KR102425095B1 - Apparatus and method for performing beam forming operation in communication system supporting frequency division-multiple input multiple output scheme - Google Patents

Abstract

The present invention is a 5th generation (5th-Generation: 5G) or pre-5G to be provided to support higher data rates after a 4th-generation (4G) communication system such as Long Term Evolution (LTE) It relates to (pre-5G) communication systems. The present invention provides a method for performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, a schematic diagram of a first dominant beam ( rough) detecting the beam; detecting at least two codeword candidates based on the coarse beam of the first dominant beam; and selecting one of the at least two codeword candidates as a final codeword.

Description

Apparatus and method for performing beamforming operation in a communication system supporting frequency division-multiple input multiple output method

The present invention performs a beam forming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO, hereinafter referred to as "FD-MIMO") method. A beamforming operation based on a Kronecker-product mono codebook and a Kronecker product dual codebook, in particular, in a communication system supporting an FD-MIMO scheme. It relates to an apparatus and method for performing the

In order to meet the increasing demand for wireless data traffic after the commercialization of the 4th-generation (4th-generation: 4G, hereinafter referred to as “4G”) communication system, the improved 5th-generation (5th-generation: 5G, hereinafter “5G”) Efforts are being made to develop a communication system (hereinafter referred to as "pre-5G") or a pre-5G (hereinafter referred to as "pre-5G") communication system. For this reason, the 5G communication system or the pre-5G communication system is a 4G network after (beyond 4G network) communication system or long-term evolution (LTE, hereinafter referred to as "LTE") After the system (Post LTE) It is called the later system.

In order to achieve a high data rate, the 5G communication system is implemented in a millimeter wave (mmWave, hereinafter referred to as “mmWave”) band (eg, a frequency band such as a 60 gigabyte (60 GHz) band). are being considered In order to mitigate the path loss of radio waves in the ultra-high frequency band and increase the propagation distance of radio waves, in the 5G communication system, beam forming, massive multi-input multi-output (massive multi-input multi-output: massive MIMO, hereinafter " massive MIMO") method, full dimensional multiple input multiple output (ful dimensional MIMO: FD-MIMO, hereinafter referred to as "FD-MIMO") method, array antenna method, and analog A beam-forming (analog beam-forming) method and a large scale antenna method are being discussed.

In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud radio access network: cloud RAN), an ultra-dense network (ultra-dense network) , device to device (D2D, hereinafter referred to as “D2D”) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP) , and technologies such as interference cancellation are being developed.

In addition, in the 5G system, hybrid frequency shift keying (FSK, hereinafter referred to as "FSK"), which is an advanced coding modulation (ACM, hereinafter referred to as "ACM") method, and orthogonal Amplitude modulation (quadrature amplitude modulation: QAM, hereinafter referred to as "QAM") (hybrid FSK and QAM: FQAM, hereinafter referred to as "FQAM") scheme and sliding window superposition coding (SWSC, hereinafter) "SWSC") method, an advanced access technology filter bank multi carrier (FBMC, hereinafter referred to as "FBMC") method, and non-orthogonal multiple access: NOMA (hereinafter referred to as “NOMA”) method and a sparse code multiple access (SCMA, hereinafter referred to as “SCMA”) method are being developed. Various schemes have been proposed, and a representative scheme among them is a MIMO scheme using a plurality of antennas. In the MIMO scheme, in order to use signal processing techniques that enable high data rate transmission, the transmitter acquires accurate channel state information (CSI, hereinafter referred to as "CSI"). it is essential

Meanwhile, in cellular systems supporting a frequency division duplexing (FDD, hereinafter referred to as "FDD") scheme, CSI estimated by the receiver is transmitted to the transmitter through a feedback link.

In addition, in a massive MIMO (hereinafter, referred to as “massive MIMO”) having a plurality of antennas, a plurality of feedback bits are required to accurately quantize CSI.

Here, a normalized beamforming gain using a random vector quantization (RVQ, hereinafter referred to as “RVQ”) codebook may be expressed as Equation 1 below.

은 다중 입력 단일 출력(multiple input single output: MISO, 이하 "MISO"라 칭하기로 한다) 채널 벡터를 나타내고,

은 단위 놈(unit norm) 빔포밍 코드워드(beamforming codeword)를 나타내고, 는 RVQ 코드북에 대한 피드백 비트를 나타내고, B는 안테나들의 개수를 나타낸다.In Equation 1 above,

denotes a multiple input single output (MISO, hereinafter referred to as "MISO") channel vector,

denotes a unit norm beamforming codeword, denotes a feedback bit for an RVQ codebook, and B denotes the number of antennas.

Then, with reference to FIG. 1, a feedback overhead according to the number of general massive MIMO antennas will be described.

1 is a graph schematically illustrating feedback overhead according to the number of general massive MIMO antennas.

Referring to FIG. 1 , the horizontal axis indicates the number of transmit antennas, and the vertical axis indicates the number of bits required for feedback. In addition, curves representing the feedback overheads according to the number of massive MIMO antennas in FIG. 1 are, respectively, the target gain (target gain: G _target ) of the massive MIMO antennas in the case of 0.5 and 0.6, 0.7 and 0.8. It should be noted that these are curves representing feedback overheads according to the number.

As shown in FIG. 1 , it can be seen that the feedback overhead increases in proportion to the number of antennas. Such a huge feedback overhead places an unnecessary burden on the feedback links.

Accordingly, there is a need for a method for performing a beamforming operation to reduce feedback overhead in a communication system supporting the FD-MIMO scheme.

On the other hand, the above information is only presented as background information to help the understanding of the present invention. No decision has been made, nor is any claim made as to whether any of the above is applicable as prior art to the present invention.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation in a communication system supporting an FD-MIMO scheme.

In addition, an embodiment of the present invention proposes an apparatus and method for performing a beamforming operation based on a Kronecker product mono codebook and a Kronecker product double codebook in a communication system supporting the FD-MIMO scheme.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation based on channel characteristics in a communication system supporting an FD-MIMO scheme.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation based on an antenna structure in a communication system supporting an FD-MIMO scheme.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation to reduce feedback overhead in a communication system supporting an FD-MIMO scheme.

The method proposed in one embodiment of the present invention is; In a method of performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, a rough beam of a first dominant beam the process of detecting detecting at least two codeword candidates based on the coarse beam of the first dominant beam; and selecting one of the at least two codeword candidates as a final codeword.

Another method proposed in an embodiment of the present invention is; In a method of performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, at least two wide resource blocks (RBs) detecting at least two beams for each; detecting at least two codeword candidates for each of the narrow RBs based on the detected at least two beams; and selecting one of the at least two codeword candidates as a final codeword.

An apparatus proposed in an embodiment of the present invention includes; In an apparatus for performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, a rough beam of a first dominant beam A controller performing an operation of detecting , detecting at least two codeword candidates based on the coarse beam of the first dominant beam, and selecting one of the at least two codeword candidates as a final codeword It is characterized in that it includes.

Another device proposed in an embodiment of the present invention is; In an apparatus for performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, at least two wide resource blocks (RBs) detecting at least two beams for each, detecting at least two codeword candidates for each of narrow RBs based on the detected at least two beams, and one of the at least two codeword candidates and a controller that performs the operation of selecting as the final codeword. Other aspects, benefits and key features of the present invention are addressed in conjunction with the accompanying drawings, which illustrate preferred embodiments of the present invention. It will be apparent to those skilled in the art from the following detailed description, which is disclosed.

Before processing the detailed description part of the present disclosure, it may be effective to establish definitions for specific words and phrases used throughout this patent document: the terms “include” and “ “comprise” and its derivatives mean inclusive indefinitely; the term “or” is inclusive and means “and/or”; The phrases “associated with” and “associated therewith” and their derivatives include, be included within, and interconnect with ( interconnect with, contain, be contained within, connect to or with, couple to or with ), be communicable with, cooperate with, interleave, juxtapose, be proximate to, and likely to means something like be bound to or with, have, have a property of, etc.; The term “controller” means any device, system, or part thereof that controls at least one operation, such a device being hardware, firmware or software, or some combination of at least two of the hardware, firmware or software. can be implemented in It should be noted that the functionality associated with any particular controller may be centralized or distributed, and may be local or remote. Definitions for specific words and phrases are provided throughout this patent document, and those of ordinary skill in the art will in many, if not most cases, apply such definitions to conventional as well as conventional, as well as words and phrases defined above. It should be understood that this also applies to future uses of the phrases.

An embodiment of the present invention has an effect of enabling the beamforming operation to be performed in a communication system supporting the FD-MIMO scheme.

In addition, an embodiment of the present invention has an effect of enabling the beamforming operation to be performed based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting the FD-MIMO scheme.

