KR20140089312A - Method for transmitting signal using multiple antennas - Google Patents

Abstract

Disclosed is a method for transmitting a signal using multiple antennas. A base station transmits a reference signal using a plurality of beams which are formed using respective multiple antenna groups; receives a first precoder matrix index (PMI-1) and a second precoder matrix index (PMI-2) corresponding to the reference signal from a terminal; and performs precoding of a downlink transmission signal based on a first precoder corresponding to the first precoder matrix index and a second precoder corresponding to the second precoder matrix index. Therefore, the present invention can increase the capacity of a system.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of transmitting signals using multiple antennas,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication technology, and more particularly, to a signal transmission method using multiple antennas capable of increasing the capacity of a wireless communication system.

Multiple antenna techniques or Multiple Input Multiple Output (MIMO) techniques have been used to increase the capacity of wireless communication systems. The multi-antenna technique uses a beamforming (BF) technique for obtaining array gain using correlation between antennas and a technique for obtaining a multiplexing gain using free space inertia between antennas Space Multiplexing (SM) technology.

The beam forming technique shapes the electromagnetic waves radiated from the transmitter antenna in a specific direction to provide a high signal-to-noise ratio (SNR) to the target receiver and less interference to other receivers.

Therefore, the mobile communication base station can provide a good quality communication service to the terminals located at the cell boundary by applying the beam forming technology, and the space division multiple access (SDMA) technology based on the beam forming is applied to the spatially separated terminals It is possible to simultaneously provide services to a plurality of terminals in the same spectrum.

On the other hand, a multiplexing gain can be obtained when correlation between a plurality of antennas is low. According to information theory, the capacity increase of the system by the multiplexing gain is larger than the capacity increase of the system by the beam formation.

To apply spatial multiplexing (SM), a high signal-to-noise ratio is required. Also, in order to obtain a large effect by applying the spatial multiplexing technique, the rank of the MIMO channel should be a sufficiently large value, but it is not. In this case, a sufficient rank can not be obtained. In a long distance without a line of sight (LOS), the rank value is sufficient, but the signal-to-noise ratio is low. That is, the environment in which the spatial multiplexing technique can be applied is limited.

According to information theory, the capacity increase due to multiplexing is better than the capacity increase due to array gain, but the environment in which the multiplexing gain should be pursued and the environment in which the array gain should be pursued are distinguished from each other. Thus, there are commercially available wireless communication systems pursuing multiplexing gain, and commercially available wireless systems pursuing array gain.

It is an object of the present invention to provide a signal transmission method using multiple antennas capable of increasing the capacity of a system.

According to another aspect of the present invention, there is provided a signal transmission method using multiple antennas in a base station, the method comprising: transmitting signals through a plurality of beams formed using a plurality of antenna groups, Receiving a first precoder matrix index (PMI-1) and a second precoder matrix index (PMI-2) corresponding to the reference signal from a terminal, and transmitting the first precoder matrix index And precoding the downlink transmission signal based on a first precoder corresponding to the index and a second precoder corresponding to the second precoder matrix index.

Here, each of the plurality of antenna groups includes a plurality of antennas arranged so as to be correlated with each other, and the plurality of antenna groups may be arranged so that there is no correlation between the antenna groups.

Here, the first precoder may be a precoder for forming a beam, each of the plurality of antenna groups may be a pre-coder for obtaining a multiplexing gain using a beam formed by each of the plurality of antenna groups, Lt; / RTI >

Here, the reference signal may be generated by mixing a PN (Pseudo-Noise) sequence and an OCC (Orthogonal Cover Code) sequence. The reference signal is transmitted using the same first precoder. A PN sequence may be used for intercell interference and inter-beam interference mitigation, and an OCC sequence may be used for beam division generated by each antenna group. Therefore, the type of the OCC sequence can be defined to be equal to the number of antenna groups. The PN sequence may be initialized in units of a predetermined time interval. As the initial value of the PN sequence, at least one of a cell delimiter, a beam delimiter, and an index of a preset time interval may be used.

The multi-antenna signal transmission method described above provides an antenna structure, a precoder design method, a reference signal design method, and a demodulation reference signal design method that can simultaneously obtain an array gain and a multiplexing gain.

The signal transmission method using multiple antennas according to the embodiment of the present invention can be applied to both data channel and control channel transmission and can also be used for improving the reception performance and mitigating interference between cells located in a cell boundary region .

In addition, according to the signal transmission method using multiple antennas, SU-MIMO that transmits data of a plurality of layers at the same time using the same spectrum to a specific terminal, as well as MU-MIMO method that simultaneously transmits data to a plurality of terminals in the same spectrum As shown in FIG.

Therefore, it is possible to dramatically increase the capacity of the system by increasing the capacity of the data and control channels, as well as improving intercell interference and improving cell boundary performance with the same antenna structure.

1 is a conceptual diagram for explaining a signal transmission method using an array antenna.
2 illustrates a multiple antenna structure according to an embodiment of the present invention.
3 illustrates a multiple antenna structure according to another embodiment of the present invention.
4 illustrates a multiple antenna structure according to another embodiment of the present invention.
5 and 6 are conceptual diagrams for explaining a beam forming method in a signal transmission method using multiple antennas according to an embodiment of the present invention.
7 is a conceptual diagram illustrating a signal transmission method using multiple antennas according to an embodiment of the present invention.
8 is a conceptual diagram for explaining a reference signal transmission method according to an embodiment of the present invention.
9 is a conceptual diagram for explaining a method of applying a signal transmission method using multiple antennas to a cell boundary region according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, 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 this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the present invention, the same reference numerals are used for the same constituent elements in the drawings and redundant explanations for the same constituent elements are omitted.

