KR101645416B1 - System and method for interferecne cancellation in multicell multiuser environment - Google Patents

Abstract

The present invention discloses an interference cancellation system and method in a multi-cell multi-user environment. That is, in order to simultaneously solve the interference problem between the intra-cell and the inter-cell in the uplink environment IMAC (interfering multiple access channel) and the downlink environment IBC (interfering broadcasting channel) (Interference Alignment) technique. Also, prior to applying the above technique, self-configuration is performed using the conditional formula for interference alignment, and then self-optimization of the interference is performed through the interference alignment algorithm to solve the inner cell and outer cell interference problem simultaneously Thereby improving the reception performance of the user at the edge of the cell.

Description

[0001] SYSTEM AND METHOD FOR INTERFERENCE CALCULATION IN MULTICELL MULTIUSER ENVIRONMENT [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for eliminating interference in a multi-cell environment of a mobile communication network, and more particularly, to a method for forming a SON (Self-Organizing Network) between distributed nodes in a multi- The present invention relates to an interference cancellation system and a method thereof in a multi-cell multi-user environment for simultaneously reducing inter-cell interference and intra-cell interference.

From the early stages of cellular mobile communication, which is the conceptual step of dividing communication coverage into cells, to the current stage of the introduction of next generation 4G systems, interference problems are emerging as the most important issue among various technical problems.

Conventional cellular systems have managed this interference problem with centralized control, but as the femtocell and next generation 4G systems are introduced, the network structure of the mobile communication system changes into a multi-layer structure, and the number of objects to be managed by the system And it became an environment in which centralized management became impossible at the source.

In this regard, studies on existing interference problems are mainly based on multiuser interference in an environment where a single cell multiuser is present in one cell, or in a multi-cell single user environment, Has been focused on research on external interference problems.

Recently, an interference alignment technique has been proposed to solve the external interference problem in a multi - cell single user environment. Distributed interference alignment algorithms and conditional formulas for interference alignment have been proposed.

However, when the internal cell and the external cell interference problem are simultaneously considered in a multi-cell multiuser system, which is a practical cellular system environment, there is a problem that the interference alignment condition formula and the interference sorting algorithm used in the existing environment can not be applied as they are .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide an intra-cell (IMC) scheme, which is generated in an interfering multiple access channel (IMAC) ) And a method for inter-cell interference in a multi-cell multi-user environment for simultaneously solving the problem of inter-cell interference through self-organizing and self-optimizing processes of SON (Self-Organizing Network) .

According to an aspect of the present invention, there is provided an interference cancellation system in a multi-cell multi-user environment, the system including: a plurality of base stations, each located in a plurality of cell areas, A user terminal for transmitting and receiving data; And exchanges channel information with a neighboring base station through a setup for a designated parameter satisfying a predetermined first conditional formula in each cell region in which the plurality of user terminals are located, And a base station for calculating a predetermined parameter satisfying a predetermined second conditional formula to reduce interference to each of a plurality of cell regions and user terminals on the network and feeding back the calculated parameters to the user terminal.

According to another aspect of the present invention, there is provided a base station that transmits and receives data to and from a plurality of user terminals located in a cell region, the base station comprising: a base station configured to transmit a predetermined parameter satisfying a predetermined first conditional formula A self configuring unit for establishing a network with neighboring base stations and exchanging channel information through setting of the channel configuration; And a self-optimizing unit for calculating a predetermined parameter satisfying a predetermined second conditional formula to reduce interference to each of a plurality of cell areas and a user terminal on the network based on the channel information, .

Preferably, the self-configuring unit is configured to select one of the plurality of user terminals in an interfering multiple access channel (IMAC) and an interfering broadcast channel (IBC) 1 < / RTI > conditional expression is set.

Preferably, the self-configuring unit is configured to set the designated parameter including the number of transmitting-end antennas, the number of receiving-end antennas, and the data stream satisfying the first conditional formula predetermined to determine whether interference can be aligned do.

Preferably, the self-optimizing unit optimizes the second conditional expression in an interfering multiple access channel (IMAC) and an interfering broadcasting channel (IBC) for a plurality of cell regions and user terminals on the network, And calculates the specified parameter satisfying the condition.

Preferably, the self-optimizing unit selects a temporary parameter satisfying a set value for each of a plurality of cell regions and a user terminal on the network, updates the selected temporary parameter until the second conditional expression is satisfied, And a parameter is calculated.

