KR101969018B1 - Precoding method for multi-user multiple-antenna system and apparatus therefor - Google Patents

Abstract

The present disclosure relates to a method and apparatus for pre-coding in a multi-user multi-antenna system.
A method and apparatus for pre-coding in a multi-user multi-antenna system are disclosed. A method for downlink transmission by a first device having a plurality of antennas, the method comprising: acquiring downlink channel information for each of a plurality of second devices having a plurality of antennas, based on the downlink channel information; Coding matrix so as to maximize the sum of the transmission rates of the plurality of second devices in consideration of the constraint on the total transmission power in the first device, and determine a second pre-coding matrix based on the first pre- Encoding matrix that is closest to the acquired reference matrix among the pre-coding matrices satisfying the constraint on the transmission power of each of the plurality of antennas of the first device, Coding matrix, and transmits the data stream using the second pre-coding matrix.

Description

[0001] PRECODING METHOD FOR MULTI-USER MULTIPLE-ANTENNA SYSTEM AND APPARATUS THEREFOR [0002]

The present disclosure relates to a pre-coding method and apparatus in a multi-user multiple-input multiple-output antenna system.

A multi-input multi-output (MIMO) system using multiple transmit / receive antennas has been introduced to solve the equations such as fading, propagation attenuation, and interference between terminals. A base station or a router in a MIMO system simultaneously transmits multiple data streams to a mobile station using a spatial multiplexing transmission scheme in order to maximize traffic. At this time, in order to maximize the data rate of the multiple data streams, the base station or the router uses a precoder code. In particular, in a downlink supporting multiple access, signals transmitted to a plurality of terminals can be simultaneously transmitted through a MIMO channel in the same band. At this time, the base station or the router uses different pre-coding codes for signals transmitted to the respective terminals in order to reduce interference between signals of the plurality of terminals and increase the transmission rate of the terminals.

When designing a pre-coded code for a MIMO system, the total transmission power constraint for the downlink is considered so that the sum of the power transmitted from the antennas of all base stations is equal to or less than a predetermined maximum transmission power. The total transmission power constraint is applied to the pre-coding code design when the transmission power between a plurality of transmission antennas can be shared with each other and the transmission power of each antenna can be arbitrarily changed within the entire transmission power range. When the total transmission power constraint is applied to the pre-coding code design, the power allocated to each antenna varies according to the state of the channel, so that the transmission signal of each antenna has a high peak-to-average power ratio (PAPR) The power efficiency of the power amplifier is lowered. Also, in the case of a distributed antenna system, since a plurality of transmission antennas are physically separated, there is a mathematical expression that can not consider the total transmission power constraint. Recently, studies are being made on a pre-coding code design technique considering transmission power constraints for each antenna that limits the transmission power of each antenna of a base station to a certain level or less.

However, when a pre-coding code is designed so that the sum of the transmission rates of all terminals is maximized in a MU-MIMO (Multi User-Multi Input Multi Output) system considering transmission power constraints for each antenna, Since there is no closed-form solution, the solution must be solved using an iterative algorithm based on numerical analysis. That is, the design of the pre-coding code that satisfies the transmission power constraint for each antenna is very complex. Accordingly, there is a need for a technique for designing a pre-coding code with a low complexity in an MU-MIMO system considering transmission power limitation for each antenna.

The present disclosure provides a method and apparatus for designing a pre-coded code that meets transmit power constraints for each antenna with low complexity.

The present disclosure provides a method and apparatus for providing a pre-encoded code that satisfies the transmit power constraint for each antenna and maximizes the downlink transmission rate sum of each UE under the total transmission power constraint.

A method for downlink transmission by a first device having a plurality of antennas according to the present invention includes the steps of: obtaining downlink channel information for each of a plurality of second devices having a plurality of antennas, Determining a first pre-coding matrix such that a sum of data rates of the plurality of second devices is maximized considering a constraint condition on the total transmission power of the first device based on downlink channel information; 1 matrix among the pre-coding matrices satisfying the constraint on the transmission power of each of the plurality of antennas of the first device based on the first reference matrix and the second reference matrix, Determining a pre-coding matrix closest to the first pre-coding matrix as a second pre-coding matrix; It characterized in that it comprises the step of transmitting the data stream.

A first device having a plurality of antennas according to the present disclosure includes a transmitter and receiver for obtaining downlink channel information for each of a plurality of second devices having a plurality of antennas, Determining a first pre-coding matrix such that the sum of the transmission rates of the plurality of second devices is maximized taking into account the constraint on the total transmission power in the first device, and based on the first pre- Obtaining a reference matrix for a second pre-coding matrix, and based on a constraint on transmission power at each of a plurality of antennas of the first device, a pre-coding matrix closest to the obtained reference matrix among the pre- Coding matrix, and to transmit the data stream using the second pre-coding matrix, And a control unit for controlling the receiving unit.

