 includes the at least one machine readable storage medium of any of Examples 18 to 21, further comprising instructions when executed perform the following: configuring the DFT codebook based on whether the uniform rectangular antenna panel array includes a single sector or multiple sectors.

[00151] Example 23 includes the at least one machine readable storage medium of any of Examples 18 to 22, further comprising instructions when executed perform the following: applying an auto-correlation matrix based quantization to the feedback to reduce a quantization noise and a feedback size, and the auto-correlation matrix based quantization is utilized when the DFT codebook is configured based on inter-element distances and inter-panel distances in the uniform rectangular antenna panel array of the base station antenna.

[00152] Example 24 includes the at least one machine readable storage medium of any of Examples 18 to 23, further comprising instructions when executed perform the following: encoding the feedback that includes the codebook index for transmission to the base station in response to receiving a multi-beam transmission from the base station.

[00153] Example 25 includes a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks, the UE comprising: means for decoding a channel state information reference signal (CSI-RS) received from a base station; means for estimating a channel vector between the UE and the base station based on the CSI-RS; means for selecting a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and means for encoding feedback that includes the codebook index for transmission to the base station.

[00154] Example 26 includes the UE of Example 25, further comprising: means for configuring the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_hik) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_gy represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter- subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by:

represents a number of panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_hik) is represented by: c_{h k} = wherein M_g represents a number

[00155] Example 27 includes the UE of any of Examples 25 to 26, further comprising: means for identifying an optimal inter-element and panel spacing in a vertical domain (S_v) for the uniform rectangular antenna panel array, wherein S_v is represented by S_v = m^ _means f_or identifying an optimal inter-element and panel spacing in a

horizontal domain (S_h) for the uniform rectangular antenna panel array, wherein S_h is represented by wherein d_{sa v} represents an inter-subarray spacing in a

vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, d_sy represents a distance between antenna subarrays on a given panel in a vertical domain, and d_{s H} represents a distance between antenna subarrays on a given panel in a horizontal domain.

[00156] Example 28 includes the UE of any of Examples 25 to 27, further comprising: means for configuring the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_{s V} and d_{sg H}≠ d_{s H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_gy represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter- subarray spacing in a horizontal domain, and d_g,H represents an inter-panel distance in the horizontal domain, wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by:

wherein N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by:

[00157] Example 29 includes the UE of any of Examples 25 to 28, further comprising: means for configuring the DFT codebook based on whether the uniform rectangular antenna panel array includes a single sector or multiple sectors.

[00158] Example 30 includes the UE of any of Examples 25 to 29, further comprising: means for applying an auto-correlation matrix based quantization to the feedback to reduce a quantization noise and a feedback size, and the auto-correlation matrix based quantization is utilized when the DFT codebook is configured based on inter-element distances and inter-panel distances in the uniform rectangular antenna panel array of the base station antenna.

[00159] Example 31 includes the UE of any of Examples 25 to 30, further comprising: means for encoding the feedback that includes the codebook index for transmission to the base station in response to receiving a multi-beam transmission from the base station.

[00160] Various techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, compact disc-read-only memory (CD-ROMs), hard drives, non-transitory computer readable storage medium, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques. In the case of program code execution on programmable computers, the computing device may include a processor, a storage medium readable by the processor (including volatile and nonvolatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and/or storage elements may be a random-access memory (RAM), erasable programmable read only memory (EPROM), flash drive, optical drive, magnetic hard drive, solid state drive, or other medium for storing electronic data. The node and wireless device may also include a transceiver module (i.e., transceiver), a counter module (i.e., counter), a processing module (i.e., processor), and/or a clock module (i.e., clock) or timer module (i.e., timer). In one example, selected components of the transceiver module can be located in a cloud radio access network (C-RAN). One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.

[00161] As used herein, the term "circuitry" may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, circuitry may include logic, at least partially operable in hardware.

[00162] It should be understood that many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very -large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

[00163] Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module may not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

[00164] Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. The modules may be passive or active, including agents operable to perform desired functions.

[00165] Reference throughout this specification to "an example" or "exemplary" means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present technology. Thus, appearances of the phrases "in an example" or the word "exemplary" in various places throughout this specification are not necessarily all referring to the same embodiment.

[00166] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present technology may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as defacto equivalents of one another, but are to be considered as separate and autonomous representations of the present technology.

[00167] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of layouts, distances, network examples, etc., to provide a thorough understanding of embodiments of the technology. One skilled in the relevant art will recognize, however, that the technology can be practiced without one or more of the specific details, or with other methods, components, layouts, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the technology.