An embodiment of the present invention has an effect of enabling a beamforming operation to be performed based on a channel characteristic in a communication system supporting the FD-MIMO scheme.

An embodiment of the present invention has an effect of enabling a beamforming operation based on an antenna structure in a communication system supporting the FD-MIMO scheme.

An embodiment of the present invention has an effect of enabling a beamforming operation to be performed so as to reduce a feedback overhead in a communication system supporting the FD-MIMO scheme.

Other aspects, features and benefits as set forth above of certain preferred embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings:
1 is a graph schematically illustrating feedback overhead according to the number of general massive MIMO antennas;
2 is a diagram schematically illustrating a UPA antenna structure in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
3 is a diagram schematically illustrating an experimental CDF of a correlation coefficient in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
4 is a diagram schematically illustrating a snapshot of beam patterns in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
5 is a diagram schematically illustrating a correlation between channels in each reception antenna in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
6 is a diagram schematically illustrating a broadband in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
7 is a diagram schematically illustrating a snapshot of beam patterns of each tone in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention;
8 is a diagram schematically illustrating a correlation between channels in each sub-channel in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
9 is a diagram schematically illustrating an example of a normalized beamforming gain for a Kronecker product mono codebook when a MISO scheme is used in a communication system according to an embodiment of the present invention;
10 is a diagram schematically illustrating another example of a normalized beamforming gain for a Kronecker product mono codebook when a MISO scheme is used in a communication system according to an embodiment of the present invention;
11 is a diagram schematically illustrating an example of a beamforming gain normalized with respect to the number of receive antennas when a MIMO scheme is used in a communication system according to an embodiment of the present invention;
12 is a diagram schematically illustrating another example of a beamforming gain normalized to the number of receive antennas when a MIMO scheme is used in a communication system according to an embodiment of the present invention;
13 is a diagram schematically illustrating an example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention;
14 is a diagram schematically illustrating another example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention;
15 is a diagram schematically illustrating an internal structure of a signal transmission apparatus in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention;
16 is a diagram schematically illustrating an internal structure of a signal receiving apparatus in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.
It should be noted that throughout the drawings, like reference numerals are used to denote the same or similar elements, features, and structures.

BRIEF DESCRIPTION OF THE DRAWINGS The following detailed description with reference to the appended drawings will aid in a comprehensive understanding of various embodiments of the present disclosure, which are defined by the claims and their equivalents. The following detailed description contains various specific details for the purpose of understanding, but this will be regarded as merely examples. Accordingly, those skilled in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

The terms and words used in the following detailed description and claims are not limited to the literal meaning, but are merely used to enable a clear and consistent understanding of the present disclosure by the inventor. Accordingly, for those skilled in the art, the following detailed description of various embodiments of the present disclosure is provided for illustrative purposes only, and defines the present disclosure as defined by the appended claims and their equivalents. It should be clear that it is not provided to do so.

In addition, it will be understood that singular expressions such as "above" and "above" include plural expressions in this specification, unless otherwise clearly indicated. Thus, as an example, a “component surface” includes one or more component representations.

Also, terms including an ordinal number such as first, second, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. and/or includes a combination of a plurality of related listed items or any of a plurality of related listed items.

In addition, the terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in a commonly used dictionary should be understood to have a meaning consistent with the meaning in the context of the related art.

According to various embodiments of the present disclosure, an electronic device may include a communication function. For example, the electronic device includes a smart phone, a tablet personal computer (PC, hereinafter referred to as "PC"), a mobile phone, a video phone, and an e-book reader (e). -book reader), a desktop PC, a laptop PC, a netbook PC, a personal digital assistant (PDA, hereinafter referred to as "PDA") and a portable A portable multimedia player (PMP, hereinafter referred to as “PMP”), an mp3 player, a mobile medical device, a camera, and a wearable device (eg, a head-mounted device) A head-mounted device (HMD, for example, will be referred to as 'HMD'), electronic clothing, electronic bracelets, electronic necklaces, electronic accessories, electronic tattoos, or smart watches ), and so on.

According to various embodiments of the present disclosure, the electronic device may be a smart home appliance having a communication function. For example, the smart home device includes a TV, a digital video disk (DVD, hereinafter referred to as "DVD") player, audio, a refrigerator, an air conditioner, a vacuum cleaner, an oven, A microwave oven, a washer, a dryer, an air purifier, a set-top box, a TV box (eg, Samsung HomeSync ^TM , Apple TVTM, or Google TV ^TM ), and a game console ( gaming consoles), electronic dictionaries, camcorders, electronic photo frames, and the like.

According to various embodiments of the present disclosure, an electronic device includes a medical device (eg, a magnetic resonance angiography (MRA)) device, a magnetic resonance imaging (MRA) device, and a magnetic resonance imaging (MRA) device. : MRI, hereinafter referred to as “MRI”), a computed tomography (CT, hereinafter referred to as “CT”) device, an imaging device, or an ultrasound device), and a navigation device; , a global positioning system (GPS, hereinafter referred to as "GPS") receiver, an event data recorder (EDR, hereinafter referred to as "EDR"), and a flight data recorder (hereinafter referred to as "EDR"); recorder: FDR, hereinafter referred to as "FER"), an automotive infotainment device, a navigation electronic device (eg, a navigation navigation device, a gyroscope, or a compass), and an avionics device and security devices, industrial or consumer robots, and the like.

According to various embodiments of the present invention, an electronic device includes furniture, a part of a building/structure, an electronic board, an electronic signature receiving device, a projector, and various measurement devices (eg, water, electricity, gas or electromagnetic wave measurement devices), and the like.

According to various embodiments of the present invention, the electronic device may be a combination of devices as described above. In addition, it will be apparent to those skilled in the art that the electronic device according to preferred embodiments of the present invention is not limited to the device described above.

An embodiment of the present invention provides an apparatus and method for performing a beamforming operation in a communication system supporting a (frequency division-multiple input multiple output: FD-MIMO, hereinafter referred to as "FD-MIMO") scheme suggest

In addition, an embodiment of the present invention performs a beamforming operation based on a Kronecker-product mono codebook and a Kronecker product dual in a communication system supporting the FD-MIMO scheme. Apparatus and methods are proposed.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation based on channel characteristics in a communication system supporting an FD-MIMO scheme.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation based on an antenna structure in a communication system supporting an FD-MIMO scheme.

An embodiment of the present invention proposes an apparatus and method for performing a beamforming operation to reduce a feedback overhead in a communication system supporting an FD-MIMO scheme.

On the other hand, the apparatus and method proposed in an embodiment of the present invention include a long-term evolution (LTE, hereinafter referred to as "LTE") mobile communication system and a long-term evolution-advanced (long-term evolution) -Advanced: LTE-A, hereinafter referred to as "LTE-A") a mobile communication system, and a licensed-assisted access (LAA, hereinafter referred to as "LAA")-LTE mobile communication system; , high speed downlink packet access (HSDPA, hereinafter referred to as "HSDPA") mobile communication system, and high speed uplink packet access (HSUPA, hereinafter referred to as "HSUPA") The mobile communication system and the 3rd generation project partnership 2 (3rd generation partnership project 2: 3GPP2, hereinafter referred to as "3GPP2") of high rate packet data (high rate packet data: HRPD, hereinafter referred to as "HRPD") A mobile communication system, a 3GPP2 wideband code division multiple access (WCDMA, hereinafter referred to as "WCDMA") mobile communication system, and a 3GPP2 code division multiple access (CDMA) , hereinafter referred to as "CDMA") a mobile communication system, the International Institute of Electrical and Electronics Engineers (IEEE, hereinafter referred to as "IEEE") 802.16m communication system, and an evolved packet system ( evolved packet system: EPS, hereinafter referred to as "EPS") and mobile internet protocol: Mobil e IP, hereinafter referred to as "Mobile IP") can be applied to various communication systems, such as a system.

First, a system model considered in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described.

에 의해 정의된다. First, in an embodiment of the present invention, a MIMO scheme using M transmit antennas and N receive antennas will be considered. Here, a radio channel between each of the M transmit antennas and each of the N receive antennas is a channel vector.

is defined by

On the other hand, a cellular system supporting a frequency division duplexing (FDD, hereinafter referred to as "FDD") method estimates a channel at the receiver side and quantizes the estimated channel to obtain channel state information (channel state information). : CSI, hereinafter referred to as "CSI") and feeds back the generated CSI to the transmitter through a feedback link.

In addition, a system supporting a massive MIMO (massive MIMO, hereinafter referred to as “massive MIMO”) method has a large-scale (hereinafter referred to as “large-scale”) feedback in order to accurately quantize a channel. You need to have overhead. However, it is difficult to realize with large-scale feedback overhead in a general cellular system due to practical issues such as the complexity of codeword search and feedback overhead.