1 is a diagram illustrating a data stream transmission method in an MU-MIMO system to which a pre-coding code according to an embodiment of the present disclosure is applied.
FIG. 2 is a diagram illustrating a method of determining a pre-coding code in an MU-MIMO system according to an embodiment of the present disclosure.
3 is a diagram illustrating a method for determining a first pre-encoder according to an embodiment of the present disclosure.
4 is a diagram illustrating a method for determining a second pre-encoder according to an embodiment of the present disclosure.
5 is a diagram illustrating a method of precoding a transmission symbol vector based on a second pre-coding code according to an embodiment of the present disclosure.
6 is a diagram showing a configuration of a base station according to an embodiment of the present disclosure.
7 is a diagram showing a configuration of a terminal according to an embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

In describing the embodiments, descriptions of techniques which are well known in the art to which the embodiments of the present disclosure belong, and which are not directly related to the embodiments of the present disclosure will not be described. This is for the sake of clarity without omitting the gist of the embodiments of the present disclosure by omitting the unnecessary explanation.

For the same reason, some of the components in the drawings are exaggerated, omitted, or schematically illustrated. Also, the size of each component does not entirely reflect the actual size. In the drawings, the same or corresponding components are denoted by the same reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the embodiments of the present disclosure, and how to accomplish them, will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the specific details set forth herein below except that the embodiments of the present disclosure are intended to be illustrative only, And the claims of this disclosure are only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

At this point, it will be appreciated that the combinations of blocks and flowchart illustrations in the process flow diagrams may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, so that those instructions, which are executed through a processor of a computer or other programmable data processing apparatus, Thereby creating means for performing functions. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory The instructions stored in the block diagram (s) are also capable of producing manufacturing items containing instruction means for performing the functions described in the flowchart block (s). Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible for the instructions to perform the processing equipment to provide steps for executing the functions described in the flowchart block (s).

In addition, each block may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative implementations, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may actually be executed substantially concurrently, or the blocks may sometimes be performed in reverse order according to the corresponding function.

Herein, the term " part " used in the present embodiment means a hardware component such as software or an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) Lt; / RTI > However, 'part' is not meant to be limited to software or hardware. &Quot; to " may be configured to reside on an addressable storage medium and may be configured to play one or more processors. Thus, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, the components and components may be implemented to play back one or more central processing units (CPUs) within a device or a secure multimedia card.

It is to be understood that the subject matter underlying the subject matter may be applied to other communication systems and services having similar technical backgrounds without departing from the scope of the disclosure herein as it is understood by those skilled in the art .

The method of designing a pre-coded code according to the present invention is not limited to maximizing a rate of a terminal, and when a plurality of pre-coded codes are applied to a transmission rate having a smallest value among the rates of the terminals, It is possible to apply the structure change at a common level even when the rate of the terminal is minimized to the probability that the base station rate is lowered (outage). In addition, since the present invention considers the MU-MIMO system, the present invention can be applied to a multi-user multi-input single-output (MU-MISO) system including SU-MIMO It is possible to apply the proposed pre-coding code design method.

1 is a diagram illustrating a data stream transmission method in an MU-MIMO system to which a pre-coding code according to an embodiment of the present disclosure is applied.

1, the base station 100 in the MU-MIMO system 1000 includes Nt antennas, and the K terminals 200-1, 200-2, .., and 200-K include N _rK Antennas. At this time, the downlink channel H _k corresponding to the terminal K is represented by an N _rK x N _t matrix.

The base station 100 first obtains downlink channel information for each of the terminals 200-1, 200-2, ..., and 200-K, and uses the downlink channel information to perform an optimal pre- Code, and then determines a second pre-coding code that is an optimal pre-coding code under the entire transmission power constraint, taking into consideration the transmission power constraint for each antenna. At this time, the base station 100 determines the second pre-coding code considering the transmission power limitation for each antenna from the viewpoint of minimizing the Minimum Mean Square Error (MSE). In addition, the base station 100 converts a mathematical expression for determining a second pre-coding code under a total transmission power constraint into a dual optimization problem in consideration of a transmission power constraint for each antenna, Reduce. The second pre-coded code determined for terminal K is represented by N _t x N _{s, K} matrix W _k .