[00168] While the forgoing examples are illustrative of the principles of the present technology in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the technology. Accordingly, it is not intended that the technology be limited, except as by the claims set forth below.

Claims

CLAIMS What is claimed is:

1. An apparatus of a user equipment (UE) operable to select codebook indexes from discrete Fourier transform (DFT) codebooks, the apparatus comprising: one or more processors configured to:

decode a channel state information reference signal (CSI-RS) received from a base station;

estimate a channel vector between the UE and the base station based on the CSI-RS;

select a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and

encode feedback that includes the codebook index for transmission to the base station; and

a memory interface configured to send to a memory the DFT codebook and the codebook index selected from the DFT codebook.

2. The apparatus of claim 1, further comprising a transceiver configured to:

receive the CSI-RS from the base station; and

transmit, to the base station, the feedback that includes the codebook index in a narrowband transmission or a wideband transmission.

3. The apparatus of claim 1, wherein the one or more processors are further configured to: configure the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_gy represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain.

4. The apparatus of claim 3, wherein:

the DFT codebook in the vertical domain (c_{v k}) is represented by:

wherein N_g represents a number of panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents a codebook index

, and T represents a Transpose function; and

the DFT codebook in the horizontal domain (c_{h k}) is represented by:

wherein M_g represents a number of panels in a column of the uniform rectangular antenna panel array, M_rj represents a number of RF chains in a horizontal domain at the base station, 0₂ represents a second oversampling ratio, k represents a codebook index, and T represents a Transpose function.

5. The apparatus of claim 4, wherein the number of RF chains in the horizontal domain (M_rf), the number of RF chains in the vertical domain (N_rf), the number of panels in the column of the uniform rectangular antenna panel array (M_g), the number of panels in the row of the uniform rectangular antenna panel array (N_g), the first oversampling ratio (O-J, and the second

oversampling ratio (0₂) are received from the base station via higher layer signaling.

6. The apparatus of any of claims 1 to 5, wherein the one or more processors are further configured to: identify an optimal inter-element and panel spacing in a vertical domain (S_v) for the uniform rectangular antenna panel array, wherein S_v is represented

identify an optimal inter-element and panel spacing in a horizontal domain (S_h) for the uniform rectangular antenna panel array, wherein S_h is represented

7. The apparatus of any of claims 1 to 5, wherein the one or more processors are further configured to: configure the DFT codebook to include a DFT codebook in a vertical domain (c_v,k) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_sy and dsg,H≠ ds,H, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_g,H represents an inter-panel distance in the horizontal domain.

8. The apparatus of claim 7, wherein:

the DFT codebook in the vertical domain (c_v,k) is represented by:

wherein N_rj represents a number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by:

wherein M_rj represents a number of RF chains in a horizontal domain at the base station, 0₂ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function. 9. The apparatus of claim 1, wherein the one or more processors are further configured to: configure the DFT codebook based on whether the uniform rectangular antenna panel array includes a single sector or multiple sectors. 10. The apparatus of claim 1, wherein the one or more processors are further configured to: apply an auto-correlation matrix based quantization to the feedback to reduce a quantization noise and a feedback size, and the autocorrelation matrix based quantization is utilized when the DFT codebook is configured based on inter-element distances and inter-panel distances in the uniform rectangular antenna panel array of the base station antenna 1 1. The apparatus of claim 1, wherein the one or more processors are further configured to: encode the feedback that includes the codebook index for transmission to the base station in response to receiving a multi-beam transmission from the base station.

12. An apparatus of a base station operable to process codebook indexes in discrete Fourier transform (DFT) codebooks received from a user equipment (UE), the apparatus comprising:

one or more processors configured to:

encode a channel state information reference signal (CSI-RS) for transmission to the UE, wherein the CSI-RS enables an estimation of a channel vector between the base station and the UE; and

decode feedback received from the UE, wherein the feedback includes a codebook index selected from a DFT codebook, and the DFT codebook is based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and

a memory interface configured to send to a memory the feedback that includes the codebook index received from the UE.

13. The apparatus of claim 12, wherein the DFT codebook includes a DFT

codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_hik) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain.