Embodiments of the present invention described below may be applied to standard documents disclosed in at least one of IEEE (Institute of Electrical and Electronics Engineers) 802 system, 3rd Generation Partnership Project (3GPP) system, 3GPP LTE system and 3GPP2 system . In other words, steps or portions of embodiments of the present invention which are not described in order to clearly illustrate the technical idea of the present invention can be supported by the above-mentioned standard documents. In addition, all terms used in the present invention can be described by the standard document.

The term 'terminal' used in the present application includes a mobile station (MS), a user equipment (UE), a machine type communication (MTC) device, a mobile terminal (MT) A wireless terminal, an access terminal (AT), a subscriber unit, a subscriber station (SS), a wireless device, a wireless communication device, a wireless transmit / receive unit (WTRU) Receive Unit), mobile node, mobile, or some other terminology.

The term 'base station' used in the present application is used to mean a control device for controlling one cell. However, in an actual wireless communication system, a physical base station can control a plurality of cells, in which case the physical base station can be regarded as including at least one base station used in the present application. For example, it should be understood that parameters assigned differently for each cell in the present application assign different values to each base station. The 'base station' includes a base station, a Node-B, an eNode-B, a BTS (Base Transceiver System), an access point, It can be called another term.

A method of transmitting signals using multiple antennas according to an embodiment of the present invention provides a precoder designing method and a reference signal designing method capable of simultaneously obtaining a multiplexing gain and an array gain. Also, the signal transmission method using multiple antennas according to the embodiment of the present invention can be applied not only to the data channel but also to the control channel transmission, and the capacity of the system can be dramatically increased.

1 is a conceptual diagram for explaining a signal transmission method using an array antenna.

)(103)는

행렬로 구성된다.

는 안테나 포트(antenna port) 수를 의미하고,

는 레이어(layer) 수를 의미한다.As shown in FIG. 1, the array antenna 101 includes antenna groups in which antennas are arranged at regular intervals. In Fig. 1, a precoder

) 103,

Matrix.

Denotes the number of antenna ports,

Means the number of layers.

)는 1이 된다. 또한, 이 경우 어레이 안테나(101)를 구성하는 안테나 포트 수는

이지만 어레이 안테나(101)는 하나의 안테나처럼 동작하게 된다.When the spacing between the individual antennas constituting the array antenna 101 is sufficiently narrow (for example, when the spacing between the antennas is spaced by a half wavelength) and the antennas are correlated with each other, An appropriate weight may be assigned to each of the individual antennas constituting the antenna 101 so that a beam directed in a desired direction can be formed. When a beam is formed using the array antenna 101, the number of layers (

) Becomes 1. In this case, the number of antenna ports constituting the array antenna 101 is

The array antenna 101 operates as one antenna.

개의 안테나 포트는 각각 개별적인 안테나로 동작한다. On the other hand, when the intervals between the individual antennas constituting the array antenna 101 are sufficiently wide and there is no correlation between the antennas, the array antenna 101 can not form a beam oriented in a specific direction. In this case, each antenna constituting the array antenna 101 transmits a signal in its own beam pattern,

Each of the antenna ports operates as a separate antenna.

When the antennas constituting the array antenna 101 are correlated with each other, the precoder 103 is associated with the actually formed beam pattern. However, in the case of the array antenna 101 composed of antennas not correlated with each other, the precoder 103 is not related to the beam pattern radiated in a specific direction. If the antennas are not correlated, the signals that are fed into the individual antenna via the precoder 103 designed for a specific purpose are radiated through a beam pattern peculiar to the individual antenna.

2 illustrates a multiple antenna structure according to an embodiment of the present invention. 3 illustrates a multiple antenna structure according to another embodiment of the present invention. 4 illustrates a multiple antenna structure according to another embodiment of the present invention.

Hereinafter, a multi-antenna structure and operation according to embodiments of the present invention will be described with reference to FIG. 2 to FIG.

Referring to FIGS. 2 to 4, the multiple antennas according to the embodiment of the present invention may include 16 antennas, and may be composed of 4 antenna groups. Each antenna group may include four antennas.

2, multiple antennas 200 according to an exemplary embodiment of the present invention may include antenna groups 0 to 3 (210 to 240), and antenna groups may be arranged to form one column .

The separation distance between each antenna group can be configured to be sufficiently long so that there is no correlation between the antenna groups. For example, the separation distance between each antenna group may be configured to be 4? (Where? Means a wavelength).

In addition, the separation distance between the antennas 211, 221, 231, and 241 included in each antenna group can be configured to be sufficiently close to ensure the correlation between the antennas. For example, the separation distance between the antennas included in each antenna group may be? / 2.

2, each of the antenna groups 210 to 240 can operate as one antenna, and thus, the multiple antennas 200 including 16 antennas can operate as four antennas can do.

Referring to FIG. 3, the multiple antennas 300 according to another embodiment of the present invention may include antenna groups 0 to 3 (310 to 340). Here, the antenna group 0 310 and the antenna group 1 320 may be configured to have different polarizations so that the antenna group 0 310 and the antenna group 1 320 are not correlated with each other Therefore, it is not necessary to have a sufficient separation distance. For example, as shown in FIG. 3, the individual antenna 311 included in the antenna group 0 310 and the individual antenna 321 included in the antenna group 1 320 may be disposed in an intersecting manner .

The antenna group 2 330 and the antenna group 3 340 may be configured to have different polarizations so that the antenna group 2 330 and the antenna group 3 340 do not have to be sufficiently spaced from each other.

Since the antenna group 1 310 and the antenna group 2 330 have the same polarization and the antenna group 1 320 and the antenna group 3 340 can have the same polarization, And the antenna group 1 320 and the antenna group 2 330 and the antenna group 3 340 may be configured to be distances sufficiently long such that there is no correlation between the antenna groups. For example, the separation distance between antenna groups 0 and 1 (310, 320) and antenna groups 2 and 3 (330, 340) may be configured to be 4?.

In addition, the separation distance between the antennas included in each antenna group can be configured to be sufficiently close to ensure the correlation between the antennas. For example, the separation distance between the antennas included in each antenna group may be? / 2.