The base station 100 transmits data to each of the terminals 200-1, 200-2, ..., 200-K simultaneously in order to simultaneously transmit a plurality of data streams in the same frequency band through spatial multiplexing based on pre- Performs serial-to-parallel (S / P) conversion after each symbol modulation, and determines a transmission symbol vector. At this time, the S / P conversion is performed for transmission of multiple data streams. The transmit symbol vector is a vector for the data symbol.

Assuming that the number of symbols simultaneously transmitted to the terminal K (200-K) is N _{s, K} , the transmission symbol vector b _{k, which} is a symbol vector transmitted to the terminal K, is represented by N _{s and K} x 1 vectors. The base station 100 generates a final transmission symbol vector to be transmitted to the terminal 200 by applying a second pre-coding code to the transmission symbol vector b _k , and transmits the transmission signal corresponding to each element of the final transmission symbol vector to the multiple data streams To the terminals 200-1, 200-2, .., and 200-K simultaneously. The terminals 200-1, 200-2, ..., and 200-K receive the transmission signals and transmit the transmission signals to the terminals 200-1, 200-2, .., 200-K based on the transmission signals. And restores the corresponding data stream.

In FIG. 1, the base station 100 has been described as an example for convenience of description. However, the base station 100 may be implemented as a router, a repeater, or the like without limitation.

FIG. 2 is a diagram illustrating a method of determining a pre-coding code in an MU-MIMO system according to an embodiment of the present disclosure.

Referring to FIG. 2, in step 201, the BS acquires downlink channel information for each MS.

For example, in a Frequency Division Duplex (FDD) system, a UE estimates downlink channel information using a preamble, a pilot, a reference signal, etc., which are known in advance, And transmits the downlink channel information to the base station.

Also, for example, when the symmetry of the uplink channel and the downlink channel is ensured in a time division duplex (TDD) system, the uplink channel is used in the downlink in the same manner. On the other hand, when the symmetry of the uplink channel and the downlink channel is not ensured in the time division duplexing system, the terminal estimates the downlink channel information in the same manner as the frequency division duplexing system and transmits the downlink channel information to the base station, And acquires channel information.

In step 202, the BS determines a first pre-coding code based on the downlink channel information so as to maximize the sum of the transmission rates of the respective terminals in consideration of the total transmission power constraint.

A concrete first pre-coding code determination method will be described later with reference to FIG.

The base station determines in step 203 a second pre-encoding code under a per-antenna transmit power constraint based on the first precoder.

Specifically, the base station determines a first pre-encoding code and a second pre-encoding code considering the transmit power constraint for each antenna using the calculated parameters while determining the first pre-encoding code and the first pre-encoding code determined under the total transmit power constraint. At this time, the distance between the first pre-coding code determined under the total transmission power constraint and the second precoded code determined under the transmission power constraint for each antenna is made minimum in the MSE standard. In the present invention, for convenience of description, the distance between the first and second pre-coded codes in the MSE standard is defined as an L2-norm distance. The distance between the first and second pre-coded codes can be transformed into an L1-norm distance based on an absolute value, an L3-norm distance based on a third power, and the like, if necessary.

A concrete second pre-coding code determination method will be described later with reference to FIG.

In step 204, the base station pre-encodes the transmission symbol vector based on the second pre-coding code.

That is, the base station updates the pre-coding code used before determining the second pre-coding code to the second pre-coding code, and pre-codes the transmission symbol vector based on the second pre-coding code. The transmission symbol vector is pre-coded and transmitted to each terminal. The pre-coded code used before determining the second pre-coded code may be a pre-coded code predetermined by the base station.

A concrete transmission symbol pre-coding method will be described later with reference to FIG.

Hereinafter, for convenience of description, it is defined that the number of antennas of each terminal is the same, and the number of data streams simultaneously transmitted to each terminal is the same.

The number of antennas of each terminal is defined as follows.

The number of data streams of each terminal is defined as follows.

However, the present invention is also applicable to the case where the number of antennas of each terminal is different and the number of data streams transmitted to each terminal is different at the same time.

3 is a diagram illustrating a method for determining a first pre-encoder according to an embodiment of the present disclosure.

Referring to FIG. 3, in step 301, the BS defines a mathematical expression that maximizes a summation rate of all MSs considering a total transmission power constraint.

Specifically, a base station defines a mathematical expression by applying a ZF (zero forcing) transmission scheme in order to exclude interference between signals of the UE.

The defined mathematical formula is shown in Equation (1) below.