Therefore, the codebook for the massive MIMO scheme needs to be designed using the antenna structure and channel characteristics.

Next, an antenna structure considered in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described.

First, the effect of the antenna structure will be described as follows.

Since the massive MIMO method generally uses a plurality of antennas, for example, more than 100 antennas, it is necessary to arrange the antennas to have space efficiency. Accordingly, in one embodiment of the present invention, a unitary planar array (UPA, hereinafter referred to as "UPA") will be considered in order to arrange a plurality of antennas in a limited space.

First, M _v in the vertical and horizontal domains, respectively A UPA antenna structure in which N transmit antennas and M _h transmit antennas are disposed, and N _v receive antennas and N _h receive antennas are disposed in a vertical area and a horizontal area, respectively, will be considered. This will be described with reference to FIG. 2 as follows.

2 is a diagram schematically illustrating a UPA antenna structure in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention.

개의 송신 안테나들을 포함하고, 수신기(213)가

개의 수신 안테나들을 가진다 도 2에서, d_v 및 d_h는 각각 수평 라인 및 수직 라인에서의 안테나 엘리먼트(antenna element)들간의 간격을 나타낸다.Referring to FIG. 2 , in the UPA antenna structure shown in FIG. 2 , M _v transmit antennas and M _h transmit antennas are disposed in a vertical area and a horizontal area, respectively, and N _v receive antennas are respectively disposed in a vertical area and a horizontal area. Antennas and N _h receive antennas are deployed. That is, as shown in FIG. 2 , the UPA antenna structure is the transmitter 211

including transmit antennas, and the receiver 213

In FIG. 2 , d _v and d _h denote intervals between antenna elements in a horizontal line and a vertical line, respectively.

On the other hand, a ray-like (hereinafter, referred to as “ray-like”) beam having a UPA antenna structure may be defined as in Equation 2 below by the Kronecker product of array response vectors. can

는 수직 영역에서의 어레이 응답 벡터들의 각도들을 나타내고,

는 수평 영역에서의 어레이 응답 벡터들의 각도들을 나타낸다. In Equation 2, λ represents the wavelength,

denotes the angles of the array response vectors in the vertical domain,

denotes the angles of the array response vectors in the horizontal domain.

의 DFT 코드북은 하기 수학식 3과 같이 정의될 수 있다.On the other hand, the Kronecker product codebook may be a promising candidate representing channels occurring in the UPA antenna structure. In addition, a set of discrete Fourier transform (DFT, hereinafter referred to as "DFT") vectors is suitable for quantizing ray-like beams that can be defined by array response vectors. Accordingly, in an embodiment of the present invention, Kronecker product codebooks using DFT vectors will be considered. Here, the size

The DFT codebook of can be defined as in Equation 3 below.

Next, characteristics of a three-dimensional (3D, hereinafter referred to as "3D") spatial channel model (SCM, hereinafter referred to as "SCM") will be described.

The 3D SCM can be expressed as Equation 4 below.

은 블록 페이딩(block fading) 다중 입력 단일 출력(multiple input single output: MISO, 이하 "MISO"라 칭하기로 한다) 채널 벡터를 나타내고,

및

각각은 어레이 응답 벡터를 나타내고, a_k 는 k번째 ray-like빔의 복소 채널 이득을 나타내고, a_p는 p번째 DFT 빔에 대한 채널 이득을 나타내고, c_vp 는 수직 영역에서 p번째 DFT 빔에 대한 DFT 벡터를 나타내고, c_hp 는 수평 영역에서의 p번째 DFT 빔에 대한 DFT 벡터를 나타내고, P는 사용된 DFT 빔들의 개수를 나타내고,

은 대략적으로 계산된 채널 벡터를 나타낸다. The 3D SCM as shown in Equation 4 is a 3D SCM roughly calculated using a finite number of DFT beams. In addition, in Equation 4,

represents a block fading multiple input single output (MISO, hereinafter referred to as "MISO") channel vector,

and

Each represents an array response vector, a _k represents the complex channel gain of the k-th ray-like beam, a _p represents the channel gain for the p-th DFT beam, and c _vp represents the p-th DFT beam in the vertical domain. represents the DFT vector, c _hp denotes the DFT vector for the p-th DFT beam in the horizontal domain, P denotes the number of used DFT beams,

denotes an approximate calculated channel vector.

In order to evaluate the accuracy of the roughly calculated channel vector, a correlation coefficient is defined as in Equation 5 below.

The correlation coefficient as shown in Equation 5 above is detected from numerical simulations with 5,000 independent 3D SCM channel realizations as an example.

Then, here, with reference to FIG. 3, an empirical cumulative distribution function (CDF, hereinafter referred to as "CDF") of a correlation coefficient in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention. to explain

3 is a diagram schematically illustrating an experimental CDF of a correlation coefficient in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 3 , simulation parameters used to detect the experimental CDF of the correlation coefficient shown in FIG. 3 may be shown in Table 1 below.

In FIG. 3 , P may be any one of 1, 2, and 3, and B may be any one of 5 or 6. In Table 1, P denotes the number of used DFT beams, and B denotes the size of the used DFT codebook.

In FIG. 3 , the horizontal axis represents the correlation coefficient X, and the vertical axis represents F(X), which is an experimental CDF with the correlation coefficient X as an input. As shown in Fig. 3, roughly calculated channel vectors with 1, 2 and 3 DFT beams, defined on the basis of DFT codebooks of size 2 ⁵ , respectively during time, i.e. 70% of the channel realization It can be seen that it produces correlation coefficients greater than 0.425, 0.63 and 0.72. Here, the roughly calculated channel vectors, defined based on the size 2 ⁶ DFT codebooks, generate correlation coefficients of 0.43, 0.64, and 0.73 or more, respectively, for 70% of the time.

Here, the expected value of the correlation coefficient X can be expressed as in Equation 6 below.

The expected value of the correlation coefficient X as shown in Equation ⁶ is 0.5808, 0.7248, and 0.5808, 0.7248, and becomes 0.7799, 2 ⁶ In the case of the codebook scenario of magnitude, it becomes 0.5913, 0.7362, and 0.7924 for roughly calculated channel vectors with 1, 2 and 3 DFT beams.

As shown in Fig. 3, the combination of a finite number of DFT beams would be a promising solution for representing channel vectors. Here, it should be noted that quantization performance may be improved when a larger number of DFT beams are considered.

However, in an embodiment of the present invention, two DFT beams are considered in consideration of practical issues such as complexity and feedback overhead for codeword search.

Accordingly, the codebooks proposed in an embodiment of the present invention search and combine two DFT beams to quantize 3D SCM channels.

First, a beam search method for general Kronecker product codebooks will be described as follows.

Common Kronecker product codebooks decompose a channel vector based on a singular value decomposition method. Here, the decomposed channel vector can be expressed as in Equation 7 below.

은 MISO 채널 벡터를 나타내고,

는 k번째 도미넌트(dominant) 좌(left) 특이 벡터를 나타내고,

은 k번째 도미넌트 우(right) 특이 벡터를 나타내고,

는 k 번째 특이 값(singular value)을 나타낸다. In Equation 7 above,

denotes the MISO channel vector,

represents the kth dominant left singular vector,

denotes the kth dominant right singular vector,

denotes the k-th singular value.

To express h , general Kronecker product codebooks are a first dominant left singular vector and a first dominant right singular vector in a vertical domain and a horizontal domain, for example, u ₁ and quantize v ₁ . And, the selected codeword can be expressed as in Equation 8 below.

의 DFT 코드북을 나타내며, C_hb 는 수평 방향에서 크기

의 DFT 코드북을 나타낸다. 그리고 나서, DFT 벡터들이 최종 코드워드를 생성하기 위해 결합된다. 상기 최종 코드워드는 하기 수학식 9와 같이 나타낼 수 있다.In Equation 8, C _vb is the magnitude in the vertical direction

denotes the DFT codebook of C _hb is the magnitude in the horizontal direction

represents the DFT codebook of . The DFT vectors are then combined to generate the final codeword. The final codeword may be expressed as in Equation 9 below.

First, general Kronecker product codebooks do not directly quantize a channel. The Kronecker product codebooks consider only the first dominant singular vector in the vertical domain and the first dominant singular vector in the horizontal domain. However, considering only the first dominant singular vectors may not be an efficient solution for constructing the CSI, since DFT beams may not be suitable to represent the first dominant singular vectors. Also, the second dominant DFT beams may not exist in the first dominant subspace in which general codebooks are searching.

Next, general Kronecker product codebooks do not jointly search the vertical domain and the horizontal domain. That is, in general Kronecker product codebooks, each codeword is separately selected in a vertical domain and a horizontal domain. As such, the method of searching for separate codewords in the vertical and horizontal domains, that is, separately searching for beams in the vertical and horizontal domains, is highly unlikely to be an optimal solution.