3, each of the antenna groups 310 to 340 may operate as one antenna, so that the multiple antennas 300 including 16 antennas operate as four antennas can do.

Referring to FIG. 4, a multiple antenna 400 according to another embodiment of the present invention may be composed of antenna group 0 to antenna group 3 (410 to 440), and antenna groups are arranged to form one row .

The separation distance between each antenna group can be configured to be sufficiently long so that there is no correlation between the antenna groups. For example, the separation distance between each antenna group may be configured to be 4?.

In addition, the separation distance between the antennas included in each of the antenna groups 410, 420, 430, and 440 may be configured to be sufficiently close to ensure the correlation between the antennas. For example, the separation distance between the antennas included in each antenna group may be? / 2.

4, each of the antenna groups 410 to 440 can operate as one antenna, so that the multiple antennas 400 including 16 antennas can operate as four antennas can do.

In FIGS. 2 to 4, for convenience of description, a total of 16 multiple antennas are formed, and four antenna groups each including four antennas are shown as examples. However, the technical idea of the present invention is not limited to the number of antenna groups, the number of antennas, and the antenna structure of the multiple antennas shown in FIG. 2 to FIG. In other embodiments of the present invention, the total number of antennas, the number of antenna groups, the number of antennas included in each antenna group, the number of antennas or the number of antennas Or an antenna arrangement structure.

5 and 6 are conceptual diagrams for explaining a beam forming method in a signal transmission method using multiple antennas according to an embodiment of the present invention. FIGS. 5 and 6 illustrate a beam forming method using the multiple antenna 300 shown in FIG.

개의 고정 안테나 방사 패턴(또는 고정빔, fixed beam)을 형성할 수 있다. 또한, 기지국은 안테나 그룹 1(320)에 포함된 안테나들을 이용하여 전체 서비스 영역을 지원할 수 있는

개의 고정 안테나 방사 패턴을 형성할 수 있다. 또한, 기지국은 안테나 그룹 2(330)에 포함된 안테나들을 이용하여 전체 서비스 영역을 지원할 수 있는

개의 고정 안테나 방사 패턴을 형성할 수 있다. 또한, 기지국은 안테나 그룹 3(340)에 포함된 안테나들을 이용하여 전체 서비스 영역을 지원할 수 있는

개의 고정 안테나 방사 패턴을 형성할 수 있다.In the multi-antenna 300 structure shown in FIG. 3, the base station can support the entire service area using the antennas included in the antenna group 0 (310)

(Or a fixed beam) can be formed. In addition, the base station can use the antennas included in the antenna group 1 320 to support the entire service area

It is possible to form a number of fixed antenna radiation patterns. In addition, the base station can use the antennas included in the antenna group 2 330 to support the entire service area

It is possible to form a number of fixed antenna radiation patterns. In addition, the base station can use the antennas included in the antenna group 3 340 to support the entire service area

It is possible to form a number of fixed antenna radiation patterns.

개의 고정 안테나 방사 패턴을 형성할 수 있다.Although FIG. 5 illustrates a fixed antenna radiation pattern that can be formed by the multiple antenna 300 according to another embodiment of the present invention shown in FIG. 3, The antenna structure can also support the entire service area as shown in FIG. 5

It is possible to form a number of fixed antenna radiation patterns.

)를 16개로 예시하였으나 여기에 한정되는 것은 아니며, 전체 서비스 영역을 지원하기 위한 고정 안테나 방사 패턴의 수는 각 안테나 그룹을 구성하는 개별 안테나의 수 및/또는 각 안테나 그룹에 포함된 개별 안테나들의 고유 방사 패턴 등에 따라 달라질 수 있다.5, for convenience of description, the number of fixed antenna radiation patterns supporting the entire service area (

The number of fixed antenna radiation patterns for supporting the entire service area is determined by the number of individual antennas constituting each antenna group and / or the number of antennas included in each antenna group Radiation pattern, and the like.

개의 고정 안테나 방사 패턴 각각은 4개의 안테나 그룹이 각각 형성한 동일한 방향의 4개 빔이 중첩(overlap)된 것이다. 즉, 안테나 그룹 0 내지 안테나 그룹 3(310 내지 340) 각각은 도 5에 도시한 16개 방향으로 빔을 전송할 수 있으므로 도 5에 도시된 각 빔은 사실 4개의 동일 방향 빔이 중첩된 것이다.5

Each of the fixed antenna radiation patterns is formed by overlapping four beams in the same direction formed by the four antenna groups. That is, since each of the antenna group 0 to the antenna group 3 (310 to 340) can transmit the beam in the 16 directions shown in FIG. 5, each beam shown in FIG. 5 is actually a superposition of four identical direction beams.

FIG. 6 shows an example of a specific beam (beam 15) among the 16 beams shown in FIG.

As shown in FIG. 6, the beam 15 may be constructed by superimposing four fixed beams 601 to 604 formed by the antenna group 0 to the antenna group 3 (310 to 340). Each beam (beam 0 to beam 15) shown in FIG. 5 is formed by superimposing four fixed beams formed by the antenna groups 0 to 3 (310 to 340) in the corresponding beam direction, as shown in FIG. 6 .

As shown in FIGS. 5 and 6, signals transmitted through the four fixed antenna radiation patterns formed in a specific direction may arrive at the receiver via different paths. For example, as shown in FIG. 6, signals transmitted through four fixed antenna radiation patterns (or fixed beams) may arrive at the receiver via different radio channels or with different phases. In the present invention, as described above, each of the plurality of antenna groups forms a fixed beam in a specific direction, thereby obtaining an array gain, and fixed beams formed by a plurality of antenna groups in a specific direction are transmitted to the receiver Multiplexing gain can be achieved as it arrives.

That is, in the signal transmission method using multiple antennas according to the embodiment of the present invention, the array gain and the multiplexing gain can be simultaneously obtained by using the beam forming method using multiple antennas and multiple antennas as shown in FIGS. 2 to 6 .