[Equation 1]

은 잡음의 분산을 나타내고, P_sum은 최대 송신 전력을 의미한다. 수학식 1의 목적식은 모든 단말의 합산 전송률을 나타낸다. 첫 번째 제약식은 K개의 단말에 전송되는 전송 전력의 합이 최대 전송 전력 이하가 되어야 한다는 전체 전송 전력 제약을 의미하며, 두 번째 제약식은 단말 간 간섭이 0이 되도록 하기 위한 ZF 전송 조건을 나타낸다. 두 번째 제약식을 만족하는 해가 존재하기 위해서는 N_t≥KN_r의 조건을 만족해야 한다.At this time, the pre-coded code W _k of the terminal k is defined as an M x L complex matrix, I _N denotes an N x N unit matrix,

Denotes the variance of the noise, and P _sum denotes the maximum transmission power. The objective equation of Equation (1) represents the summation rate of all terminals. The first constraint expresses the total transmission power constraint that the sum of the transmission powers transmitted to the K terminals should be less than the maximum transmission power and the second constraint expresses the ZF transmission condition for the inter-terminal interference to be zero. In order for a solution satisfying the second constraint to exist, N _t ≥ KN _r must be satisfied.

In step 302, the BS applies a SVD (Singular Value Decomposition) based block diagonalization method to each of the interference channels of the UEs.

Here, SVD means singular value decomposition.

는 하기의 수학식 2와 같이 정의된다.The interference channel of terminal k

Is defined by the following equation (2).

&Quot; (2) "

는

행렬이 된다. 간섭 채널

에 SVD를 적용하면 하기의 수학식 3과 같이 분해된다. here,

The

Matrix. Interference channel

SVD is decomposed as shown in Equation (3) below.

&Quot; (3) "

이라고 정의하면,

는

Unitary Matrix이고,

는

대각 행렬로 내림차순으로 정렬되며,

는

Unitary Matrix을 나타낸다.

은

의 처음부터

까지의 열 벡터로 구성되는 행렬이고,

(제1 파라미터)는

의 마지막 L개의 열 벡터로 구성되는 행렬로

의 Null Space에 대응된다. 단말 신호간의 잡음을 제거하기 위해 단말 K의 제1 사전부호화코드에

를 사용하는 경우 유효 채널(Effective Channel)은 하기의 수학식 4와 같이

행렬

로 주어진다.Here, L =

≪ / RTI >

The

Unitary Matrix,

The

Are arranged in descending order by a diagonal matrix,

The

Represents a Unitary Matrix.

silver

From the beginning of

Lt; RTI ID = 0.0 > 1, < / RTI >

(First parameter)

Lt; RTI ID = 0.0 > L < / RTI >

Corresponding to the null space of FIG. In order to remove the noise between the terminal signals, the first pre-

The Effective Channel is expressed as Equation 4 below

procession

.

&Quot; (4) "

에 하기의 수학식 5와 같이 SVD 기반의 블록 대각화 방법을 적용한다.The base station may use a matrix to determine a first pre-

The block diagonalization method based on SVD is applied as shown in Equation (5) below.

&Quot; (5) "

는

Unitary Matrix이고,

는

대각 행렬로 내림차순으로 정렬되며,

는

Unitary Matrix이다.

(제2 파라미터)은

의 처음부터

까지의 열 벡터로 구성되는 행렬이고,

는

의 마지막

열 벡터로 구성되는 행렬이다. here

The

Unitary Matrix,

The

Are arranged in descending order by a diagonal matrix,

The

Unitary Matrix.

(Second parameter)

From the beginning of

Lt; RTI ID = 0.0 > 1, < / RTI >

The

The end of

And a column vector.

는 하기의 수학식 6과 같이 표현된다.The first pre-coding matrix of the k < th > terminal considering the ZF transmitter of the base station

Is expressed by Equation (6) below.

&Quot; (6) "

는

행렬로 diag(

,

,

,

, 0,

, 0)의 값을 가지고,

은 k번째 단말의 n번째 데이터 스트림에 할당되는 전력을 나타낸다. 수학식 6을 수학식 1에 대입하면 기지국의 ZF 송신기를 고려한 제1 사전부호화코드를 결정하는 수학식은 하기의 수학식 7과 같이 정의된다.At this time

The

The matrix diag (

,

,

,

, 0,

, 0), < / RTI >

Represents the power allocated to the n-th data stream of the k-th terminal. When Equation (6) is substituted into Equation (1), the equation for determining the first pre-coding code considering the ZF transmitter of the base station is defined as Equation (7) below.