Finally, a system supporting general Kronecker product codebooks does not consider phase alignment between multiple beams. As an example, general Kronecker product codebooks consider superposition between two beams as shown in Equation 10 below.

In Equation 10, c _v1 denotes a first codeword candidate, and c _v2 denotes a second codeword candidate. As described above, in a system supporting general Kronecker product codebooks, since phase alignment between a plurality of beams is not considered, the phases of the two beams are not properly aligned, and thus the performance of the two beams is deteriorated. can be combined in this way.

As described above, the beam search method for general Kronecker product codebooks may prevent desirable channel quantization. Therefore, in order to quantize a channel for a massive MIMO communication system, in an embodiment of the present invention, new beam search methods for Kronecker product codebooks, for example, a beam search method for Kronecker product mode codebook and Kronecker product We propose a beam search method for a double codebook.

First, a beam search method for the Kronecker product mono codebook will be described.

First, an embodiment of the present invention will consider a single tone block fading channel, that is, a single frequency subcarrier channel. As described in the antenna structure considered in the communication system supporting the FD-MIMO scheme according to an embodiment of the present invention, the channel vector h may be roughly calculated by combining two DFT beams. Accordingly, the beam search method proposed in an embodiment of the present invention selects two DFT beams by jointly searching the vertical and horizontal areas, and combines the selected two DFT beams. Here, in order to reduce the complexity of a codeword search that may be generated when a beam is jointly searched, an embodiment of the present invention provides a hierarchical multi-round beam search scheme, for example, the first round A hierarchical multi-round beam search scheme including a beam search process, a second round beam search process, and a final codeword selection process is used.

First, a first round beam search process will be described.

In a first round beam search process, a user equipment (UE) detects a rough beam direction of a first dominant DFT beam in a channel. Here, the first dominant DFT beam c ₁ may be expressed as in Equation 11 below.

은 블록 페이딩 MISO 채널 벡터이다. 이하, 설명의 편의상 채널 벡터의 서브캐리어 인덱스는 생략하기로 한다.As shown in Equation 11, the first dominant DFT beam c ₁ is the Kronecker product of DFT vectors, ie, c _v1 and c _h1 . here,

is the block fading MISO channel vector. Hereinafter, the subcarrier index of the channel vector will be omitted for convenience of description.

의 DFT 코드북들이다.In addition, in Equation 11, c _v1 and c _h1 are sizes defined by Equation 12 below.

of DFT codebooks.

Here, it should be noted that the DFT beam c ₁ selected in the first round beam search process will be used in the second round beam search process.

Second, a second round beam search process will be described.

In the second round beam search process, the user terminal calculates two codeword candidates based on c ₁ . In an embodiment of the present invention, consider two scenarios in an SCM channel environment, that is, a scenario in which one dominant beam is considered, that is, a first channel scenario and a scenario in which two dominant beams are considered, that is, a second channel scenario. decide to do

First, the first codeword candidate is calculated in consideration of the first channel scenario in which one dominant beam is assumed in the channel. The coarse beam direction of the first dominant beam c ₁ may be modified by searching for adjacent directions of the first dominant beam c 1 . Here, the first codeword candidate c _I may be determined as in Equation 13 below.

는 수직 영역 및 수평 영역에서 쉬프팅(shifting) 각도들, 일 예로

및

를 각각 갖는 어레이 응답 벡터들의 크로네커 곱을 나타내고, Z₂는 첫 번째 도미넌트 빔을 수정하기 위해 설계되는 크기

의 코드북을 나타낸다. In Equation 13,

is the shifting angles in the vertical region and the horizontal region, for example

and

denotes the Kronecker product _of the array response vectors each having

of the codebook.

The codebook Z ₂ can be expressed as in Equation 14 below.

를 사용하는 하다마드 곱(hadamard product) 공식은 수직 영역 및 수평 영역에서 각각

및

의 양만큼 첫 번째 빔 c ₁ 의 빔 방향들을 이동시킨다는 것에 유의하여야만 할 것이다.here,

The Hadamard product formula using

and

It should be noted that it shifts the beam directions of the first beam c ₁ by the amount of .

Next, the second codeword candidate is calculated in consideration of the second channel scenario assuming two dominant beams in the channel. In an embodiment of the present invention, a system supporting the FD-MIMO scheme detects the second dominant DFT beam and jointly combines it with the first dominant DFT beam c ₁ .

은 하기 수학식 15와 같이 나타낼 수 있다.the second codeword candidate

can be expressed as in Equation 15 below.

의 DFT 코드북을 나타내고, Z 는 두 개의 빔들 간의 위상 정렬을 위한 크기

의 코드북을 나타낸다. 여기서, 상기 코드북 Z 는 하기 수학식 16과 같이 나타낼 수 있다.In Equation 15, c _v3 and c _h3 are each a size

represents the DFT codebook of , and Z is the size for phase alignment between two beams.

of the codebook. Here, the codebook Z can be expressed as in Equation 16 below.

와 같이 설정된다는 것에 유의하여야만 할 것이다.Here, the relationship between the feedback overhead for the first codebook candidate and the second codebook candidate is

It should be noted that it is set as

Third, the final codeword selection process will be described.

및 두 번째 코드워드 후보

중 하나로 선택된다. 여기서, 상기 최종 코드워드는 하기 수학식 17과 같이 나타낼 수 있다.First, the final codeword consists of two codeword candidates, namely the first codeword candidate.

and second codeword candidate

one of them is selected Here, the final codeword can be expressed as in Equation 17 below.

Second, a beam search method for a Kronecker product mono codebook for a plurality of receive antennas will be described.

First, before describing a beam search method for a Kronecker product mode codebook for a plurality of receive antennas, in an embodiment of the present invention, channel characteristics of a MISO channel vector in each of the receive antennas are analyzed.

In particular, in an embodiment of the present invention, it is possible to detect a correlation between MISO channel vectors in each of the receiving antennas based on FIGS. 4 and 5 , which will be described in detail as follows.

First, a snapshot of beam patterns in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described with reference to FIG. 4 .

4 is a diagram schematically illustrating a snapshot of beam patterns in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 4 , it is first assumed that M _v x M _h = 10 x 10 transmit antennas and N _v x N _h = 2 X 1 receive antennas are used in a communication system supporting the FD-MIMO scheme. do it with In addition, 411 indicates a snapshot of the beam pattern of the first reception antenna among the N _v x N _h = 2 x 1 reception antennas, and 413 indicates two of the N _v x N _h = 2 x 1 reception antennas. A snapshot of the beam pattern of the th reception antenna is shown.

In FIG. 4, a snapshot of beam patterns in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention has been described. Next, with reference to FIG. 5, the FD-MIMO scheme according to an embodiment of the present invention. Correlation between channels in each receiving antenna in a communication system supporting .

5 is a diagram schematically illustrating a correlation between channels in each reception antenna in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 5 , it is first assumed that M _v x M _h = 10 x 10 transmit antennas and N _v x N _h = 2 x 1 receive antennas are used in a communication system supporting the FD-MIMO scheme. do it with In addition, in FIG. 5 , the horizontal axis indicates the number of transmit antennas, M _v x M _h , and the vertical axis indicates a correlation coefficient.

As shown in FIG. 5 , it can be seen that the beam direction in each receiving antenna has a high correlation, but the normalized channels do not have a high correlation. Here, the correlation channel characteristic enables codebooks supporting a plurality of receive antennas to use the hierarchical multi-round beam search scheme.

On the other hand, in a MIMO system using a plurality of receive antennas, an embodiment of the present invention also needs to consider combining at the receiver side.

Here, the optimization problem can be expressed as Equation 18 below.

는 선택된 결합 코드워트 벡터를 나타내고,

는 선택된 빔포밍 코드워드 벡터를 나타내고,

는 N개의 MISO 채널 벡터

를 포함하는 블록 페이딩 MIMO 채널 행렬을 나타낸다.In Equation 18,

denotes the selected joint codeword vector,

represents the selected beamforming codeword vector,

is a vector of N MISO channels

It represents a block fading MIMO channel matrix including

를 사용하기로 한다. 이때, 상기 최적화 문제는 하기 수학식 19와 같이 표현될 수 있다.In one embodiment of the present invention, a maximum ratio combiner is used to maximize an effective signal to noise ratio (SNR, hereinafter referred to as "SNR").

decide to use In this case, the optimization problem may be expressed as Equation 19 below.