Preferably, the self-optimizing unit includes a precoding matrix for simultaneously aligning intra-cell interference and inter-cell interference for a plurality of cell regions and user terminals on the network, and spatial information for interference alignment, And the parameter is calculated.

According to another aspect of the present invention, there is provided an interference cancellation method in a multi-cell multi-user environment, comprising: setting a designated parameter satisfying a predetermined first conditional formula in a cell region in which a plurality of user terminals are located, A network forming step of forming a network with a base station; A channel information receiving step of receiving channel information on the formed network; A parameter calculating step of calculating a designated parameter satisfying a predetermined second conditional expression to reduce interference to a plurality of cell areas and user terminals on the network based on the received channel information; And an information feedback step of feeding back the calculated parameters to the user terminal.

Advantageously, the network forming step comprises the steps of: setting a predetermined number of cells in an interfering multiple access channel (IMAC) and an interfering broadcast channel (IBC) of each cell area in which a plurality of user terminals are located, 1 < / RTI > conditional expression is set.

Preferably, the network forming step sets the designated parameter including the number of transmitting-end antennas, the number of receiving-end antennas, and the data stream satisfying the predetermined first conditional expression to determine whether or not the interference can be aligned. do.

Preferably, the parameter calculation step may include calculating a second conditional expression (i) in an interfering multiple access channel (IMAC) and an interfering broadcasting channel (IBC) for each of a plurality of cell regions and a user terminal on the network, Of the specified parameter.

Preferably, the parameter calculating step may include: a parameter selecting step of selecting a temporary parameter satisfying a set value for each of a plurality of cell areas and a user terminal on the network; And a parameter updating step of updating the selected temporary parameter until the second conditional expression is satisfied and calculating the temporary parameter as the designated parameter.

Preferably, the parameter calculation step may include a precoding matrix for simultaneously aligning intra-cell interference and inter-cell interference for each of a plurality of cell regions and user terminals on the network, and spatial information for interference alignment, And the set parameter is calculated.

According to the interference cancellation system and the method thereof in the multi-cell multi-user environment according to the present invention, interference cancellation can be performed in an IMAC (Interfering Multiple Access Channel) environment and an IBC (Interfering Broadcast Channel) The distributed nodes can perform the self-organizing process by providing the interference alignment condition expression that determines whether or not the node can be made available. Also, by performing the self-optimization process on the interference through the interference sorting algorithm, it is possible to simultaneously solve the internal cell and the external cell interference problem, thereby improving the reception performance of the user at the edge of the cell.

FIG. 1 is a schematic configuration diagram of an interference cancellation system in a multi-cell multi-user environment according to an embodiment of the present invention; FIG.
2 is a configuration diagram illustrating a downlink environment (IBC) of a multi-cell multi-user system according to an embodiment of the present invention;
3 is a block diagram illustrating an interfering multiple access channel (IMAC) of a multi-cell multi-user system according to an embodiment of the present invention;
FIG. 4 is a configuration diagram of an analysis of Equation (4) according to an embodiment of the present invention;
5 is a schematic configuration diagram of a base station according to an embodiment of the present invention;
6 to 8 are diagrams for explaining an actual application example of a self-configuration and a self-optimization operation of a base station according to an embodiment of the present invention.
9 is a schematic configuration diagram of an interference cancellation system in a multi-cell multi-user environment according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram of an interference cancellation system in a multi-cell multi-user environment according to an embodiment of the present invention.

As shown in FIG. 1, the system includes a user terminal 100, which is located in each of a plurality of cell areas and transmits and receives data to and from neighboring base stations on a cell area where the user terminals 100 are located, Cell interference and intra-cell interference on the basis of a predetermined conditional expression in a multicell multi-user environment, as shown in FIG. Herein, the multi-cell multiuser environment refers to an environment in which a plurality of user terminals 100 are located in each cell in a multi-cell base in which a macro cell and a femto cell coexist In such a multi-cell multi-user environment, inter-cell interference corresponding to macrocell interferences, femtocell interferences, and interference between macrocells and femtocells, intercell interference, Intra-cell interference corresponding to the interference may exist.

Further, such a multi-cell multi-user environment can be divided into an interfering broadcasting channel (IBC) and an interfering multiple access channel (IMAC).