&Quot; (7) "

와

는 대각 행렬이고,

는 0이 아닌 원소를 Ns개 포함하고 있으므로, 수학식 7의 목적식은 KNs개의 독립적인 채널로 분리된다. 또한, 수학식 7의 제약식은 KNs개의 채널에 할당된 전체 전력에 대한 제약을 나타낸다. 따라서, 수학식 7의 최적해는 워터필링 알고리즘을 이용해서 결정할 수 있다.The base station determines in step 303 the optimal solution of the equation for determining the first pre-coded code using the water filling algorithm. In Equation (7)

Wow

Is a diagonal matrix,

Includes Ns non-zero elements, the objective expression of Equation (7) is separated into KNs independent channels. Also, the constraint of Equation (7) represents the constraint on the total power allocated to the KNs channels. Hence, the optimal solution of Equation (7) can be determined using a water filling algorithm.

를 수학식 6에 대입해서 전체 전송 전력 제약을 만족하는 제1 사전부호화코드를 결정한다.The base station determines in step 304 that the optimal solution < RTI ID = 0.0 >

Into Equation 6 to determine a first pre-coded code that satisfies the total transmission power constraint.

4 is a diagram illustrating a method for determining a second pre-encoder according to an embodiment of the present disclosure.

Referring to FIG. 4, in step 401, the BS decomposes the first pre-coding matrix determined under the total transmission power constraint to generate a reference matrix of a second precoded code.

First, a first pre-coding code satisfying the total transmission power constraint is expressed by Equation (8) below.

&Quot; (8) "

는 수학식 3에서 설명한 바와 같이 하향링크 채널로부터 계산되고, B_k는 L x Ns행렬로

로 정의된다.

과 B_k는 안테나 별 전송 전력 제약하에서 제2 사전부호화코드를 결정하기 위한 기준 행렬로 사용된다.At this time,

Is calculated from the downlink channel as described in Equation (3), and B _k is an L x Ns matrix

.

And B _k are used as reference matrices for determining a second pre-coded code under an antenna-specific transmission power constraint.

In step 402, the base station defines a second pre-coded code mathematical expression considering transmission power constraints for each antenna. When the base station uses the ZF transmitter, the following formula (9) is used to maximize the sum rate of all terminals.

&Quot; (9) "

로 표현되고,

을 만족한다. 또한, N x N 행렬 A에 대해 diag(A)는 행렬 A의 대각 원소로 구성되는 N x 1 벡터를 나타낸다. 이 때, 수학식 9의 목적식은 단말의 합산 전송률을 나타내고, 첫 번째 제약식은 안테나 별 전송 전력 제약을 의미하며, 두 번째 제약식은 단말 간 간섭이 0이 되도록 하기 위한 ZF 전송 조건을 나타낸다.a maximum transmission power of n th antenna when said P _n, P _n is a vector representing the specific transmission antenna power constraint

Lt; / RTI >

. Also, for N x N matrix A , diag ( A ) represents an N x 1 vector consisting of the diagonal elements of matrix A. In this case, the objective equation of Equation (9) represents the aggregate data rate of the UE, the first constraint expresses the transmit power constraint for each antenna, and the second constraint expresses the ZF transmission condition for the inter-terminal interference to be zero.

In step 403, the base station transforms the matrices defined in equation (9) into matrices that determine the precoding matrix closest to the second precoded code reference matrix generated in step 401. [ Specifically, the BS defines a second pre-coding code satisfying the transmission power constraint for each antenna considering the ZF transmitter as Equation (10).

&Quot; (10) "

At this time, A _k denotes a L x N _s complex matrix, and is a matrix that must be determined in order to define a second pre-coded code. The base station transforms the mathematical expression defined by equation (9) into a mathematical expression for finding a matrix closest to the first pre-coding code W _{S, k} under the total transmission power constraint among the second precoding codes W _k satisfying the transmission power constraint for each antenna do. When the distance between the matrix W _k and W _{S, k} is measured on the basis of the MSE, the equation for determining the matrix W _k closest to W _{S, k} is defined by Equation 11 as follows.

&Quot; (11) "

The base station determines in step 404 a second pre-coding code that satisfies the per-antenna transmission power constraint.

Specifically, the base station transforms the equation into a dual optimization mathematical expression by applying the Langrange technique to Equation (11) to reduce the computational amount of Equation (11). The equation (11) converted into the dual optimization mathematical expression is defined by Equation (12) as follows.

&Quot; (12) "

은 Lagrange Multiplier로서 최적화가 필요한 변수를 의미한다. 또한, N_t x N_t 대각 행렬

로 주어진다.At this time,

Is a Lagrange Multiplier which means a variable that needs optimization. Also, N _t x N _t diagonal matrix

.

을 효율적으로 구할 수 있다. Since Equation (11) is the Convex optimization equation, the optimal values of Equations (11) and (12) are the same. In the case of Equation (12), N _t is the number of variables required to be optimized, and since the constraint is simple, optimal

Can be efficiently obtained.