을 사용하여

로 정의될 수 있음에 유의하여야만 한다. 마찬가지로, 빔포밍 코드워드

는 최대화 문제에서의 메트릭(metric)을 제외하고, 크로네커 곱 모노 코드북에 대한 빔 검색 방법에서 설명된 바와 같이 크로네커 곱 모노 코드북을 기반으로 선택된다.On the other hand, the combiner at the receiver side selects the beamforming codeword

using

It should be noted that it can be defined as Similarly, beamforming codewords

, except for the metric in the maximization problem, is selected based on the Kronecker product mono codebook as described in the beam search method for the Kronecker product mono codebook.

Third, a beam search method for the Kronecker product double codebook will be described.

An embodiment of the present invention proposes Kronecker product duplex codebooks supporting a plurality of tones, ie, sub-carriers, in a wideband. Before describing a beam search method for Kronecker product duplex codebooks, an embodiment of the present invention first defines the entire range of a wideband.

와 같이 L개의 넓은 리소스 블록(resource block: RB, 이하 "RB"라 칭하기로 한다)들로 구분된다. 여기서, 넓은 RB는 하기 수학식 20과 같이 표현될 수 있다.First, a broadband containing C tones is

It is divided into L wide resource blocks (resource blocks: RBs, hereinafter referred to as "RBs") as shown in FIG. Here, the wide RB may be expressed as in Equation 20 below.

In Equation 20, H ₁ represents the l-th wide RB including C/L tones.

와 같이R 개의 좁은 RB들로 구분된다. 여기서, 좁은 RB는 하기 수학식 21과 같이 표현될 수 있다.Next, each wide RB is

It is divided into R narrow RBs as shown. Here, the narrow RB may be expressed as in Equation 21 below.

In Equation 21, H _l [r] represents the r-th narrow RB including C/(LR) channel tones in the l-th wide RB.

In an embodiment of the present invention, it is assumed that each wide RB has a wideband precoding matrix indicator (PMI, hereinafter referred to as “PMI”), and each narrow RB has a narrowband PMI. do.

Then, with reference to FIG. 6, the broadband in the communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described as follows.

6 is a diagram schematically illustrating a broadband in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

와 같이 L개의 넓은 RB들을 포함하고, 각각의 넓은 RB는

와 같이 R개의 좁은 RB들을 포함한다.Referring to FIG. 6 , a broadband including C tones is

Including L wide RBs, each wide RB is

It includes R narrow RBs as

Meanwhile, in an embodiment of the present invention, channel characteristics of a plurality of tones are considered.

First, a snapshot of beam patterns of each tone in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described with reference to FIG. 7 .

7 is a diagram schematically illustrating a snapshot of beam patterns of each tone in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 7 , it is first assumed that M _v x M _h = 10 x 10 transmit antennas and N _v x N _h = 2 x 1 receive antennas are used in a communication system supporting the FD-MIMO scheme. do it with In addition, 711 indicates a snapshot for the beam pattern of the first subcarrier, 713 indicates a snapshot for the beam pattern of the tenth subcarrier, 715 indicates a snapshot for the beam pattern of the 37th subcarrier, 717 represents a snapshot of the beam pattern of the 46th subcarrier.

As shown in FIG. 7 , it can be seen that the beam direction in each subcarrier has a high correlation.

In FIG. 7, a snapshot of beam patterns of each tone in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention has been described. Next, with reference to FIG. 8, FD according to an embodiment of the present invention - Correlation between channels in each sub-channel in a communication system supporting the MIMO method will be described.

8 is a diagram schematically illustrating a correlation between channels in each subchannel in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 8, first, in a communication system supporting the FD-MIMO scheme, M _v x M _h = 10 x 10 transmit antennas are used, N _v x N _h = 2 x 1 receive antennas are used, and It is assumed that the number C is 300 (C = 300). In addition, in FIG. 8 , the horizontal axis represents the number of transmit antennas, M _v It represents x M _h , and the vertical axis represents the correlation coefficient.

As shown in FIG. 8 , it can be seen that the DFT beam directions in each subcarrier are highly correlated, but the normalized channels are not highly correlated.

Accordingly, an embodiment of the present invention proposes dual codebooks sharing some correlation information, such as coarse beam directions for wide RBs, in order to reduce the overall feedback overhead.

Hereinafter, the beam search method for the Kronecker product double codebook proposed in an embodiment of the present invention will be described in detail. The beam search method for the Kronecker product double codebook is a first round method for wide RBs. It includes a beam search process, a second round beam search process for narrow RBs, and a final codeword selection process. First, a first round beam search process for wide RBs will be described.

First, in a first round beam search process for wide RBs, a user terminal detects coarse beam directions for wide RBs. Here, in consideration of a limited amount of feedback overhead, a communication system supporting the FD-MIMO scheme detects only two beams for each wide RB in the first round beam search process for the wide RBs.

은 하기 수학식 22와 같이 나타낼 수 있다.1st dominant DFT beam for lth wide RB

can be expressed as in Equation 22 below.

의 DFT 코드북을 나타낸다. 여기서, C_vW1는 수직 영역에서 크기

의 DFT 코드북을 나타내고, C_hW1는 수평 영역에서 크기

의 DFT 코드북을 나타낸다.In Equation 22 , H ₁ represents a channel matrix for the l-th wide RB including C/L channel tones, and C _vW1 and C _hW1 have sizes, respectively.

represents the DFT codebook of . where C _vW1 is the magnitude in the vertical domain

denotes the DFT codebook of , and C _hW1 is the size in the horizontal domain.

represents the DFT codebook of .

은 하기 수학식 23과 같이 나타낼 수 있다.Next, the second dominant DFT beam

can be expressed as in Equation 23 below.

의 DFT 코드북을 나타낸다. 여기서, C_vW2는 수직 영역에서 크기

의 DFT 코드북을 나타내고, 는C_hW2 수평 영역에서 크기

의 DFT 코드북을 나타낸다. 여기서, 두 개의 선택된 빔들은 다음 프로세스, 즉 좁은 RB들에 대한 제2 라운드 빔 검색 프로세스에서 최종 코드워드를 선택하기 위해 좁은 RB들 사이에서 공유될 것이다. 여기서, 넓은 RB들에 대한 두 개의 개략적 빔들의 집합은 광대역 PMI로 간주될 수 있음에 유의하여야만 한다.In Equation 23, C _vW2 and C _hW2 are each a size

represents the DFT codebook of . where C _vW2 is the magnitude in the vertical domain

denotes the DFT codebook of , and C _hW2 magnitude in the horizontal domain.

represents the DFT codebook of . Here, the two selected beams will be shared among the narrow RBs to select the last codeword in the next process, that is, the second round beam search process for the narrow RBs. Here, it should be noted that the aggregation of two coarse beams for wide RBs can be regarded as a wideband PMI.

Second, a second round beam search process for narrow RBs will be described.

및

을 기반으로 하여 각각의 좁은 RB에 대한 두 개의 코드워드 후보들을 계산한다. First, in the second round beam search process for narrow RBs, the user terminal detects the detected wide RBs for wide RBs.

and

Two codeword candidates for each narrow RB are calculated based on .

In an embodiment of the present invention, two scenarios will be considered in an SCM channel environment, that is, a scenario in which one dominant beam is used and a scenario in which two dominant beams are used.

은 하기 수학식 24와 같이 표현될 수 있다.The first codeword candidate is calculated considering a scenario in which one beam is used. Here, the first beam defined for wide RBs

can be expressed as in Equation 24 below.

는 l 번째 넓은 RB에서의 r 번째 좁은 RB에 대한 채널 행렬을 나타내고, Z_N1은 첫 번째 빔을 수정하기 위해 설계되는 크기

의 코드북을 나타낸다. 여기서, 상기 크기

의 코드북 Z_N1 은 하기 수학식 25와 같이 표현될 수 있다.In Equation 24 above,

denotes the channel matrix for the r-th narrow RB in the l-th wide RB, and Z _N1 is the size designed to modify the first beam.

of the codebook. Here, the size

The codebook Z _N1 of can be expressed as Equation 25 below.

이 수정된 후, 두 번째 빔

과 조인트하게 결합된다. 따라서, 상기 두 번째 코드워드 후보는 하기 수학식 26과 같이 표현될 수 있다.The second codeword candidate is calculated considering a scenario in which two beams are used. first beam

After this fix, the second beam

is jointly coupled with Accordingly, the second codeword candidate may be expressed as in Equation 26 below.

의 코드북을 나타낸다. 상기 크기

의 코드북 Z는 하기 수학식 27과 같이 표현될 수 있다.In Equation 26, Z is the magnitude designed to align the phases of the two beams.

of the codebook. the above size

The codebook Z of can be expressed as Equation 27 below.

와 같이 설정됨에 유의하여야만 할 것이다.The relationship between the feedback codewords for the first codeword candidate and the second codeword candidate is

It should be noted that it is set as

Third, the final codeword selection process will be described.