Hereinafter, the precoder design method and the reference signal design method for obtaining the array gain and the multiplexing gain will be described in detail. In the present invention, it is assumed for the sake of convenience that the distributed antenna is composed of four antenna groups, each antenna group includes four antennas, and 16 fixed beams can be formed. However, The method described below can be applied even if it is configured differently.

Two precoders are required to achieve both array gain and multiplexing gain.

과, 멀티플렉싱 이득을 얻기 위한 프리코더

가 필요하다.That is, the precoder

A pre-coder for obtaining a multiplexing gain,

.

는 수학식 1과 같이

의 함수로 표현할 수 있다.
Thus, a full precoder for simultaneously obtaining the array gain and the multiplexing gain

Is expressed by Equation (1)

Can be expressed as a function of.

의 인덱스, PMI-2는

의 인덱스)를 기지국에 보고한다.
The mobile station determines a preferred PMI (precoder matrix index) using a reference signal (RS) transmitted from the base station, and reports it to the base station. The terminal has two PMIs (PMI-1

Index, and PMI-2

To the base station.

에 대한 설명이다.Hereinafter,

.

PMI-1 is a set and the number of constituent elements equals the number of antenna groups. In the present invention, since the number of antenna groups is assumed to be 4, PMI-1 is a set of four elements.

이다. 여기서

은 미리 정의된 고정빔(fixed beam)의 수이다. 본 발명에서는 고정빔의 수를 16개로 가정하였으므로

이다.The element of PMI-1 is an integer, and the value range is

to be. here

Is the number of predefined fixed beams. In the present invention, since the number of fixed beams is assumed to be 16

to be.

인 경우 각 안테나 그룹에 대한

은 수학식 2와 같이 표현할 수 있다.

Gt; for each antenna group < RTI ID = 0.0 &

Can be expressed by Equation (2).

은

번째 안테나 그룹의

번째 고정빔을 위한

이고 4×1 벡터이다. 여기서 4는 각 안테나 그룹을 구성하는 안테나의 수이다. 따라서

은 수학식 3과 같이 나타낼 수 있다.
In Equation (2)

silver

Th antenna group

Lt; th > fixed beam

And is a 4 × 1 vector. Here, 4 is the number of antennas constituting each antenna group. therefore

Can be expressed by Equation (3).

은

번째 안테나 그룹이

번째 고정빔을 형성하기 하기 위해 사용하는 계수이다.
In Equation 3,

silver

Th antenna group

Lt; th > fixed beam.

에 대한 설명이다.Hereinafter, a precoder for utilizing the multiplexing effect

.

설명을 위하여 먼저

를 수학식 4와 같이 정의할 필요가 있다.

First,

As shown in Equation (4).

는 4×4 항등행렬(identity matrix)을 의미하고

는 하우스홀더 생성 함수 (Householder generation function)의 입력벡터(input vector)를 의미하는 것으로 표 1과 같이 정의할 수 있다. 표 1은 안테나의 수가 4인 경우

값의 예로 3GPP (3rd Generation Project Partnership) LTE (Long Term Evolution) 시스템에서 사용하는 값을 나타낸 것이다. 그러나 값은 표 1에 나타낸 값 이외의 값이 적용될 수도 있다. 또한 안테나 그룹의 수가 4가 아닌 경우에는 표 1에 나타낸 값들은 적용될 수 없고 다른 값들로 구성된

값이 적용되어야 한다.
In Equation 4,

Denotes a 4 × 4 identity matrix,

Means the input vector of the Householder Generation function and can be defined as shown in Table 1. Table 1 shows that when the number of antennas is 4

Values are values used in 3GPP (Third Generation Project Partnership) LTE (Long Term Evolution) system. However, values other than the values shown in Table 1 may be applied. If the number of antenna groups is not 4, the values shown in Table 1 can not be applied,

Value must be applied.

는 수학식 4와 표 1을 이용하여 구할 수 있다. 표 2에서

은

행렬의 첫 번째 열(column)을 의미한다.

은

행렬의 첫 번째와 두 번째 열을 의미한다.

는

행렬의 첫 번째와 네 번째 열을 의미한다.

은

행렬의 첫 번째와 두 번째 그리고 세 번째의 열을 의미한다.

은

행렬의 모든 열을 의미한다.
Table 2 shows the case where the number of antenna groups is 4, Is obtained.

Can be obtained using Equation (4) and Table 1. Table 2

silver

Means the first column of the matrix.

silver

Means the first and second columns of the matrix.

The

Means the first and fourth columns of the matrix.

silver

Means the first, second, and third columns of the matrix.

silver

It means all the columns of the matrix.

Since the number of antenna groups is 4, the possible rank of the MIMO channel is 1, 2, 3, or 4 when the number of receiving antennas of the UE is 4 or more.

는 수학식 5와 같다.
When the rank is 1

Is expressed by Equation (5).

로 보고한 경우 기지국은 전체 프리코더

를 수학식 6과 같이 설정한다.
When the terminal

The base station transmits the entire precoder

Is set as shown in Equation (6).

는

의 첫 번째 요소값을 의미하며, 각 안테나 그룹으로 입력되는 데이터

는 동일하다.

번째 안테나 그룹의

이고,

인 경우

번째 안테나 그룹의

번째 안테나에서 출력되는 신호는

이다.
in this case

The

And the data input to each antenna group

Are the same.

Th antenna group

ego,

If

Th antenna group

Lt; th >

to be.

는 수학식 7과 같다.
When the rank is 2

Is expressed by Equation (7).

로 보고한 경우 기지국은 전체 프리코더

를 수학식 8과 같이 설정한다.
When the terminal

The base station transmits the entire precoder

Is set as shown in Equation (8).

는

의 첫 번째 열,

는

의 두 번째 열을 의미한다. 또

는

의

번째 요소값을 의미한다. 따라서,

이고

이다. 각 안테나 그룹으로 입력되는 값은

의 선형결합값(linearly combined value)이다.