14. The apparatus of claim 13, wherein:

the DFT codebook in the vertical domain (c_v,k) is represented by:

wherein N_g represents a number of panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents a codebook index, and T represents a Transpose function; and the DFT codebook in the horizontal domain (c_{h k}) is represented by:

15. The apparatus of claim 14, wherein the number of RF chains in the horizontal domain (M_rf), the number of RF chains in the vertical domain (N_rf), the number of panels in the column of the uniform rectangular antenna panel array (Mg), the number of panels in the row of the uniform rectangular antenna panel array (N_g), the first oversampling ratio (O-J, and the second

oversampling ratio (0₂) are configured for the UE via higher layer signaling.

16. The apparatus of any of claims 12 to 15, wherein the DFT codebook includes a DFT codebook in a vertical domain (c_v,k) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_sy and d_{sg H}≠ d_s,H , wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain.

17. The apparatus of claim 16, wherein:

the DFT codebook in the vertical domain (c_{v k}) is represented by:

wherein N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and

the DFT codebook in the horizontal domain (c_{h k}) is represented by:

wherein M_rf represents a number of RF chains in a horizontal domain at the base station, 0₂ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function.

18. At least one machine readable storage medium having instructions embodied thereon for selecting codebook indexes from discrete Fourier transform (DFT) codebooks, the instructions when executed by one or more processors of the UE perform the following:

decoding a channel state information reference signal (CSI-RS) received from a base station;

estimating a channel vector between the UE and the base station based on the CSI-RS;

selecting a codebook index from a DFT codebook, wherein the DFT codebook is configured at the UE based on different inter-element distances and inter-panel distances in a uniform rectangular antenna panel array of a base station antenna; and

encoding feedback that includes the codebook index for transmission to the base station.

19. The at least one machine readable storage medium of claim 18, further

comprising instructions when executed perform the following:

configuring the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes a single radio frequency (RF) chain and distances between subarrays in antenna panel(s) are represented by d_{sg V} = d_{g V} and d_{sg H} = d_{g ,H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_{sg ,H} represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain,

wherein: the DFT codebook in the vertical domain (c_{v k}) is represented by: wherein N_g

represents a number of panels in a row of the uniform rectangular antenna panel array, N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents a first oversampling ratio, k represents _, and T represents a Transpose function; and

the DFT codebook in the horizontal domain (c_{h k}) is represented

wherein M₅ represents a number of panels in a column of the uniform rectangular antenna panel array, M_rj represents a number of RF chains in a horizontal domain at the base station, 0₂ represents a second oversampling ratio, k represents a codebook index, and T represents a Transpose function.

20. The at least one machine readable storage medium of claim 18, further

comprising instructions when executed perform the following:

identifying an optimal inter-element and panel spacing in a vertical domain (S_v) for the uniform rectangular antenna panel array, wherein S_v is represented

21. The at least one machine readable storage medium of any of claims 18 to 20, further comprising instructions when executed perform the following:

configuring the DFT codebook to include a DFT codebook in a vertical domain (c_{v k}) and a DFT codebook in a horizontal domain (c_{h k}) when each antenna panel in the uniform rectangular antenna panel array includes multiple radio frequency (RF) chains and distances between subarrays in antenna panel(s) are represented by d_{sg V}≠ d_{s V} and d_{sg H}≠ d_{s H}, wherein d_{sg V} represents an inter-subarray spacing in a vertical domain, d_{g V} represents an inter-panel distance in the vertical domain, d_{sg H} represents an inter-subarray spacing in a horizontal domain, and d_{g H} represents an inter-panel distance in the horizontal domain,

wherein:

the DFT codebook in the vertical domain (c_{v k}) is represented by: wherein

N_rf represents a number of RF chains in a vertical domain at the base station, 0₁ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function; and

the DFT codebook in the horizontal domain (c_{h k}) is represented by:

wherein M_rj represents a number of RF chains in a horizontal domain at the base station, 0₂ represents an oversampling ratio, k represents a codebook index, and T represents a Transpose function.

22. The at least one machine readable storage medium of any of claims 18 to 20, further comprising instructions when executed perform the following:

configuring the DFT codebook based on whether the uniform rectangular antenna panel array includes a single sector or multiple sectors.

23. The at least one machine readable storage medium of claim 18, further

comprising instructions when executed perform the following: applying an auto-correlation matrix based quantization to the feedback to reduce a quantization noise and a feedback size, and the auto-correlation matrix based quantization is utilized when the DFT codebook is configured based on inter- element distances and inter-panel distances in the uniform rectangular antenna panel array of the base station antenna 24. The at least one machine readable storage medium of claim 18, further

comprising instructions when executed perform the following: encoding the feedback that includes the codebook index for transmission to the base station in response to receiving a multi-beam transmission from the base station.