및 두 번째 코드워드 후보

중 하나로 선택된다. 여기서, 각각의 좁은 RB에 대한 최종 코드워드는 하기 수학식 28과 같이 표현될 수 있다.First, the final codeword consists of two codeword candidates, namely the first codeword candidate.

and second codeword candidate

one of them is selected Here, the final codeword for each narrow RB may be expressed as in Equation 28 below.

Next, the performance of the beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in the communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described.

First, the performance of the Kronecker product mono codebook according to an embodiment of the present invention with respect to one tone will be described as follows. First, in an embodiment of the present invention, a performance metric as shown in Equation 29 below, That is, a normalized beamforming gain is considered.

는 선택된 결합 빔 포밍 코드워드 벡터를 나타내고,

는 선택된 빔포밍 코드워드 벡터를 나타내고,

은 블록 페이딩 MIMO 채널 행렬을 나타낸다. In Equation 29,

denotes the selected combined beamforming codeword vector,

represents the selected beamforming codeword vector,

denotes a block fading MIMO channel matrix.

When the MISO method is used, the normalized beamforming gain may be expressed as Equation 30 below.

은 블록 페이딩 MISO 채널 벡터를 나타낸다.In Equation 30,

denotes a block fading MISO channel vector.

On the other hand, the numerical results can be averaged from the Monte Carlo simulation by realizing 3,000 independent 3D SCM channels.

The number of transmit antennas in which the 3D SCM simulation parameters as described in Table 1 are changed from 4X4 (=16) to 20X20 (=400) and 1X1 (=1) to 2X2 (=4) transmit antennas The same except for the number is used in the Monte Carlo simulation.

In addition, feedback overhead schemes for the Kronecker product mono codebooks proposed in an embodiment of the present invention may be expressed as shown in Table 2 below.

First, the final feedback overhead methods are the first round beam search method included in the beam search method for the Kronecker product mono codebook and the second round beam search process included in the beam search method for the Kronecker product mono codebook. It should be noted that the beam search method for the Kronecker product mono codebook is a combination of the final codeword selection process included.

As shown in Table 2 above, the feedback overhead for the beam search method for the Kronecker product mono codebook includes the feedback overhead for the first round beam search process included in the beam search method for the Kronecker product mono codebook, and Krone Combination of the feedback overhead for the second round beam search process included in the beam search method for the Kerr product mono codebook and the feedback overhead for the final codeword selection process included in the beam search method for the Kronecker product mono codebook it can be seen that

Next, an example of a normalized beamforming gain for the Kronecker product mono codebook when the MISO method is used in the communication system according to an embodiment of the present invention will be described with reference to FIG. 9 .

9 is a diagram schematically illustrating an example of a normalized beamforming gain for a Kronecker product mono codebook when the MISO method is used in a communication system according to an embodiment of the present invention.

Referring to FIG. 9, first, "Mi: B _M =23 bits", "M-ii: B _M =21 bits", and "M-iii: B _M =19 bits" are graphs shown. Each of these represents the normalized beamforming gain of the Kronecker product mono codebook proposed in an embodiment of the present invention, and the graph shown as “Enhanced KP: B _M =24 bits” is the first dominant singularity in the vertical domain. It considers only the vector and the first dominant singular vector in the horizontal domain, and represents the normalized beamforming gain of the Kronecker product codebook that quantizes the two beams present in the channel, as "KP codebook: B _M =24 bits" The graph shown shows the normalized beamforming gain of a general Kronecker product codebook. Hereinafter, for convenience of description, only the first dominant singular vector in the vertical domain and the first dominant singular vector in the horizontal domain are considered, and A Kronecker product codebook that quantizes the existing two beams will be referred to as an "enhanced Kronecker product codebook".

On the other hand, the codebook proposed in an embodiment of the present invention directly quantizes the channel while jointly searching the vertical domain and the horizontal domain, whereas the enhanced Kronecker product codebook and the general Kronecker product codebook have the first dominant singularity in the vertical domain. Only the first dominant singular vector in the vector and horizontal domain is considered.

In addition, the general Kronecker product codebook quantizes only one beam existing in a channel, and the enhanced Kronecker product codebook quantizes two beams, but does not consider phase alignment between multiple beams, so the phases of the two beams are not considered. are not properly aligned, so the two beams can be combined in a way that degrades their performance. In contrast, in the codebook proposed in an embodiment of the present invention, two beams may be combined based on a method of aligning phases.

In particular, the performance graphs shown in FIG. 9 use the MISO method in the communication system, and d _V = 0.8λ, and performance graphs for d _h = 0.5λ are shown.

Also, in FIG. 9 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 9 , the normalized beamforming gains of the Kronecker product mono codebooks proposed in an embodiment of the present invention are the normalized beamforming gain of the general Kronecker product codebook and the normalized Kronecker product codebook of the improved Kronecker product codebook. It can be seen that the performance is excellent compared to the beamforming gain.

In addition, as shown in FIG. 9 , the total feedback overhead for the Kronecker product mono codebooks proposed in an embodiment of the present invention is the total feedback overhead of the general Kronecker product codebook and the total feedback overhead of the enhanced Kronecker product codebook. It can be seen that the feedback overhead is smaller.

In FIG. 9, an example of a normalized beamforming gain for a Kronecker product mono codebook when the MISO method is used in a communication system according to an embodiment of the present invention has been described. Next, with reference to FIG. 10, the present invention Another example of the normalized beamforming gain for the Kronecker product mono codebook when the MISO method is used in the communication system according to an embodiment will be described.

10 is a diagram schematically illustrating another example of a normalized beamforming gain for a Kronecker product mono codebook when the MISO method is used in a communication system according to an embodiment of the present invention.

Referring to FIG. 10, first, each of the graphs shown as "Mi: B _M =23 bits", "M-ii: B _M =21 bits", and "M-iii: B _M =19 bits" is It represents the normalized beamforming gain of the Kronecker product mono codebook proposed in an embodiment of the present invention, and the graph shown as “Enhanced KP: B _M =24 bits” is the normalized beamforming gain of the enhanced Kronecker product codebook. , and a graph shown as “KP codebook: B _M =24 bits” shows the normalized beamforming gain of a general Kronecker product codebook.

In particular, the performance graphs shown in FIG. 10 represent performance graphs when the MISO method is used in the communication system, d _V = 1.6λ, and d _h = 1.0λ.

Also, in FIG. 10 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 10 , the normalized beamforming gains of the Kronecker product mono codebooks proposed in an embodiment of the present invention are the normalized beamforming gain of the general Kronecker product codebook and the normalized Kronecker product codebook of the improved Kronecker product codebook. It can be seen that the performance is excellent compared to the beamforming gain.

In addition, as shown in FIG. 10, the total feedback overhead for the Kronecker product mono codebooks proposed in an embodiment of the present invention is the total feedback overhead of the general Kronecker product codebook and the total feedback overhead of the enhanced Kronecker product codebook. It can be seen that the feedback overhead is smaller.

In FIG. 10, another example of the normalized beamforming gain for the Kronecker product mono codebook when the MISO method is used in the communication system according to an embodiment of the present invention has been described. Next, with reference to FIG. 11, the present invention An example of a beamforming gain normalized with respect to the number of reception antennas when a MIMO scheme is used in a communication system according to an embodiment will be described.

11 is a diagram schematically illustrating an example of a beamforming gain normalized with respect to the number of reception antennas when a MIMO scheme is used in a communication system according to an embodiment of the present invention.

Referring to FIG. 11 , first, a graph shown as “M-iii: N _v x N _h = 2 x 2” is normalized when two receive antennas are used in a vertical region and two receive antennas are used in a horizontal region. Normalization when one receive antenna is used in the vertical domain and two receive antennas are used in the horizontal domain, the graph shown as "M-iii: N _v x N _h = 1 x 2" represents the obtained beamforming gain, "M-iii: N _v x N _h = 2 x 1" represents the normalized beamforming gain when two receive antennas are used in the vertical domain and one receive antenna is used in the horizontal domain, "M-iii: N _v x N _h = 1 x 1" represents a normalized beamforming gain when one receive antenna is used in the vertical region and one receive antenna is used in the horizontal region.

In particular, the performance graphs shown in FIG. 11 show performance graphs when the MIMO scheme is used in the communication system, d _V = 0.8λ, and d _h = 0.5λ.

In addition, in FIG. 11 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 11 , when the MIMO scheme is used, it can be seen that the normalized beamforming gain for the receive antennas increases as the number of receive antennas increases.

In FIG. 11, an example of a beamforming gain normalized with respect to the number of reception antennas when the MIMO scheme is used in a communication system according to an embodiment of the present invention has been described. Next, with reference to FIG. 12, an example of the present invention Another example of a beamforming gain normalized with respect to the number of reception antennas when a MIMO scheme is used in a communication system according to an embodiment will be described.