을 이용해서 안테나 별 전송 전력 제약을 만족하는 제2 사전부호화코드를 결정한다. 제2 사전부호화코드를 결정하는 수학식 13은 하기와 같다.The base station calculates the optimal

And determines a second pre-coding code that satisfies the transmission power constraint for each antenna by using the second pre-coding code. Equation (13) for determining the second pre-coded code is as follows.

&Quot; (13) "

5 is a diagram showing a method of precoding a transmission symbol on the basis of a second pre-coded code according to the embodiment of the present disclosure.

Referring to FIG. 5, when data to be transmitted to each terminal is determined, the base station generates a transmission symbol for each terminal through channel coding and modulation considering the downlink channel quality of each terminal in step 501.

That is, the base station symbol-modulates data to generate a transmission symbol.

In step 502, the BS performs S / P conversion on the transmission symbols for each UE in consideration of the number of data streams that can be simultaneously transmitted through the downlink channel, thereby generating a transmission symbol vector for each UE.

The transmission symbol vector b _k is represented by N _{s, k} x 1 vectors. N _{s, k} denotes the number of transmission symbols simultaneously transmitted to the terminal k.

In step 503, the base station applies a second pre-coding code to the transmission symbol vector for each terminal. At this time, the base station applies the second pre-coding code determined for each terminal to the transmission symbol vector for each terminal. Further, the base station generates a final transmission symbol vector by adding the transmission symbol vectors for each terminal to which the second pre-coding code is applied.

&Quot; (14) "

The final transmission symbol vector x is given by N _t x 1 vector.

In step 504, the base station transmits the transmission signal corresponding to each element of the final transmission symbol vector x to the respective terminals through the N _t antennas after passing through the amplifiers. Each terminal detects a transmission symbol vector b _k and a data bit transmitted to the corresponding terminal using signals received from N _r antennas through a downlink channel.

6 is a diagram showing a configuration of a base station according to an embodiment of the present disclosure. For convenience of description, components and components not directly related to the present disclosure will not be shown and described.

Referring to FIG. 6, the base station 100 includes a transceiver 110 and a controller 120.

The transmission / reception unit 110 acquires downlink channel information for each terminal. Also, a transmission signal corresponding to each element of the final symbol vector pre-coded based on the second pre-coded code is transmitted to each terminal.

The transceiver 110 may include a ZF transmitter.

The control unit 120 determines a first pre-coding code based on the acquired downlink channel information and the total transmission power constraint. In addition, the control unit 120 determines the second pre-encoding code based on the first pre-encoding code and the transmit power limitation for each antenna, and pre-encodes the transmit symbol vector based on the second pre-encoding code. At this time, the controller 120 pre-encodes the transmission symbol vector to generate a final symbol vector.

7 is a diagram showing a configuration of a terminal according to an embodiment of the present disclosure. For convenience of description, components and components not directly related to the present disclosure will not be shown and described.

The terminal 200 includes a transceiver 210 and a controller 220.

The transmission / reception unit 210 may transmit the downlink channel information to the base station. The transceiver 210 also receives a transmission signal corresponding to each element of the final symbol vector pre-coded by the base station.

The control unit 220 restores the data stream based on the received transmission signal.

Various embodiments of the present disclosure may in particular be embodied as computer readable code in a computer readable recording medium. The computer readable recording medium is any data storage device capable of storing data that can be read by a computer system. Examples of computer readable recording media include read only memory (ROM), random access memory (RAM), compact disk-read only memory (CD-ROMs), magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission over the Internet) . The computer readable recording medium may also be distributed over networked computer systems, and thus the computer readable code is stored and executed in a distributed manner. In addition, functional programs, code, and code segments for accomplishing the various embodiments of the present disclosure may be readily interpreted by those skilled in the art to which the embodiments of the present disclosure apply.

It will also be appreciated that the apparatus and method according to various embodiments of the present disclosure may be implemented in hardware, software, or a combination of hardware and software. Such software may be, for example, a volatile or nonvolatile storage device such as a storage device such as ROM, whether removable or rewritable, or a memory such as, for example, a RAM, memory chip, For example, a storage medium readable by a machine (e.g., a computer), such as a compact disk (CD), a DVD, a magnetic disk, or a magnetic tape. The method according to various embodiments of the present disclosure may be implemented by a computer or a mobile terminal including a controller and a memory, which memory stores programs or programs containing instructions embodying the embodiments of the present disclosure It will be appreciated that this is an example of a suitable machine readable storage medium.

