KR102410283B1 - Method and apparatus for transmitting signal using multiple radio unit - Google Patents

Abstract

Determining an RU set including at least two RUs from among a plurality of RUs based on feedback received from the UE regarding the reception strength of a transmission beam formed by the plurality of RUs, information about the RUs included in the RU set determining a distributed precoding matrix corresponding to a diversity order of a predetermined size based on the distributed precoding matrix, and performing precoding based on the distributed precoding matrix and transmitting the precoded signal to the UE through the RU set A base station for transmitting a signal to a UE and a method for transmitting a signal are provided.

Description

Signal transmission method and apparatus using a plurality of RUs {METHOD AND APPARATUS FOR TRANSMITTING SIGNAL USING MULTIPLE RADIO UNIT}

The present disclosure relates to a method and apparatus for transmitting a signal using a plurality of RUs.

In a beamforming communication system using a distributed array antenna, most communication is performed along a line of sight (LoS). A millimeter wave with a short frequency wavelength is mainly used, and the array antenna uses beamforming technology to maximize power efficiency.

A multi-user wireless system using an unlicensed band limits the transmission power of a wireless signal in order to reduce interference to other devices. This is called a wireless power limited system (power limited system). On the other hand, since the system capacity of a multi-user wireless system using a licensed band is determined according to the number of frequency bands, it is called a radio band limited system. Therefore, in the design of a system using a licensed band, increasing the frequency efficiency is the most important goal.

One embodiment provides a method for transmitting a signal to a UE using a plurality of RUs.

Another embodiment provides a base station for transmitting a signal to a UE using a plurality of RUs.

According to one embodiment, a method is provided for a base station to transmit a signal to a user equipment (UE) using a plurality of radio units (RUs). The signal transmission method includes: determining an RU set including at least two RUs among a plurality of RUs based on a feedback regarding a reception strength of a transmission beam formed by the plurality of RUs, received from the UE, included in the RU set Determining a distributed precoding matrix corresponding to a diversity order of a predetermined size based on the information about the RU, and performing precoding based on the distributed precoding matrix and transmitting the precoded signal to the UE through the RU set sending it to

In the signal transmission method, the determining of the RU set includes grouping at least two RUs that have transmitted a beam corresponding to the feedback, and determining the RU set based on a channel matrix between the grouped at least two RUs and the UE. may include steps.

The determining of the RU set based on the channel matrix in the signal transmission method may include determining the RU set in which a ratio of singular values of the channel matrix is closest to 1.

The determining of the RU set based on the channel matrix in the signal transmission method may further include excluding from the determination an RU set having a difference of 0 between direction indication cosines corresponding to at least two RUs.

The determining of the RU set based on the channel matrix in the signal transmission method may further include excluding the RU set in which the determinant of the channel matrix is 0 from the determination.

The step of determining the RU set based on the channel matrix in the signal transmission method includes: a difference between direction indication cosines corresponding to at least two RUs among m RU sets in which a ratio of singular values of the channel matrix is close to 1 determining a non-zero RU set.

The step of determining the RU set based on the channel matrix in the signal transmission method includes: a ratio of singular values of the channel matrix among m sets of RUs in which a difference between direction indication cosines corresponding to at least two RUs is not 0 determining the RU set closest to this one.

In the signal transmission method, the determining of the RU set based on the channel matrix may include determining the RU set from among the RU sets in which a difference between direction indication cosines corresponding to at least two RUs is not 0.

In the signal transmission method, the determining of the RU set based on the channel matrix may include determining the RU set from among the RU sets in which the determinant of the channel matrix is not 0.

In the signal transmission method, the feedback may include an identifier of a transmission beam and an identifier of an RU that formed the transmission beam.

According to another embodiment, there is provided a base station that transmits a signal to a user equipment (UE) using a plurality of radio units (RUs). The base station includes a processor, a memory, and a radio frequency unit (RF unit), the processor executes a program stored in the memory, received from the UE, the reception strength of the transmission beam formed by the plurality of RUs determining a RU set including at least two RUs from among a plurality of RUs based on the feedback; determining a distributed precoding matrix corresponding to a diversity order of a predetermined size based on information about the RUs included in the RU set and performing precoding based on the distributed precoding matrix and transmitting the precoded signal to the UE through the RU set.

When the processor in the base station performs the step of determining the RU set, the step of grouping at least two RUs that have transmitted the beam corresponding to the feedback, and the RU set based on a channel matrix between the grouped at least two RUs and the UE can be performed to determine

In the base station, when the processor performs the step of determining the RU set based on the channel matrix, the step of determining the RU set in which the ratio of singular values of the channel matrix is closest to 1 may be performed.