12 is a diagram schematically illustrating another example of a beamforming gain normalized with respect to the number of receive antennas when a MIMO scheme is used in a communication system according to an embodiment of the present invention.

Referring to FIG. 12 , the graph shown as “M-iii: N _v x N _h = 2 x 2” is normalized when two receive antennas are used in a vertical region and two receive antennas are used in a horizontal region. represents the obtained beamforming gain, "M-iii: N _v The graph shown as x N _h = 1 x 2" represents the normalized beamforming gain when one receive antenna is used in the vertical domain and two receive antennas are used in the horizontal domain, "M-iii: N _v It represents the normalized beamforming gain when two receive antennas are used in the vertical region and one receive antenna is used in the horizontal region, which is shown as x N _h = 2 x 1", "M-iii: N _v x N It represents a normalized beamforming gain when one receive antenna is used in a vertical region and one receive antenna is used in a horizontal region, shown as _h = 1 x 1".

In particular, the performance graphs shown in FIG. 12 show performance graphs when the MIMO scheme is used in the communication system, d _V = 1.6λ, and d _h = 1.0λ.

In addition, in FIG. 12 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 12 , when the MIMO scheme is used, it can be seen that the normalized beamforming gain for the receive antennas increases as the number of receive antennas increases.

Next, the performance of the beamforming operation based on the Kronecker product double codebook in the communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described.

First, in an embodiment of the present invention, a performance metric as shown in Equation 31 below, that is, a normalized beamforming gain will be considered.

은 c 번째 주파수 톤에 대한 MISO 채널 벡터를 나타내고,

은 크로네커 곱 이중 코드북에 대한 빔 검색 방법이 포함하는 최종 코드워드 선택 프로세스에서의 각각의 좁은 RB에 대해 설계되는 선택된 빔포밍 코드워드 벡터를 나타낸다. In Equation 31 above,

denotes the MISO channel vector for the c-th frequency tone,

denotes the selected beamforming codeword vector designed for each narrow RB in the final codeword selection process that the beam search method for the Kronecker product double codebook includes.

It should be noted that one embodiment of the present invention considers C = 600 channel tones for simulations.

The feedback overhead schemes for the Kronecker product double codebooks proposed in an embodiment of the present invention can be summarized as shown in Table 3 below.

As shown in Table 3 above, the feedback overhead for the beam search method for the Kronecker product double codebook is the feedback for the first round beam search process for wide RBs included in the beam search method for the Kronecker product double codebook. The overhead, the feedback overhead for the second round beam search process for narrow RBs included in the beam search method for the Kronecker product double codebook, and the final code included in the beam search method for the Kronecker product double codebook It can be seen that this is a combination of the feedback overhead for the word selection process.

Meanwhile, a simulation method for a beam search method for a Kronecker product single codebook and a double codebook is shown in Table 4 below.

In Table 4, it should be noted that when the LTE scheme of scheme D1 is used, the first 8 narrow RBs include 72 tones, and the ninth narrow RB includes 24 tones.

Next, an example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention will be described with reference to FIG. 13 . do it with

13 is a diagram schematically illustrating an example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention.

13, first, "D1-I: B _D =83 bits", "D2-I: B _D =102 bits", "D3-I: B _D =136 bits", and "D1-II : B _D =65 bits", "D2-II: B _D =90 bits", and "D3-II: B _D = 120 bits" are each of the graphs proposed in an embodiment of the present invention. Represents the normalized beamforming gain of the Kronecker product double codebook, "M1-iii: B _M =19 bits", "M2-iii: B _M =152 bits", and "M3-iii: B _M =380 bits" Each of the graphs shown as " represents a normalized beamforming gain of the Kronecker product mono codebook proposed in an embodiment of the present invention.

In particular, the performance graphs shown in FIG. 13 show that d _V in the communication system = 0.8λ, and performance graphs for d _h = 0.5λ are shown.

Also, in FIG. 13 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 13 , the normalized beamforming gains of the Kronecker product double codebooks proposed in an embodiment of the present invention are normalized beamforming gains of the Kronecker product mono codebooks proposed in an embodiment of the present invention. It can be seen that the better

In particular, it can be seen that the Kronecker product mono codebooks proposed in an embodiment of the present invention can reduce overall feedback overhead by sharing a wideband PMI among narrow RBs.

In FIG. 13, an example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention has been described. Another example of the normalized beamforming gain for the Kronecker product mono codebook and the normalized beamforming gain for the Kronecker product double codebook in the communication system according to an embodiment of the present invention will be described with reference to 14.

14 is a diagram schematically illustrating another example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention.

14, first, "D1-I: B _D =83 bits", "D2-I: B _D =102 bits", "D3-I: B _D =136 bits", and "D1-II : B _D =65 bits", "D2-II: B _D =90 bits", and "D3-II: B _D = 120 bits" are each of the graphs proposed in an embodiment of the present invention. Represents the normalized beamforming gain of the Kronecker product double codebook, "M1-iii: B _M =19 bits", "M2-iii: B _M =152 bits", and "M3-iii: B _M =380 bits" Each of the graphs shown as " represents a normalized beamforming gain of the Kronecker product mono codebook proposed in an embodiment of the present invention.

In particular, the performance graphs shown in FIG. 14 show that d _V in the communication system = 1.6λ, and performance graphs for d _h = 1.0λ are shown.

Also, in FIG. 14 , the vertical axis represents the normalized beamforming gain, and the horizontal axis represents the number of transmit antennas.

As shown in FIG. 14 , the normalized beamforming gains of the Kronecker product double codebooks proposed in an embodiment of the present invention are normalized beamforming gains of the Kronecker product mono codebooks proposed in an embodiment of the present invention. It can be seen that the better

In particular, it can be seen that the Kronecker product mono codebooks proposed in an embodiment of the present invention can reduce overall feedback overhead by sharing a wideband PMI among narrow RBs.

In FIG. 14, another example of a normalized beamforming gain for a Kronecker product mono codebook and a normalized beamforming gain for a Kronecker product double codebook in a communication system according to an embodiment of the present invention has been described. An internal structure of a signal transmission apparatus in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention will be described with reference to 15 .

15 is a diagram schematically illustrating an internal structure of a signal transmission apparatus in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 15 , the signal transmission apparatus 1500 may be, for example, a user terminal or a base station.

The signal transmission apparatus 1500 includes a transmitter 1511 , a controller 1513 , a receiver 1515 , and a storage unit 1517 .

First, the controller 1513 controls the overall operation of the signal transmission apparatus 1500, in particular related to the operation of performing a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention. An operation, in particular, an operation related to performing a beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention is controlled. An operation related to an operation of performing a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention according to an embodiment of the present invention, particularly the FD-MIMO scheme according to an embodiment of the present invention The operation related to the operation of performing the beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting do.

The transmitter 1511 transmits various signals and various messages to other entities under the control of the controller 1513, for example, to other entities such as a signal receiving device. Here, since the various signals and various messages transmitted by the transmitter 1511 are the same as those described with reference to FIGS. 2 to 14 , a detailed description thereof will be omitted herein.

Also, the receiver 1515 receives various signals and various messages from the other entities under the control of the controller 1513 . Here, since the various signals and various messages received by the receiver 1515 are the same as those described with reference to FIGS. 2 to 14 , a detailed description thereof will be omitted herein.

The storage unit 1517 performs a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention, which is performed by the signal transmission apparatus 1500 under the control of the controller 1513 . operation related to the operation, particularly the operation of performing the beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention; It stores related programs and various data.

In addition, the storage unit 1517 stores various signals and various messages received by the receiver 1515 from the other entities.

Meanwhile, FIG. 15 shows a case in which the signal transmission apparatus 1500 is implemented as separate units such as the transmitter 1511 , the controller 1513 , the receiver 1515 , and the storage unit 1517 . However, the signal transmission apparatus 1500 may be implemented in an integrated form of at least two of the transmitter 1511 , the controller 1513 , the receiver 1515 , and the storage unit 1517 .

Also, it goes without saying that the signal transmission apparatus 1500 may be implemented with one processor.

In FIG. 15, the internal structure of a signal transmission apparatus in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention has been described. Next, with reference to FIG. 16, FD-MIMO according to an embodiment of the present invention is described. An internal structure of a signal receiving apparatus in a communication system supporting the method will be described.

16 is a diagram schematically illustrating an internal structure of a signal receiving apparatus in a communication system supporting an FD-MIMO scheme according to an embodiment of the present invention.

Referring to FIG. 16 , the signal receiving apparatus 1600 may be, for example, a user terminal or a base station.