번째 안테나 그룹의

이고,

인 경우

번째 안테나 그룹의

번째 안테나에서 출력되는 신호는

이다.
in this case

The

In the first column,

The

&Quot; In addition

The

of

Quot; < / RTI > therefore,

ego

to be. The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

to be.

는 수학식 9와 같다.
When the rank is 3

Is expressed by Equation (9).

로 보고한 경우 기지국은 전체 프리코더

를 수학식 10과 같이 설정한다.
When the terminal

The base station transmits the entire precoder

Is set as shown in Equation (10).

는

의 첫 번째 열,

는

의 두 번째 열,

는

의 세 번째 열을 의미한다. 각 안테나 그룹으로 입력되는 값은

의 선형결합값(linearly combined value)이다.

번째 안테나 그룹의

이고,

인 경우

번째 안테나 그룹의

번째 안테나에서 출력되는 신호는

이다.
in this case

The

In the first column,

The

The second column,

The

&Quot; The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

to be.

는 수학식 11과 같다.
When the rank is 4

Is expressed by Equation (11).

로 보고한 경우 기지국은 전체 프리코더

를 수학식 12와 같이 설정한다.
When the terminal

The base station transmits the entire precoder

Is set as shown in Equation (12).

는

의 첫 번째 열,

는

의 두 번째 열,

는

의 세 번째 열,

는

의 네 번째 열을 의미한다. 각 안테나 그룹으로 입력되는 값은

의 선형결합값(linearly combined value)이다.

번째 안테나 그룹의

이고,

인 경우

번째 안테나 그룹의

번째 안테나에서 출력되는 신호는

이다.
in this case

The

In the first column,

The

The second column,

The

The third column,

The

The fourth column of the second column. The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

to be.

The signal transmission method using multiple antennas according to the embodiment of the present invention can be used for individual application of SU-MIMO (Single User MIMO) or MU-MIMO (Multi User MIMO), or simultaneous application of SU-MIMO and MU- .

7 is a conceptual diagram illustrating a signal transmission method using multiple antennas according to an embodiment of the present invention.

FIG. 7 shows an example in which a base station provides services by simultaneously applying SU-MIMO and MU-MIMO to terminals spaced apart from each other.

It is assumed that the base station has four antenna groups 310 to 340 and that each antenna group includes four antennas and that each of the terminals 731, 732, and 733 can have a maximum of four antennas The maximum rank is 4.

Referring to FIG. 7, a terminal 731 can receive a signal through four beams 751 formed by a base station using four antenna groups 310 to 340. Also, the terminal 732 can receive signals through the four beams 752 formed by the base station using four antenna groups. Since the beams 751 directed toward the terminal 731 and the beams 752 emitted toward the terminal 732 are different in direction from each other, the base station uses the same spectrum to transmit the signals to the terminal 731 and the terminal 732 At the same time, different signals can be transmitted. In this case, the terminals 731 and 732 can receive up to four multiplexed signals at the same time.

Each of the terminals 731, 732, and 733 selects the rank, PMI-1, and PMI-2 based on the reference signal transmitted from the base station and reports it to the base station as described later.

On the other hand, assuming that the terminal 731 has four reception antennas, the maximum value of the rank that the MIMO channel between the base station and the terminal 731 can have is four. Therefore, the base station can transmit a signal to the terminal 731 by reusing the spectrum by the maximum number of reported ranks with reference to the rank, PMI-1, and PMI-2 reported from the terminal. That is, the base station can transmit a signal to one terminal using the SU-MIMO scheme using a plurality of antenna groups.

The base station can also perform MU-MIMO based on the channel information (rank, PMI-1, PMI-2) reported from the terminal 732 and the terminal 733, respectively.

을 사용하고 서로 다른

를 사용할 경우, 기지국은 MU-MIMO를 사용하여 두 단말에게 신호를 전송할 수 있다.When the terminal 732 and the terminal 733 are the same

And use different

, The base station can transmit signals to the two terminals using MU-MIMO.

을 사용하고 랭크가 2인 서로 다른

를 사용할 경우, 기지국은 단말 별로 랭크 2의 프리코딩을 적용할 수 있으므로 SU-MIMO, MU-MIMO의 동시 적용도 가능하다.
For example, when the terminal 732 and the terminal 733 are the same

And the rank is 2

, The BS can apply the rank 2 precoding for each UE, so it is possible to apply the SU-MIMO and the MU-MIMO simultaneously.

Hereinafter, a channel information reporting method of a terminal will be described.

The UE reports the rank, PMI-1, and PMI-2 of the MIMO channel existing between the transmission antenna of the base station and the reception antenna of the UE to the base station.

The UE can measure the rank, PMI-1 and PMI-2 of the MIMO channel using the reference signal transmitted by the base station. In addition, a time-frequency resource must be allocated to the downlink so that the base station can transmit the reference signal.

The reference signal may be transmitted without applying precoding, but it is assumed that the reference signal is transmitted by applying precoding in the embodiment of the present invention.

The reference signal can be generated using a PN (Pseudo Noise) sequence and an OCC (Orthogonal Cover Code).

프리코딩만 적용하고

프리코딩은 적용하지 않고 전송할 수도 있다. Also, the reference signal is

Apply precoding only

Precoding can also be applied without applying.

프리코딩을 적용하여 전송하면, 서로 다른

을 사용하는 빔들은 공간적으로 서로 이격되어 있으므로 각 안테나 그룹이 형성하는 N개의 고정빔으로 전송되는 기준신호는 동일한 시간-주파수 자원을 이용할 수 있다. 그러나 이 경우, 서로 인접한 빔들 사이의 간섭으로 단말의 기준신호 검출 성능이 저하될 수 있다.To the reference signal

When precoding is applied and transmitted,

Are spaced apart from each other, the reference signals transmitted by the N fixed beams formed by the antenna groups can use the same time-frequency resources. In this case, however, the reference signal detection performance of the UE may be degraded due to interference between adjacent beams.