When the processor in the base station performs the step of determining the RU set based on the channel matrix, the step of excluding the RU set in which the difference between the direction indication cosines corresponding to at least two RUs is 0 from the determination may be further performed. .

When the processor in the base station performs the step of determining the RU set based on the channel matrix, the step of excluding the RU set in which the determinant of the channel matrix is 0 may be further performed.

When the processor in the base station performs the step of determining the RU set based on the channel matrix, a direction indication corresponding to at least two RUs among the m RU sets in which the ratio of singular values of the channel matrix is close to 1 The step of determining the RU set in which the difference between cosines is not 0 may be performed.

When the processor in the base station performs the step of determining the RU set based on the channel matrix, a singular value of the channel matrix among m sets of RUs in which the difference between the direction indication cosines corresponding to at least two RUs is not 0 ) may perform the step of determining the RU set closest to 1.

In the base station, when the processor performs the step of determining the RU set based on the channel matrix, the step of determining the RU set from among the RU sets in which the difference between the direction indication cosines corresponding to at least two RUs is not 0 may be performed. have.

When the processor in the base station performs the step of determining the RU set based on the channel matrix, the processor may perform the step of determining the RU set from among the RU sets in which the determinant of the channel matrix is not 0.

The feedback from the base station may include the identifier of the transmit beam and the identifier of the RU that formed the transmit beam.

Based on precoding in a LoS environment using a short-wavelength carrier such as a millimeter wave, a signal capable of maximizing frequency efficiency and obtaining a diversity gain may be transmitted.

및

에 대한

을 나타낸 그래프이다.
도 4는 한 실시예에 따른 두 개의 클러스터 바운스가 존재하는 빔형성 송수신 시스템을 개략적으로 나타낸 개념도이다.
도 5는 두 개의 클러스터 바운스가 존재하는 빔형성 송수신 시스템의 무선 채널 매트릭스의 각도 영역 응답을 나타낸 그래프이다.
도 6은 한 실시예에 따른 네 개의 클러스터 바운스가 존재하는 빔형성 송수신 시스템을 개략적으로 나타낸 개념도이다.
도 7은 네 개의 클러스터 바운스가 존재하는 빔형성 송수신 시스템의 무선 채널 매트릭스의 각도 영역 응답을 나타낸 그래프이다.
도 8은 한 실시예에 따른 기지국 및 UE를 포함하는 무선 통신 시스템을 나타낸 블록도이다.
도 9는 한 실시예에 따른 기지국의 신호 송신 방법을 나타낸 흐름도이다.
도 10 및 도 11은 한 실시예에 따른 분산 프리코딩 매트릭스의 효과를 나타내는 개념도이다.
도 12는 다른 실시예에 따른 무선 통신 시스템을 나타낸 블록도이다.1 is a conceptual diagram illustrating a distributed array antenna system according to an embodiment.
2 is a schematic diagram of a wireless communication system according to an embodiment;
3 shows some

and

for

is a graph showing
4 is a conceptual diagram schematically illustrating a beamforming transmission/reception system having two cluster bounces according to an embodiment.
5 is a graph illustrating an angular domain response of a radio channel matrix of a beamforming transmission/reception system in which two cluster bounces exist.
6 is a conceptual diagram schematically illustrating a beamforming transmission/reception system having four cluster bounces according to an embodiment.
7 is a graph illustrating an angular domain response of a radio channel matrix of a beamforming transmission/reception system in which four cluster bounces exist.
8 is a block diagram illustrating a wireless communication system including a base station and a UE according to an embodiment.
9 is a flowchart illustrating a signal transmission method of a base station according to an embodiment.
10 and 11 are conceptual diagrams illustrating an effect of a distributed precoding matrix according to an embodiment.
12 is a block diagram illustrating a wireless communication system according to another embodiment.

Hereinafter, with reference to the accompanying drawings, it will be described in detail for those of ordinary skill in the art to which the present invention pertains to easily implement the embodiments of the present invention. However, the present description may be implemented in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the description in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, user equipment (UE) is a terminal, a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station (high reliability mobile station, HR-MS), subscriber station (subscriber station, SS), portable subscriber station (PSS), access terminal (AT), machine type communication device (machine type communication device, MTC device) and the like, and may include all or some functions of MT, MS, AMS, HR-MS, SS, PSS, AT, UE, and the like.

In addition, the base station (base station, BS) is an advanced base station (advanced base station, ABS), a high reliability base station (high reliability base station, HR-BS), a Node B (node B), an advanced node B (evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR)-BS, a relay serving as a base station station (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, high reliability relay station (HR) serving as a base station -RS), small base station [femto base station (femto BS), home node B (home node B, HNB), home eNodeB (HeNB), pico base station (pico BS), macro base station (macro BS), micro base station (micro BS) ), etc.], etc., may include all or some functions of ABS, NodeB, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR-RS, small base station, etc. have.