Accordingly, embodiments of the present disclosure include a program including code for implementing the apparatus or method recited in the claims, and a storage medium readable by a machine (such as a computer) for storing such a program. In addition, such a program may be electronically transported through any medium, such as a communication signal carried over a wired or wireless connection, and embodiments of the present disclosure suitably include equivalents thereof

Also, an apparatus according to various embodiments of the present disclosure may receive and store a program from a program providing apparatus connected by wire or wirelessly. The program providing apparatus includes a memory for storing a program including instructions for causing the program processing apparatus to perform a predetermined content protection method, information necessary for the content protection method, and the like, and a program for executing a wired or wireless communication with the graphics processing apparatus A communication unit, and a control unit for requesting the graphic processing apparatus or automatically transmitting the program to the transmission / reception apparatus.

The embodiments of the present disclosure disclosed in this specification and drawings are merely illustrative of specific examples and are not intended to limit the scope of the present disclosure. It is also to be understood that the embodiments according to the present disclosure described above are merely illustrative and that those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of protection according to the present disclosure should be determined by the following claims.

Various embodiments of the present disclosure may in particular be embodied as computer readable code in a computer readable recording medium. The computer readable recording medium is any data storage device capable of storing data that can be read by a computer system. Examples of computer readable recording media include read only memory (ROM), random access memory (RAM), compact disk-read only memory : CD-ROMs), magnetic tapes, floppy disks, optical data storage devices, and carrier waves (such as data transmission over the Internet) can do. The computer readable recording medium may also be distributed over networked computer systems, and thus the computer readable code is stored and executed in a distributed manner. In addition, functional programs, code, and code segments for accomplishing the various embodiments of the present disclosure may be readily interpreted by those skilled in the art to which the embodiments of the present disclosure apply.

It will also be appreciated that the apparatus and method according to various embodiments of the present disclosure may be implemented in hardware, software, or a combination of hardware and software. Such software may be, for example, a volatile or nonvolatile storage device such as a storage device such as ROM, whether removable or rewritable, or a memory such as, for example, a RAM, memory chip, For example, a storage medium readable by a machine (e.g., a computer), such as a compact disk (CD), a DVD, a magnetic disk, or a magnetic tape. The method according to various embodiments of the present disclosure may be implemented by a computer or a mobile terminal including a controller and a memory, which memory stores programs or programs containing instructions embodying the embodiments of the present disclosure It will be appreciated that this is an example of a suitable machine readable storage medium.

Accordingly, embodiments of the present disclosure include a program including code for implementing the apparatus or method recited in the claims, and a storage medium readable by a machine (such as a computer) for storing such a program. In addition, such a program may be electronically transported through any medium, such as a communication signal carried over a wired or wireless connection, and embodiments of the present disclosure suitably include equivalents thereof

Also, an apparatus according to various embodiments of the present disclosure may receive and store a program from a program providing apparatus connected by wire or wirelessly. The program providing apparatus includes a memory for storing a program including instructions for causing the program processing apparatus to perform a predetermined content protection method, information necessary for the content protection method, and the like, and a program for executing a wired or wireless communication with the graphics processing apparatus A communication unit, and a control unit for requesting the graphic processing apparatus or automatically transmitting the program to the transmission / reception apparatus.

The embodiments of the present disclosure disclosed in this specification and drawings are merely illustrative of specific examples and are not intended to limit the scope of the present disclosure. It is also to be understood that the embodiments according to the present disclosure described above are merely illustrative and that those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of protection according to the present disclosure should be determined by the following claims.

Claims (12)

A method for downlink transmission by a first device having a plurality of antennas,
The method comprising: acquiring downlink channel information for each of a plurality of second devices having a plurality of antennas;
Determining a first pre-coding matrix such that a sum of data rates of the plurality of second devices is maximized considering a constraint condition on the total transmission power of the first device based on the downlink channel information;
Encoding matrixes of the plurality of antennas of the first device and obtaining the reference matrix for the second pre-coding matrix based on the first pre-coding matrix, Determining a pre-coding matrix closest to the reference matrix as a second pre-coding matrix;
And transmitting the data stream using the second pre-coding matrix.
The method according to claim 1,
Wherein the constraint on the total transmission power is a constraint such that the sum of power by the plurality of antennas of the first device is less than a predetermined transmission power.
The method according to claim 1,
Wherein the constraint on the transmit power of each of the plurality of antennas of the first device is a constraint that causes the transmit power in each of the plurality of antennas of the first device to be less than a predetermined transmit power. The method according to claim 1,
Wherein the step of determining the first pre-
Defining a first equation for calculating a summation rate for each of the plurality of second devices satisfying a constraint on the total transmission power;
Applying a block diagonalization method based on a singular value decomposition (SVD) to an interference channel of each of the plurality of second devices;
Applying the SVD-based block diagonalization method to an effective channel of each of the plurality of second devices;
The first parameter calculated in applying the SVD-based block diagonalization method to the interference channel of each of the plurality of second devices, the SVD-based block diagonalization method to the effective channel of each of the plurality of second devices Coding matrix based on a second parameter calculated in the applying step, a constraint on the total transmission power, and the first equation,
The first equation is defined as follows,