In order to mitigate inter-beam interference, adjacent beams may transmit reference signals using different resources without using the same resources.

Or, to mitigate interference between beams, all beams may be transmitted using the same time-frequency resource, but different times of reference signal transmission may be determined. That is, a specific antenna group may transmit a reference signal using a time division multiplexing (TDM) method.

8 is a conceptual diagram for explaining a reference signal transmission method according to an embodiment of the present invention. 8 shows an example of a time division multiplexing method as an example of a reference signal transmission method.

을 사용하는 고정빔이 4개 존재한다. 따라서, 동일한

을 사용하는 고정빔을 구분하기 위한 4가지의 기준신호가 필요하다.
When the base station has four antenna groups,

There are four fixed beams using a fixed beam. Therefore,

It is necessary to use four reference signals for distinguishing the fixed beam using the reference beam.

As shown in FIG. 8, each antenna group of the base station transmits a precoded reference signal to a fixed beam 0 in a time period (n). In this case, precoding applied to each antenna group is expressed by Equation (13).

The time-frequency resource for the four reference signal transmissions may be composed of four adjacent REs (Resource Elements) as shown in FIG.

Also, the base station can transmit four reference signals precoded into the fixed beam 1 in the time interval n + 1, and four reference signals precoded in the fixed interval 2 in the time interval n + 2. In this case, assuming that the number of types of values that the PMI-1 can have is N, in the time interval n + N-1, Four reference signals precoded into N-1 are transmitted.

The length of the time interval in which the reference signal shown in FIG. 8 is transmitted and the density of the frequency interval may be different depending on the environment.

In order to mitigate inter-cell interference and inter-beam interference, a PN sequence may be used as a reference signal, and a PN sequence generator initialization value may include a cell ID, a beam ID ), A time interval index, and the like. The PN sequence generated on a time interval basis is mapped to the resource element allocated to the reference signal transmission in the corresponding time interval.

개 할당되어 있다면 필요한 PN 시퀀스의 길이는

가 된다.
In order to transmit the reference signal in one time interval, four adjacent resource elements

If it is assigned, the length of the required PN sequence is

.

Time division multiplexing (TDM), Frequency Division Multiplexing (FDM), or Code Division Multiplexing (CDM) may be used as a method for distinguishing four reference signals transmitted in each time interval, In the present invention, a case of using code division multiplexing will be described by way of example.

In FIG. 8, resource allocation including four adjacent resource elements is illustrated to transmit four reference signals.

가 있다. 여기서

을 안테나 그룹 0,

을 안테나 그룹 1,

를 안테나 그룹 2,

을 안테나 그룹 3에 할당하면 각 안테나 그룹을 구분할 수 있다.
Here, each antenna group can be distinguished from the reference signal by using OCC such as a length-4 hardamard sequence. There are four Hadamard sequences of length 4

. here

Antenna group 0,

Antenna group 1,

Antenna group 2,

To the antenna group 3, it is possible to distinguish each antenna group.

프리코딩이 적용된다.A time-frequency assignment consisting of four adjacent resource elements is used to transmit the value multiplied by the OCC to the PN,

Precoding is applied.

In order to prevent performance degradation due to collision of reference signals transmitted in each cell, hopping may be applied at the time of transmitting a reference signal.

Hereinafter, a method of generating a demodulation reference signal (DMRS) applied to a signal transmission method using multiple antennas according to an embodiment of the present invention will be described.

The base station transmits a demodulation reference signal to demodulate the data received by the terminal when transmitting data to the terminal. The above-mentioned reference signal RS is transmitted to all terminals because it is to help determine the rank of the terminals, PMI-1, and PMI-2.

On the other hand, since the demodulation reference signal DMRS is for demodulating a specific terminal, it is transmitted for a specific terminal rather than all the terminals. Accordingly, the reference signal and the demodulation reference signal are preferably transmitted using different time-frequency resources.

The demodulation reference signal is formed by multiplying the generated PN and OCC for the demodulation reference signal. Since the demodulation reference signal is a UE-specific signal while the reference signal is a cell and a beam specific signal, a UE identifier is required in addition to a cell identifier, a beam delimiter, and a time interval index at the time of initializing the PN generator. The OCC may be the same as the OCC used in generating the reference signal. The OCC used in the demodulation reference signal is not for distinguishing antenna groups but for distinguishing the rank (or layer) of data that is multiplexed and transmitted.

이 적용된다.
The demodulation reference signal and data include the same precoding

Is applied.

Hereinafter, a method for improving cell boundary performance and managing inter-cell interference in a signal transmission method using multiple antennas according to an embodiment of the present invention will be described.

9 is a conceptual diagram for explaining a method of applying a signal transmission method using multiple antennas to a cell boundary region according to an embodiment of the present invention.

9, a first terminal 911 and a second terminal 912 are connected to a first cell in which a first base station 901 provides service and a boundary region of a second cell in which a second base station 902 provides services And the first base station 901 is assumed to be the serving base station of the first terminal 911 and the second terminal 912.

The first terminal 911 can determine the PMI-1 using Equation (14) using the reference signal transmitted by the four antenna groups of the first base station 901.

는 제1 기지국(901), 안테나 그룹

의 고정빔

를 의미한다.

A first base station 901,

Fixed beam

.

Similarly, the first terminal 911 can determine PMI-1 for the second base station 902 as shown in Equation (15).

에서 몇 개의 빔을 선택할 수 있다. 예를 들어 제1 단말(911)은

를 선택하고, 이 4개의 고정빔에 대하여 PMI-2를 결정할 수 있다.The first terminal 911, which calculates the PMI-1 for the serving BS and the neighbor BS,

You can select several beams at. For example, the first terminal 911

, And PMI-2 can be determined for these four fixed beams.