The signal receiving apparatus 1600 includes a transmitter 1611 , a controller 1613 , a receiver 1615 , and a storage unit 1617 .

First, the controller 1613 controls the overall operation of the signal receiving apparatus 1600, particularly related to the operation of performing a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention. An operation, in particular, an operation related to performing a beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention is controlled. An operation related to an operation of performing a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention according to an embodiment of the present invention, particularly the FD-MIMO scheme according to an embodiment of the present invention The operation related to the operation of performing the beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting do.

The transmitter 1611 transmits various signals and various messages to other entities under the control of the controller 1613, for example, to other entities such as a signal transmission device. Here, since the various signals and various messages transmitted by the transmitter 1611 are the same as those described with reference to FIGS. 2 to 14 , a detailed description thereof will be omitted herein.

Also, the receiver 1615 receives various signals and various messages from the other entities under the control of the controller 1613 . Here, since the various signals and various messages received by the receiver 1615 are the same as those described with reference to FIGS. 2 to 14 , a detailed description thereof will be omitted.

The storage unit 1617 performs a beamforming operation in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention, which is performed by the signal receiving apparatus 1600 under the control of the controller 1613 . operation related to the operation, particularly the operation of performing the beamforming operation based on the Kronecker product mono codebook and the Kronecker product double codebook in a communication system supporting the FD-MIMO scheme according to an embodiment of the present invention; It stores related programs and various data.

In addition, the storage unit 1617 stores various signals and various messages received by the receiver 1615 from the other entities.

Meanwhile, FIG. 16 shows a case in which the signal receiving apparatus 1600 is implemented as separate units such as the transmitter 1611 , the controller 1613 , the receiver 1615 , and the storage unit 1617 . However, the signal receiving apparatus 1600 may be implemented in an integrated form of at least two of the transmitter 1611 , the controller 1613 , the receiver 1615 , and the storage unit 1617 .

Also, it goes without saying that the signal receiving apparatus 1600 may be implemented with one processor.

Certain aspects of the present invention may also be embodied as computer readable code on a computer readable recording medium. A computer readable recording medium is any data storage device capable of storing data that can be read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, and , floppy disks, optical data storage devices, and carrier waves (such as data transmission over the Internet). The computer readable recording medium may also be distributed over network-connected computer systems, so that the computer readable code is stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for achieving the present invention can be easily interpreted by programmers skilled in the field to which the present invention is applied.

In addition, it will be appreciated that the apparatus and method according to an embodiment of the present invention can be realized in the form of hardware, software, or a combination of hardware and software. Any such software, for example, whether erasable or rewritable, may contain a volatile or non-volatile storage device such as a ROM, or a memory such as, for example, RAM, a memory chip, device or integrated circuit. , or an optically or magnetically recordable storage medium such as a CD, DVD, magnetic disk, or magnetic tape, for example, and a machine (eg, computer) readable storage medium. The method according to an embodiment of the present invention may be implemented by a computer or portable terminal including a control unit and a memory, wherein the memory is suitable for storing a program or programs including instructions for implementing embodiments of the present invention You will see that it is an example of a machine-readable storage medium.

Accordingly, the present invention includes a program including code for implementing the apparatus or method described in any claim of the present specification, and a machine (computer, etc.) readable storage medium storing such a program. Also, such a program may be transmitted electronically over any medium, such as a communication signal transmitted over a wired or wireless connection, and the present invention suitably includes the equivalent thereof.

In addition, the device according to an embodiment of the present invention may receive and store the program from a program providing device connected by wire or wirelessly. The program providing device may include a program including instructions for causing the program processing device to perform a preset content protection method, a memory for storing information necessary for the content protection method, and wired or wireless communication with the graphic processing device. It may include a communication unit for performing, and a control unit for automatically transmitting the program to the transceiver at a request of the graphic processing device or automatically.

Meanwhile, although specific embodiments have been described in the detailed description of the present invention, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.

Claims (22)

A method of performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, the method comprising:
identifying a rough beam of a first dominant beam;
identifying at least two codeword candidates based on the coarse beam of the first dominant beam;
and selecting one of the at least two codeword candidates as a final codeword.
According to claim 1,
The process of identifying at least two codeword candidates based on the coarse beam of the first dominant beam;
identifying a first codeword candidate among the at least two codeword candidates based on a scenario in which one dominant beam is assumed in a channel;
and identifying a second codeword candidate among the at least two codeword candidates based on a scenario assuming two dominant beams in a channel.
3. The method of claim 2,
identifying a second codeword candidate among the at least two codeword candidates based on a scenario in which two dominant beams are assumed in a channel;
The method comprising: identifying a second dominant beam and jointly combining with a first dominant beam corresponding to the first codeword candidate to identify the second codeword candidate.
According to claim 1,
The process of identifying a rough beam of the first dominant beam includes;
The method comprising identifying a Kronecker product of discrete Fourier transform (DFT) vectors as a coarse beam of the first dominant beam.
A method of performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, the method comprising:
identifying at least two beams for each of at least two first resource blocks (RBs);
identifying at least two codeword candidates for each of the second RBs based on the identified at least two beams;
and selecting one of the at least two codeword candidates as a final codeword.
6. The method of claim 5,
identifying at least two beams for each of the at least two first RBs;
and identifying a first dominant beam and a second dominant beam for each of the at least two first RBs.
7. The method of claim 6,
A wideband including a plurality of tones includes the at least two first RBs,
The method wherein each of the at least two first RBs includes at least two second RBs.
8. The method of claim 7,
Each of the at least two first RBs corresponds to a wideband precoding matrix indicator (PMI),
wherein each of the at least two second RBs corresponds to a narrowband PMI.
6. The method of claim 5,
identifying at least two codeword candidates for each of the second RBs based on the identified at least two beams;
identifying a first codeword candidate among the at least two codeword candidates based on a scenario in which one dominant beam is assumed in a channel;
and identifying a second codeword candidate among the at least two codeword candidates based on a scenario assuming two dominant beams in a channel.
10. The method of claim 9,
identifying a second codeword candidate among the at least two codeword candidates based on a scenario in which two dominant beams are assumed in a channel;
The method comprising: identifying a second dominant beam and jointly combining with a first dominant beam corresponding to the first codeword candidate to identify the second codeword candidate.
An apparatus for performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, the apparatus comprising:
Memory;
a processor coupled to the memory;
The processor is:
identifying a rough beam of a first dominant beam; identifying at least two codeword candidates based on a coarse beam of the first dominant beam; and selecting one as a final codeword.
12. The method of claim 11,
identifying at least two codeword candidates based on the coarse beam of the first dominant beam;
identifying a first codeword candidate among the at least two codeword candidates based on a scenario in which one dominant beam is assumed in a channel;
and identifying a second codeword candidate among the at least two codeword candidates in consideration of a scenario assuming two dominant beams in a channel.
13. The method of claim 12,
identifying a second codeword candidate among the at least two codeword candidates based on a scenario assuming two dominant beams in a channel;
and identifying a second dominant beam and jointly combining with a first dominant beam corresponding to the first codeword candidate to identify the second codeword candidate.
12. The method of claim 11,
Identifying a coarse beam of the first dominant beam includes;
and identifying a Kronecker product of discrete Fourier transform (DFT) vectors as a coarse beam of the first dominant beam.
An apparatus for performing a beamforming operation in a communication system supporting a frequency division-multiple input multiple output (FD-MIMO) scheme, the apparatus comprising:
Memory;
a processor coupled to the memory;
The processor is:
identifying at least two beams for each of at least two first resource blocks (RBs), and at least two codeword candidates for each of second RBs based on the identified at least two beams and identifying one of the at least two codeword candidates as a final codeword.
16. The method of claim 15,
identifying at least two beams for each of the at least two first RBs;
and identifying a first dominant beam and a second dominant beam for each of the at least two first RBs.
17. The method of claim 16,
A wideband including a plurality of tones includes the at least two first RBs,
wherein each of the at least two first RBs includes at least two second RBs.
18. The method of claim 17,
Each of the at least two first RBs corresponds to a wideband precoding matrix indicator (PMI),
each of the at least two second RBs corresponds to a narrowband PMI.
16. The method of claim 15,
identifying at least two codeword candidates for each of the second RBs based on the identified at least two beams;
identifying a first codeword candidate among the at least two codeword candidates based on a scenario in which one dominant beam is assumed in a channel;
and identifying a second codeword candidate among the at least two codeword candidates based on a scenario assuming two dominant beams in a channel.
20. The method of claim 19,
identifying a second codeword candidate among the at least two codeword candidates based on a scenario in which two dominant beams are assumed in a channel;
and identifying a second dominant beam and jointly combining with a first dominant beam corresponding to the first codeword candidate to identify the second codeword candidate. delete delete

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