1 is a conceptual diagram illustrating a distributed array antenna system according to an embodiment.

Referring to FIG. 1 , a distributed array antenna environment is configured by a distributed base station radio unit (RU) (or BS-RU). The base station includes a digital unit (DU), and the RU is located at the same location as the DU (collocated) or is wired and distributed with the DU. The RU is also referred to as a remote radio head (RRH). Beamforming transmission/reception is performed between the RU and user equipment (UE).

Since the beamforming technique spatially collects and uses transmit/receive power, power efficiency may be increased. However, the beamforming technique cannot increase frequency efficiency (ie, system capacity) or increase diversity gain in a LoS channel environment. In a multipath channel other than the LoS channel environment, if certain conditions such as a difference in correlation between two path signals are satisfied, an additional spatial dimension is provided to the wireless communication system, and frequency efficiency and diver City gains can be increased. Accordingly, two or more RUs may communicate with one UE in order to minimize interference, maximize diversity gain, and increase radio resource use efficiency or frequency efficiency in communication between RUs and UEs. For example, if two RUs communicate with one UE, the rank of the radio channel matrix becomes 2. In addition, a separate condition is required to increase frequency efficiency and diversity gain. When the ratio between the eigen values of the channel matrix of a radio channel is defined as a condition number (CN) value, if the CN value is much greater than 1, the Degree of Freedom (DoF) gain does not increase. does not In addition, if the frequency efficiency is increased through the DoF gain, it is difficult to additionally obtain a diversity gain because the frequency efficiency is increased from the condition of the channel.

2 is a schematic diagram of a wireless communication system according to an embodiment;

)을 UE-RU에게 송신하고, 제2 RU는 제2 빔(

)을 UE-RU에게 송신한다. UE-RU와 RU 간의 거리는 L이고, RU의 높이는 H이다. Referring to FIG. 2 , beamforming transmission is being performed from two RUs (a first RU and a second RU) to a UE-RU included in a mobile body. The first RU is the first beam (

) to the UE-RU, and the second RU transmits the second beam (

) to the UE-RU. The distance between the UE-RU and the RU is L, and the height of the RU is H.

Hereinafter, the present description assumes that the array antenna is a Uniform Linear Array Antenna (ULA) and describes the equation of the array antenna with respect to the ULA. The present description may also be applied to any other type of array antenna such as a Circular Linear Array Antenna (CLA) or a Rectangular Plannar Array Antenna (RPA), in which case the expression of the equation described below This may vary slightly, but the present disclosure is not limited thereto.

이다.

는 방향 지시 코사인(directional cosine)이라고 한다.

또한 수신단의 ULA의 요소 안테나의 배열 방향과 송신단의 ULA에서 생성된 빔에 의해 형성된 각도로서 정의될 수 있다.Therefore, the angle formed by the second beam of the second RU with the horizontal direction (the direction in which the element antennas of the array antenna of the UE are arranged) is

to be.

is called the directional cosine.

In addition, it may be defined as an angle formed by the arrangement direction of the element antenna of the ULA of the receiving end and the beam generated by the ULA of the transmitting end.

Assuming that the transmission signal vector is x and the channel matrix is h , the reception signal vector y is expressed by Equation 1 below.

In Equation 1, w is a white noise vector. The channel matrix H is expressed as in Equation 2 below.

In Equation 2, h ₁ represents a channel between RU ₁ and the UE, and h ₂ represents a channel between RU ₂ and the UE. One row vector ( h ₁ ) of the channel matrix between the two RUs and the UE-RU in FIG. 2 . or h ₂ ) is expressed as in Equation 3 below.

는 캐리어 주파수의 파장,

는 캐리어 주파수의 파장을 단위로 정규화된, 수신단의 요소 안테나 간 거리(간격)이고,

은 UE-RU의 수신 배열 안테나의 개수이다. 수신단의 배열 안테나의 크기는 송신단과 수신단 사이의 거리에 비해 무척 작은 것으로 가정된다. 각 변수의 아래첨자 r 은 수신단(reception end)을 나타낸다.In Equation 3, a is path attenuation, which is a path attenuation value from an antenna element of the array antenna to a reception point. Path attenuation is assumed to be the same for all element antennas. d is the distance from the first element antenna to the receiving point,

is the wavelength of the carrier frequency,

is the distance (interval) between the element antennas of the receiving end, normalized by the wavelength of the carrier frequency,

is the number of receiving array antennas of the UE-RU. It is assumed that the size of the array antenna of the receiving end is very small compared to the distance between the transmitting end and the receiving end. The subscript r of each variable represents the reception end.