Here, W _k Where W _k is an M x L complex matrix, H _k is an N x M uplink channel matrix of a terminal k, I _N is an N x N unit matrix,

Is the variance of the noise, P _sum is the maximum transmission power, M is the number of antennas of the first device, N represents the number of antennas of the second device,
The first parameter

Lt; / RTI >

The

Lt; RTI ID = 0.0 > L < / RTI >

And the second parameter is a null space of

Lt; / RTI >

silver

From the beginning of

Wherein the matrix is a matrix of column vectors.
The method according to claim 1,
Wherein the step of determining the second pre-
Generating a reference matrix for the second pre-coding matrix based on the first pre-coding matrix;
Defining a second equation for calculating a summation rate for each of the plurality of second devices satisfying a constraint on transmit power in each of a plurality of antennas of the first device;
And determining the second pre-encoding matrix based on the reference matrix, the second equation, and a constraint on transmit power in each of the plurality of antennas of the first device,
The second equation is defined as follows,

Herein, when the maximum transmission power of the _nth antenna of the first device is Pn,

Is a vector representing a transmit power constraint for each antenna, and P _n

, Diag ( A ) is an N x 1 vector consisting of diagonal elements of an N x N matrix A.
delete In a first device having a plurality of antennas,
A transmitting and receiving unit for acquiring downlink channel information for each of the plurality of second devices having the plurality of antennas,
Determining a first pre-coding matrix such that a sum of data rates of the plurality of second devices is maximized in consideration of a constraint condition on the total transmission power of the first device based on the downlink channel information,
Acquiring a reference matrix for a second pre-coding matrix based on the first pre-coding matrix, and obtaining a reference matrix for the acquired one of the user-selected coding matrices based on a constraint on transmission power in each of the plurality of antennas of the first device Determining a second pre-coding matrix as a pre-coding matrix closest to the reference matrix,
And a controller for controlling the transceiver to transmit the data stream using the second pre-coding matrix.
8. The method of claim 7,
Wherein the constraint condition for the total transmission power is that the sum of power by the plurality of antennas of the first device is less than a predetermined transmission power.
8. The method of claim 7,
Wherein constraints on the transmit power of each of the plurality of antennas of the first device are constraints such that the transmit power at each of the plurality of antennas of the first device is less than or equal to a predetermined transmit power.
8. The method of claim 7,
Wherein the controller defines a first equation for calculating a summation rate for each of the plurality of second devices satisfying the constraint on the total transmission power,
Applying a SVD (Singular Value Decomposition) based block diagonalization method to an interference channel of each of the plurality of second devices,
Applying the SVD-based block diagonalization method to an effective channel of each of the plurality of second devices,
The first parameter calculated in applying the SVD-based block diagonalization method to the interference channel of each of the plurality of second devices, the SVD-based block diagonalization method to the effective channel of each of the plurality of second devices Determining a first pre-coding matrix based on a second parameter calculated in the applying step, a constraint on the total transmission power, and the first equation,
The first equation is defined as follows,

Here, W _k Where W _k is an M x L complex matrix, H _k is an N x M uplink channel matrix of a terminal k, I _N is an N x N unit matrix,

Is the variance of the noise, P _sum is the maximum transmission power, M is the number of antennas of the first device, N represents the number of antennas of the second device,
The first parameter

Lt; / RTI >

The

Lt; RTI ID = 0.0 > L < / RTI >

(Null Space)
The second parameter

Lt; / RTI >

silver

From the beginning of

Wherein the first matrix is a matrix composed of column vectors up to a first column.
8. The method of claim 7,
Wherein the controller generates a reference matrix for the second pre-encoding matrix based on the first pre-encoding matrix,
Defining a second equation for calculating a summation rate for each of the plurality of second devices satisfying a constraint on transmit power in each of a plurality of antennas of the first device,
Determining the second pre-encoding matrix based on the reference matrix, the second equation and the constraint on transmit power in each of the plurality of antennas of the first device,
The second equation is defined as follows,

Herein, when the maximum transmission power of the _nth antenna of the first device is Pn,

Is a vector representing a transmit power constraint for each antenna, and P _n

It satisfies the first device, characterized in that diag (A) is a N x 1 vector consisting of the diagonal elements of N x N matrix A. delete

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