The first terminal 911 reports PMI-1 and PMI-2 to the first base station 901 serving as a serving base station and the first base station 901 reports to the first terminal 911 through the inter- And notifies the second base station 902 of one PMI-1 and PMI-2 information. If communication between the first base station 901 and the second base station 902 is difficult, the first terminal 911 transmits PMI-1, the second base station 902, and the second base station 902 to the first base station 901 and the second base station 902 through the uplink, PMI-2 may be simultaneously reported.

As described above, the first base station 901 and the second base station 902 perform cooperative precoding based on the reported PMI-1 and PMI-2 to determine the reception performance of the first terminal 911 Can be improved. The first base station 901 and the second base station 902 may transmit the first terminal 911 and the second terminal 912 to the first terminal 911 and the second terminal 912 in consideration of the information reported by the first terminal 911 and the second terminal 912, MU-MIMO scheduling may be performed to improve spectrum utilization efficiency.

In an embodiment of the present invention, a terminal selects four beams out of eight beams formed from two base stations and reports the selected beams to the serving base station, but the technical idea of the present invention is not limited thereto. That is, in another embodiment of the present invention, the terminal may be configured to select and report a different number of beams than four. However, in this case, a new precoder design is required.

As described above, the signal transmission method using multiple antennas according to the embodiment of the present invention can be applied not only to a data channel but also to a control channel, thereby dramatically increasing the capacity of the system.

First, a case of using a signal transmission method using multiple antennas according to an embodiment of the present invention for transmission of a data channel will be described.

The UE determines the rank, PMI-1, and PMI-2 using the reference signal received from the base station, and then reports the determined information to the base station.

Here, the maximum number of ranks that can be determined by the UE can be given by Equation (16).

In the above-described embodiment of the present invention, since the base station has four antenna groups and the number of receiving antennas is four, SU-MIMO can be applied up to four layers.

In addition, MU-MIMO can be applied to UEs that have different PMI-2 from the UEs reporting the same PMI-1 information to the base station. For example, if two UEs with a rank of 2 report the same PMI-1 information to a BS, and if the two UEs have different PMI-2s, the two UEs can each be served in two layers .

In addition, in the signal transmission method using multiple antennas according to the embodiment of the present invention, joint MIMO (joint MIMO) is applied to terminals located in a cell boundary region, thereby improving reception performance of terminals located in a cell boundary region , The inter-cell interference can be efficiently managed.

In the case of spatial multiplexing (SM) using the multiplexing effect, since the required signal-to-noise ratio is high, it is not likely to be applicable at the edge of the service area of the base station. In this case, when the array gain is used, the capacity of the system can be increased by expanding the area where the multiplexing effect can be utilized.

Hereinafter, a case of using a signal transmission method using multiple antennas according to an embodiment of the present invention for transmission of a control channel will be described.

The control channel is transmitted to all terminals other than the specific terminal. Thus, the base station shapes the beam so as to support the entire service area without shaping the beam in a specific direction for transmission of the control channel. Hereinafter, a beam to be formed by a base station is referred to as an omni beam in order to support the entire service area. The beam width of the omnidirectional beam may be 120 degrees or 360 degrees depending on the shape of the cell.

가 사용되지 않으므로

이 된다. 또한

은 전체 서비스 영역을 지원할 수 있는 빔을 의미하므로, 이하에서

로 표현한다.

는 미리 정의된 값이므로 기지국은 단말로부터 랭크, PMI-1, PMI-2를 보고받을 필요가 없다. 또한, 단말은 기지국이 안테나 그룹의 수만큼 송신 안테나를 구비한 것으로 인식한다.
The control channel includes a pre-

Is not used

. Also

Denotes a beam capable of supporting the entire service area,

.

Is a predefined value, the BS does not need to receive the rank, PMI-1, and PMI-2 from the UE. In addition, the terminal recognizes that the base station has as many transmission antennas as the number of antenna groups.

가 적용되어 전송되어야 한다. The base station does not transmit a reference signal for the control channel. However, the base station must transmit a control channel demodulation reference signal (CCDMRS) that supports the coherent demodulation of the control channel. The control channel demodulation reference signal is the same precoding as applied to the control channel, i. E.

Must be applied and transmitted.

Meanwhile, in the signal transmission method using multiple antennas according to the embodiment of the present invention, a transmit diversity technique can be applied to control channel transmission according to the number of antenna groups. In this case, the terminal must be able to distinguish the control channel demodulation reference signal transmitted by each antenna group. The control channel demodulation reference signal transmitted by each antenna group can be multiplexed and transmitted by TDM, FDM, CDM, or the like.

For example, Space Frequency Block Coding (SFBC) can be applied when the number of antenna groups is 2. When the number of antenna groups is 4, techniques such as Frequency Switched Transmit Diversity (FSTD) and Full Diversity Full Rate Can be applied.

As described above, the signal transmission method using multiple antennas according to the embodiment of the present invention can be applied to cooperative MIMO by cooperation between a control channel, a data channel, and a base station.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

101: array antenna 103: precoder
200: multiple antennas 210: antenna group 0
211: antenna 220: antenna group 1
221: antenna 230: antenna group 2
231: antenna 240: antenna group 3
241: Antenna 300: Multiple antennas
310: Antenna Group 0 311: Antenna
320: antenna group 1 321: antenna
330: antenna group 2 331: antenna
340: antenna group 3 341: antenna
400: Multiple antennas 410: Antenna group 0
411: antenna 420: antenna group 1
421: antenna 430: antenna group 2
431: antenna 440: antenna group 3
441: Antennas 601, 602, 603, 604: Fixed beam
731, 732, 733: Terminals 751, 752:
901: first base station 902: second base station
911: first terminal 912: second terminal

Claims (20)