에 대한 함수

로 표시하면 아래 수학식 4와 같다.The vector part of Equation 3

function for

It is expressed as Equation 4 below.

는 방향 지시 코사인

에 대한 단위 공간 시그니처(the unit spatial signature)이다. function

is the direction indicating cosine

is the unit spatial signature for .

방향(즉, 신호 방향(signal direction))으로 투사(project)할 수 있는 수신기이다.An optimal receiver according to an embodiment transmits a noisy received signal of a channel h

A receiver capable of projecting in a direction (ie, a signal direction).

The channel gain h _k for each path according to Equations 2 to 4 is the same as Equation 5.

는 k번째 전송 안테나에서 수신 지점인 첫 번째 요소 안테나까지의 거리이다. 수학식 5에서 h _k 는 신호 방향(the signal direction) 또는 공간 시그니처(the spatial signature)라고 한다. 여기서 단위 공간 시그니처 함수

의 주기는

이다. 아래 수학식 6의 조건이 만족되면, 수학식 2의 채널 매트릭스 H 는 선형독립인 행을 갖는다.in Equation 5

is the distance from the k -th transmit antenna to the first element antenna, which is the reception point. In Equation 5, h _k is referred to as the signal direction or the spatial signature. where the unit space signature function

the cycle of

to be. When the condition of Equation 6 below is satisfied, the channel matrix H of Equation 2 has linearly independent rows.

및

(고유값(eigen value)의 제곱수)를 갖고, 풀 랭크(full rank)가 된다. 하지만, 채널 매트릭스 H 가 풀 랭크이더라도, 채널 매트릭스 H 의 자유도(degree of freedom, DoF)가 2가 아니라면 스펙트럼 효율성이 증가하지 않을 수 있다. When Equation 6 is satisfied, the channel matrix H is two non-zero singular values

and

(the number of squares of the eigen value), and full rank. However, even if the channel matrix H is full rank, the spectral efficiency may not increase unless the degree of freedom (DoF) of the channel matrix H is not two.

That is, even if the channel matrix is full rank, if a difference occurs in the size distribution of singular values, the DoF cannot be 2. When a difference occurs in the size distribution of singular values of the channel matrix, it is called an ill-condition. The variable to measure the low-level condition can be derived as follows.

및

의 사이의 각도

는 두 개의 벡터의 내적에 의해 아래 수학식 7과 같이 표현될 수 있다.The two spatial signatures of Figure 2

and

angle between

can be expressed as in Equation 7 below by the dot product of two vectors.

는

에 의해 결정될 수 있고, 수학식 7은 아래 수학식 8과 같이 정리된다.here

Is

can be determined by , and Equation 7 is rearranged as Equation 8 below.

은 수학식 4를 통해

및

에 대한 함수로 표현될 수 있고, 도 3은 몇 가지

및

에 대한

을 나타낸 그래프이다.

은 파장으로 정규화된 전송 요소 안테나 간의 거리(간격)이고,

은 수신 배열 안테나의 개수이므로, 정규화된 선형 안테나의 총 길이는

이다. 한 실시예에 따르면, 기지국은 수학식 8의

이 1에 근사한 값인지를 판단하여 UE에게 데이터를 송신할 적어도 두 개의 RU가 주파수 효율을 최대화하기 위해 적합한 RU인지 여부를 결정할 수 있다.of Equation 8

is through Equation 4

and

can be expressed as a function for

and

for

is a graph showing

is the distance (spacing) between the transmitting element antennas normalized to the wavelength,

is the number of receiving array antennas, so the total length of the normalized linear antenna is

to be. According to one embodiment, the base station of Equation (8)

By determining whether this value is close to 1, it is possible to determine whether at least two RUs for transmitting data to the UE are suitable RUs for maximizing frequency efficiency.

Meanwhile, the square of the singular value of the channel matrix is expressed by Equation 9 below.

If the condition number (CN) is calculated using Equation 9, it is as Equation 10.

및

의 비율이 1에 가깝게 되어야 한다. 즉, 두 개의 영이 아닌 특이값은 주파수 효율의 증가를 위해서 서로 비슷한 값을 가져야 한다. 두 개의 특이값의 비율이 1에 가까운 상태(즉,

)를 고급 조건(well-condition)이라고 한다. 반대로,

일 때 수학식 10은 무한대가 되고 저급 조건이다. 도 3의 그래프에 기반하여, 몇 가지 예시로서 다양한

,

, 및

에서

인 채널의 시그니처 변수

의 값이 계산될 수 있다. 이때는 채널이 풀 랭크더라도 DoF는 2가 되지 못하고 1이 된다. 예를 들어, 배열 안테나의 요소 안테나 간 간격이

일 때, 저급 조건이 되고 DoF는 1이 된다.For a channel's DoF to be 2, two non-zero singular values

and

ratio should be close to 1. That is, two non-zero singular values must have similar values to increase frequency efficiency. A state in which the ratio of two singular values is close to 1 (i.e.,

) is called a well-condition. on the other way,

When , Equation 10 becomes infinity and is a low-level condition. Based on the graph of Fig. 3, as some examples, various

,

, and

at

In-channel signature variable

can be calculated. In this case, even if the channel is full rank, the DoF becomes 1 instead of 2. For example, if the spacing between element antennas of an array antenna is

When , it is a low-level condition and DoF becomes 1.

는 ULA의 전체 길이

과 밀접하게 관련된다.

를 회피하기 위해서 본 개시에서는 수학식 11과 같은 변수 관계를 설정한다.

은 BS-RU 및 UE 사이의 거리를 나타내는, 도 2의 L과 구분된다.On the other hand, the direction indicating cosine variable

is the total length of the ULA

is closely related to

In order to avoid , in the present disclosure, a variable relationship as in Equation 11 is set.

is distinguished from L in FIG. 2 , indicating the distance between the BS-RU and the UE.

는 송수신 빔의 분해능과 관련된다. 수학식 11의 물리적 의미는 다음과 같다.

이 커지면 두 개의 인접한 빔을 구분해내기 위한 분해능이 작아지므로 작은 차이가 분별될 수 있다. 즉,

이 어느 정도 크면,

이 조금 크더라도

이므로 DoF는 2가 될 수 있다. in Equation 11

is related to the resolution of the transmit/receive beam. The physical meaning of Equation 11 is as follows.

As this becomes large, the resolution for distinguishing two adjacent beams decreases, so that small differences can be discerned. in other words,

If this is large enough,

even if it's a little big

Therefore, the DoF can be 2.

Hereinafter, a method for maximizing a diversity gain while maximizing DoF (ie, maximizing frequency efficiency) will be described with reference to FIGS. 4 to 10 .

4 is a conceptual diagram schematically illustrating a beamforming transmission/reception system having two cluster bounces according to an embodiment, and FIG. 5 is an angular domain response of a radio channel matrix of a beamforming transmission/reception system having two cluster bounces. It is a graph.

In FIG. 4 , there are two beams seen from the transmitting side and the receiving side. The beam arrives at the receiving end after being bounced from cluster 1 and cluster 2, respectively. Referring to FIG. 5 , the angular domain response of the radio channel matrix has two peaks, and thus the diversity order is 2.

6 is a conceptual diagram schematically illustrating a beamforming transmission/reception system having four cluster bounces according to an embodiment, and FIG. 7 is a diagram illustrating an angular domain response of a radio channel matrix of a beamforming transmission/reception system having four cluster bounces. It is a graph.

In FIG. 6, two beams are seen from the transmitting side and the receiving side, respectively. However, since each beam is reflected twice by the cluster on the radio channel, the number of paths for all beams is 4. Referring to FIG. 7 , the angular domain response of the radio channel matrix has four peaks, and thus the diversity order is 4. According to an embodiment, the base station may generate a distributed precoding matrix by modeling a cluster that reflects a beam. The base station performs precoding on data symbols to be transmitted to the UE using a distributed precoding matrix, and the UE receiving the precoded data symbols may obtain a diversity gain.

8 is a block diagram illustrating a wireless communication system including a base station and a UE according to an embodiment, FIG. 9 is a flowchart illustrating a signal transmission method of a base station according to an embodiment, and FIGS. 10 and 11 are one embodiment It is a conceptual diagram showing the effect of the distributed precoding matrix according to

Referring to FIG. 8 , a base station (or base station DU) 100 according to an embodiment includes a mapper 110 , a beamformer 120 , a precoding unit 130 , and a digital-to-analog converter (Digital to Analog, D). /A) 140 , and a control unit 150 . The base station 100 is connected to a plurality of RUs 200 through a wired link (Radio of Fiber, RoF). In the present description, the base station 100 may include a base station DU and an RU 200 , and the function of the base station DU may be described as a function of the base station 100 .

The mapper 110 maps data d _D,1- d _D,N to be transmitted to the UE 300 to a signal x _D,1- x _D,K .

The beamformer 120 forms a transmission beam based on the channel estimation result.

The precoding unit 130 performs precoding on the transmission beam.