In the radio signal transmission method,
Wherein a plurality of antenna groups are arranged to obtain an array gain and a multiplexing gain at the same time so that the distance between the antenna groups is kept apart so that there is no correlation therebetween and there is a correlation between antennas constituting each antenna group. Signal transmission method using antenna In a signal transmission method performed at a base station,
The base station transmitting a reference signal for each of the antenna groups and the directional beam;
Calculating a first precoder matrix index (PMI-1) and a second matrix index (PMI-2) using the reference signal, and reporting the first precoder matrix index and the second matrix index to a base station; And
The base station performing precoding on the downlink data and the demodulation reference signal based on a first precoder corresponding to the first precoder matrix index and a second precoder corresponding to the second precoder matrix A method of transmitting signals using multiple antennas. The method of claim 2,
Wherein the first precoder is a precoder for shaping a directional beam of each of a plurality of antenna groups and the second precoder is a precoder for obtaining a multiplexing gain using a directional beam formed by each of the plurality of antenna groups Wherein the plurality of antennas are used for transmitting signals. The method of claim 2,
Wherein the reference signal is generated using a PN (Pseudo-Noise) sequence and an OCC (Orthogonal Cover Code) sequence. The method of claim 4,
Wherein the reference signal is generated by multiplying the PN sequence by one of the number of OCC sequences equal to the number of antenna groups for inter-cell interference and inter-beam interference mitigation and for directional beam division transmitted by each antenna group. Method of signal transmission using The method of claim 4,
Wherein the PN sequence is initialized in units of a predetermined time interval. The method of claim 4,
Wherein at least one of a cell delimiter, a beam delimiter, and an index of a predetermined time interval is used as an initial value of the PN sequence. The method of claim 2,
Wherein the step of transmitting the reference signal comprises:
Wherein the reference signal is precoded by applying only the first precoder to the reference signal without applying the second precoder, and then the reference signal is transmitted. The method of claim 2,
In the step of transmitting a reference signal by a plurality of antenna groups,
Wherein a reference signal to which an adjacent directional beam is applied is not transmitted at the same time using the same time-frequency resource for the purpose of mitigating interference between neighboring directional beams formed by the same antenna group. The method of claim 2,
Wherein the step of transmitting the reference signal comprises:
In the reference signal to which the plurality of antenna groups are formed, if the directions of the beams formed by the antenna groups are the same, transmission is performed using the same time-frequency resource but antenna groups are divided using PN and OCC Signal transmission method using multiple antennas The method of claim 2,
Wherein the step of performing precoding on the downlink demodulation reference signal comprises:
Generating a demodulation reference signal by multiplying a PN sequence initialized using at least one of the terminal identifier, a cell identifier, a beam delimiter, and a preset time interval index by an OCC sequence;
Performing pre-coding on the generated demodulation reference signal by applying the same precoder as the first precoder and the second precoder applied to the downlink data; And
And transmitting the downlink transmission signal including the precoded downlink data and the demodulation reference signal to the mobile station. The method of claim 2,
The first precoder

) According to the first precoder matrix index (PMI-1) received from the terminal according to the following equation

silver

Th antenna group

And a second fixed beam, respectively.

The method of claim 2,
In the data transmission step,

And the rank is 1, the precoder can be expressed by the following equation

Lt; RTI ID = 0.0 >

And the data input to each antenna group

Are the same.

Th antenna group

ego,

If

Th antenna group

Lt; th >

) Is determined as Equation (3).

The method of claim 2,
In the data transmission step,

And the rank is 2, the precoder can be expressed by the following equation

Lt; RTI ID = 0.0 >

In the first column,

The

&Quot; In addition

The

of

Quot; < / RTI > therefore,

ego

to be. The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

) Is determined as Equation (3).

The method of claim 2,
In the data transmission step,

And the rank is 3, the precoder can be expressed by the following equation

Lt; RTI ID = 0.0 >

In the first column,

The

The second column,

The

&Quot; The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

) Is determined as Equation (3).

The method of claim 2,
In the data transmission step,

And the rank is 4, the precoder can be expressed by the following equation

Lt; RTI ID = 0.0 >

In the first column,

The

The second column,

The

The third column,

The

The fourth column of the second column. The value input to each antenna group is

(Linearly combined value).

Th antenna group

ego,

If

Th antenna group

Lt; th >

) Is determined as Equation (3).

In a signal transmission method performed at a base station,
Transmitting a reference signal through a directional beam formed by each of the individual antenna groups in a plurality of antenna groups;
Calculating a first MIMO channel rank, a first precoder matrix index and a second precoder matrix index using the reference signal and reporting the MIMO channel rank to a first base station; And
Determining a MIMO transmission scheme to be applied to at least one of the plurality of terminals based on the rank of the received plurality of terminals, the first precoder matrix index, and the second precoder matrix index information, Transmission method. 18. The method of claim 17,
Wherein the determining of the MIMO transmission scheme to be applied to the at least one terminal comprises:
MU-MIMO or SU-1 based on the reported rank, PMI-1 and PMI-2 when the PMI-1 reported by the first terminal and the second terminal is different or when the PMI- -MIMO / MU-MIMO simultaneously to transmit downlink data. A cooperative signal transmission method performed in a first base station and a second base station,
The step of the terminals receiving the rank, the first precoder matrix index and the second precoder matrix index information,
The UE determines the preferred PMI-1 and PMI-2 for both base station antenna groups according to the reference signals transmitted by the first base station and the second base station, and reports to both the first base station and the first base station and the second base station ;
Providing the first base station with channel information reported by the terminal through the inter-base station interface to the second base station when the terminal reports only to the second base station; And
The first base station and the second base station cooperate with each other to improve the received signal-to-noise ratio, inter-cell interference mitigation or system capacity increase based on the channel information reported by the first and second base stations, The method comprising: applying MIMO; In the control channel transmission,
The base station uses each antenna group to perform a first precoding

And multiplexes the control channel demodulation reference signal for each group by a method such as TDM, CDM, FDM or the like so that the terminal can distinguish the antenna group, and performs the first precoding

To transmit control channel transmission diversity.

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