The D/A 140 converts a digital signal into an analog signal and transmits it to the plurality of RUs 200 through a link.

The controller 150 controls the mapper 110 , the beamforming unit 120 , the precoding unit 130 , and the D/A 140 . According to an embodiment, the controller 150 determines a distributed precoding matrix so that the precoding unit 130 can perform precoding on the transmission beam formed by the beamformer 120 . Hereinafter, a signal transmission method of the base station 100 will be described in detail with reference to FIGS. 9 to 11 .

Referring to FIG. 9 , the base station 100 receives feedback regarding a plurality of transmission beams transmitted through the plurality of RUs 200 from the UE 300 ( S110 ). According to an embodiment, each of the plurality of RUs 200 forms a transmit beam using a transmit array antenna, and the UE 300 measures the reception strength of the transmit beam. The UE 300 may measure a reception strength of a transmission beam and transmit feedback regarding some transmission beams to the base station 100 according to a predetermined criterion. The feedback may include the identifier of the transmit beam and the identifier of the RU that formed the transmit beam.

For example, the UE 300 may transmit all identifiers of the transmission beam measured with a size greater than a predetermined intensity to the base station 100 . That is, the UE 300 may transmit an identifier of a transmission beam having a reception power of P or more to the base station 100 . Alternatively, the UE 300 may transmit identifiers of a predetermined number of transmission beams to the base station 100 . For example, the UE 300 may transmit the identifiers of the n beams to the base station 100 in the order of the greatest measured reception strength. Alternatively, the UE 300 may transmit, to the base station 100 , an identifier of a transmission beam having the greatest intensity among the transmission beams of each RU. In this case, the number of identifiers of transmission beams included in the feedback may be equal to or greater than the number of RUs.

Thereafter, the base station 100 determines an RU set including at least two RUs for transmitting a signal to the UE 300 among the plurality of RUs 200 based on the feedback from the UE 300 ( S120 ). The base station 100 according to an embodiment groups at least two RUs that have transmitted a beam corresponding to the feedback of the UE 300 into an RU set, and determines an RU set capable of maximizing frequency efficiency among the grouped RU sets. do.

According to an embodiment, the base station 100 may determine an RU set capable of maximizing frequency efficiency based on a channel matrix between at least two RUs and a UE included in each grouped RU set. If the number of RUs that have transmitted a beam corresponding to the feedback of the UE 300 is s, the number of RU sets to be searched for when the base station 100 transmits a signal to the UE 300 using two RUs is _s C ₂ , when the base station 100 transmits a signal to the UE 300 using three RUs, the number of RU sets to search for is _s C ₃ . For example, if the number of RUs that have transmitted the transmission beam fed back by the UE 300 is 4, when the number of RUs to be included in the RU set is 2, the base station 100 sets 6 ( ₄ C ₂ ) RU sets. When the number of RUs to be included in the RU set is three, the base station 100 searches for four ( ₄ C ₃ ) sets of RUs.

The base station 100 may use Equations 6 and 10 when determining whether at least two RUs included in the RU set are suitable sets as RUs to transmit signals. If the number of RUs included in the RU set is 2, the channel matrix H of Equation 2 has two column vectors. If the number of RUs included in the RU set is n, the channel matrix H of Equation 2 has n column vectors.

및

로부터 계산될 수 있는

조건에 기반하여 채널 매트릭스가 풀 랭크인지 여부를 판단할 수 있다(도 2 참조). 기지국(100)은

(또는 채널 매트리스의 행렬식이 0(det( H )=0))인 RU 세트는 RU 세트의 결정에서 제외할 수 있다. Equation 6 is used when determining whether the channel matrix between the RU set and the UE is full rank. For example, the base station 100 is

and

can be calculated from

It may be determined whether the channel matrix is full rank based on the condition (see FIG. 2 ). The base station 100 is

(or the RU set in which the determinant of the channel matrix is 0(det( H )=0)) may be excluded from the determination of the RU set.

는 수신단 ULA의 요소 안테나의 배열 선(the line of the array)과 송신단 ULA에 의해 생성된 빔의 방향 사이의 각도로 정의된다. 아래에서는 이러한 변수의 값을 계산하는 한 가지 예시를 설명한다. 한 실시예에 따른 기지국(100)은 RU 세트의 RU와 UE(300) 간의 거리 및 RU의 높이(지상으로부터의 높이 H) 바탕으로 방향 지시 코사인

를 계산한다. 이후 기지국(100)은 방향 지시 코사인

를 이용하여

조건의 충족 여부를 판단할 수 있다. variable

is defined as the angle between the line of the array of the element antenna of the receiving end ULA and the direction of the beam generated by the transmitting end ULA. An example of calculating the values of these variables is described below. The base station 100 according to an embodiment is a direction indication cosine based on the distance between the RU and the UE 300 of the RU set and the height of the RU (height H from the ground)

to calculate Since the base station 100 is a direction indication cosine

using

It can be determined whether the conditions are satisfied.

및

의 비율이 1인지 여부에 따라 RU 세트와 UE 간 채널이 고급 조건인지 여부를 결정할 수 있다. 기지국(100)은 수학식 6 및 수학식 10의 조건을 조합하여 주파수 효율을 최대화할 수 있는 RU 세트를 결정할 수 있다. 예를 들어, 기지국(100)은 채널 매트릭스 H 의 특이값인

및

의 비율이 1에 가까운 m개의 RU 세트 중

을 만족하는 RU 세트(또는 채널 매트릭스의 행렬식이 0이 아닌 RU 세트)를 선택할 수 있다. 채널 매트릭스 H 의 특이값인

및

의 비율이 1에 가까운 m개의 RU 세트는 1에 가까운 순서대로 선택될 수 있다. 또는 기지국(100)은

을 만족하는 m개의 RU 세트(또는 채널 매트릭스의 행렬식이 0이 아닌 RU 세트) 중에서 채널 매트릭스 H 의 특이값인

및

의 비율이 1에 가장 가까운 RU 세트를 선택할 수 있다. RU 세트는 적어도 두 개의 RU를 포함한다. Equation 10 is used when determining whether the channel between the RU set and the UE is an advanced condition. The base station 100 is a singular value of the channel matrix H

and

It can be determined whether the channel between the RU set and the UE is an advanced condition according to whether the ratio of is 1 or not. The base station 100 may determine a set of RUs capable of maximizing frequency efficiency by combining the conditions of Equations (6) and (10). For example, the base station 100 is a singular value of the channel matrix H

and

Among the m sets of RUs where the ratio of

A set of RUs (or a set of RUs in which the determinant of the channel matrix is not 0) may be selected. The singular value of the channel matrix H is

and

A set of m RUs in which the ratio of is close to 1 may be selected in the order of being close to 1. Or the base station 100 is

The singular value of the channel matrix H among m sets of RUs (or sets of RUs in which the determinant of the channel matrix is not 0) satisfying

and

A set of RUs in which the ratio of is closest to 1 may be selected. The RU set includes at least two RUs.

Thereafter, the base station 100 determines a distributed precoding matrix having a predetermined diversity order (S130). Equation 12 shows that when there are two RUs 200 selected by the base station 100, the data symbol matrix X=[x ₁ x ₂ ] ^T to be transmitted to the UE 300 and the precoded signal S=[s ₁ s ₂ ] represents the relationship between ^T.

The base station 100 transmits the precoded signal to the UE 300 through the selected RU 200 using the distributed precoding matrix as in Equation 12 (S140). That is, the elements x ₁ and x ₂ of the data symbol X are precoded by the distributed precoding matrix C before being transmitted to the UE 300 through the layer 1 and the layer 2, respectively. Equation 13 below is an example of a distributed precoding matrix C having elements h _i,j ( i,j =1,2).

및

는 각 RU(200)의 UE(300)를 향한 빔이 UE(300)의 배열 안테나의 요소 안테나가 배열된 방향과 이루는 각도이다(도 2 참조). 한 실시예에 따르면, 기지국(100)은 RU(200)로부터 UE(300)로 향하는 송신 빔이 UE(300)의 배열 안테나의 요소 안테나가 배열된 방향과 이루는 각도에 기반하여 분산 프리코딩 매트릭스를 결정할 수 있다. 수학식 13의 분산 프리코딩 매트릭스는 다이버시티 오더 4에 대응하는 매트릭스이고, 기지국(100)은 미리 결정된 크기의 다이버시티 오더에 대응하는 분산 프리코딩 매트릭스를 결정할 수 있다. 분산 프리코딩 매트릭스는 표준 규격에 정의되어 있는 프리코딩 매트릭스 중 하나일 수 있다.From Equation 13

and

is an angle formed by the beam toward the UE 300 of each RU 200 with the direction in which the element antennas of the array antenna of the UE 300 are arranged (see FIG. 2 ). According to one embodiment, the base station 100 generates a distributed precoding matrix based on an angle formed by the transmission beam from the RU 200 to the UE 300 and the direction in which the element antennas of the array antenna of the UE 300 are arranged. can decide The distributed precoding matrix of Equation 13 is a matrix corresponding to diversity order 4, and the base station 100 may determine a distributed precoding matrix corresponding to a diversity order of a predetermined size. The distributed precoding matrix may be one of the precoding matrices defined in the standard specification.

Referring to FIG. 9 , the base station 100 uses a distributed precoding matrix corresponding to diversity order 2, and the UE 300 reflects the signals received from the two RUs 200 in cluster 1 of FIG. This allows us to interpret it as the same as the signal (120˚ to the ground) and the signal reflected from cluster 2 (-175˚ to the ground). That is, the signal of diversity order 2 may be transmitted to the UE 300 by the distributed precoding matrix. Alternatively, referring to FIG. 10 , the base station 100 uses a distributed precoding matrix corresponding to diversity order 4, and the UE 300 transmits signals received from two RUs 200 in cluster 1 of FIG. This allows us to interpret the reflected signal (60˚ to the ground) and the reflected signal from cluster 2 (-175˚ to the ground) as the same. That is, the signal of diversity order 4 may be transmitted to the UE 300 by the distributed precoding matrix.

12 is a block diagram illustrating a wireless communication system according to another embodiment.

Referring to FIG. 12 , a wireless communication system according to an embodiment includes a base station 1210 and a UE 1220 .

The base station 1210 includes a processor 1211 , a memory 1212 , and a radio frequency unit (RF unit) 1213 . The memory 1212 may be connected to the processor 1211 to store various information for driving the processor 1211 or at least one program executed by the processor 1211 . The wireless communication unit 1213 may be connected to the processor 1211 to transmit and receive wireless signals. The processor 1211 may implement the functions, processes, or methods proposed in the embodiments of the present disclosure. In this case, in the wireless communication system according to an embodiment of the present disclosure, the air interface protocol layer may be implemented by the processor 1211 . The operation of the base station 1210 according to an embodiment may be implemented by the processor 1211 .

The UE 1220 includes a processor 1221 , a memory 1222 , and a wireless communication unit 1223 . The memory 1222 may be connected to the processor 1221 to store various information for driving the processor 1221 or at least one program executed by the processor 1221 . The wireless communication unit 1223 may be connected to the processor 1221 to transmit and receive wireless signals. The processor 1221 may implement the functions, steps, or methods proposed in the embodiments of the present disclosure. In this case, in the wireless communication system according to an embodiment of the present disclosure, the air interface protocol layer may be implemented by the processor 1221 . The operation of the UE 1220 according to an embodiment may be implemented by the processor 1221 .

In the embodiment of the present disclosure, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various known means. The memory is various types of volatile or non-volatile storage media, and for example, the memory may include a read-only memory (ROM) or a random access memory (RAM).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the right.

Claims (20)

A method of transmitting a signal to a receiving device, comprising:
determining a RU set including at least two RUs based on a direction indicating cosine between at least two radio units and the receiving device and a spatial signature function having the direction indicating cosine as variables;
determining a distributed precoding matrix corresponding to a diversity order of a predetermined size based on information about RUs included in the RU set; and
performing precoding on the signal based on the distributed precoding matrix and transmitting the precoded signal to the receiving device through the RU set
including,
When the difference between the first direction indicating cosine and the second direction indicating cosine is non-zero and the inner product of the first spatial signature function and the second spatial signature function is a minimum value, the first one of the at least two RUs The RU set including the RU and the second RU is determined,
The first direction indication cosine is determined between the receiving device and the first RU, the second direction indication cosine is determined between the receiving device and the second RU, and the first spatial signature function is the first spatial signature function. The method of claim 1, wherein the direction indicating cosine is a variable and the second spatial signature function has the second direction indicating cosine as a variable. delete delete delete delete delete delete delete delete delete A transmitting device for transmitting a signal to a receiving device, comprising:
It includes a processor, a memory, and a radio frequency unit (RF unit), wherein the processor executes the program stored in the memory,
determining a RU set including at least two RUs based on a direction indicating cosine between at least two radio units and the receiving device and a spatial signature function having the direction indicating cosine as variables;
determining a distributed precoding matrix corresponding to a diversity order of a predetermined size based on information about RUs included in the RU set; and
performing precoding on the signal based on the distributed precoding matrix and transmitting the precoded signal to the receiving device through the RU set;
do,
When the difference between the first direction indicating cosine and the second direction indicating cosine is non-zero and the inner product of the first spatial signature function and the second spatial signature function is a minimum value, the first one of the at least two RUs The RU set including the RU and the second RU is determined,
The first direction indication cosine is determined between the receiving device and the first RU, the second direction indication cosine is determined between the receiving device and the second RU, and the first spatial signature function is the first spatial signature function. A transmitting apparatus, having a direction indicating cosine as a variable and the second spatial signature function having the second direction indicating cosine as a variable. delete delete delete delete delete delete delete delete delete

Images