First, referring to FIG. 2, an interfering broadcast channel (IBC) will be described below.

개의 셀이 존재하고 각 셀마다

개의 사용자단말기(100)가 있는 IBC 시스템을 도시하고 있다. 상황에 따라 각 셀은 마크로 셀이나 펨토 셀 혹은 이들의 조합으로 구성될 수 있다. 본 발명에서는 설명의 편의를 위하여 각 셀마다

가 동일하다고 가정함으로 각 셀의 사용자단말기(100)를

로 나타낸다.2

Cells exist and each cell

Lt; RTI ID = 0.0 > IBC < / RTI > Depending on the situation, each cell may be composed of a macrocell, a femtocell or a combination thereof. In the present invention, for convenience of explanation,

Are assumed to be the same, the user terminal 100 of each cell

Respectively.

번째 셀의

번째 사용자단말기(100)의 수신신호를 일반적인 수식으로 나타내면 아래의 [수학식 1]과 같다.In this regard,

Th cell

The reception signal of the i < th > user terminal 100 may be represented by the following general expression.

[Equation 1]

와

로 나타낸다. [수학식 1]에서

는 t번째 기지국(200)과 g번째 셀의 k번째 사용자단말기(100) 사이의

채널 매트릭스를 나타내고,

는 g번째 셀의 k번째 사용자단말기(100)를 위해 사용되는

프리코딩 행렬을 나타내며,

는 g번째 기지국(200)이 g번째 셀의 k번째 사용자단말기(100)로 전송하는

전송신호 벡터를 나타낸다. 여기서

는 각 송신단에서 접속한 사용자단말기(100)에게 전송하고자 하는 데이터스트림수이다. 그리고

는 g번째 셀의 k번째 사용자단말기(100)에 해당하는

크기의 백색 가우시안 잡음 벡터를 나타내며, N(0,1)과 같은 분포를 따른다.In this system, the number of antennas of the base station 200, which is the transmitting end, and the number of antennas of the user terminal 100, which is the receiving end,

Wow

Respectively. In Equation (1)

(K) between the t-th base station 200 and the k-th user terminal 100 of the g- th cell

Channel matrix,

Is used for the k < th > user terminal 100 of the g < th &

≪ / RTI > represents a precoding matrix,

Is transmitted from the g < th > base station 200 to the k < th > user terminal 100 of the g &

Represents a transmission signal vector. here

Is the number of data streams to be transmitted to the user terminal 100 connected at each transmitting end. And

Corresponding to the k < th > user terminal 100 of the g < th &

, And follows a distribution such as N (0, 1).

Next, referring to FIG. 3, an uplink environment (IMAC) will be described as follows.

개의 셀이 존재하고 각 셀마다

개의 사용자단말기(100)가 있는 IMAC 시스템을 도시하고 있다.3,

Cells exist and each cell

Lt; RTI ID = 0.0 > 100 < / RTI >

In this regard, the signal received from the t-th user terminal 100 in the cell of the g-th base station 200 can be generally expressed as shown in Equation (2) below.

&Quot; (2) "

와

로 나타낸다. [수학식 2]에서

는 t번째 셀의 l번째 사용자단말기(100)와 g번째 기지국(200) 사이의

채널 매트릭스를 나타내고,

는 g번째 셀의 k번째 사용자단말기(100)가 사용하는

프리코딩 행렬을 나타내며

는 g번째 셀의 k번째 사용자단말기(100)가 전송하는

전송신호 벡터를 나타낸다. 여기서,

는 사용자단말기(100)가 기지국(200)으로 전송하고자 하는 데이터스트림수이다.

는 g번째 기지국(200)에서 발생하는

크기의 백색 가우시안 잡음 벡터를 나타내며, N(0,1)과 같은 분포를 따른다.In this system, the number of antennas of the user terminal 100 and the number of antennas of the base station 200,

Wow

Respectively. In Equation (2)

Th user terminal 100 and the g < th > base station 200 of the t <

Channel matrix,

Is used by the k-th user terminal 100 of the g-th cell

Represents a precoding matrix

(K) th user terminal 100 of the g < th >

Represents a transmission signal vector. here,

Is the number of data streams that the user terminal 100 wants to transmit to the base station 200.

Is transmitted from the g < th >

, And follows a distribution such as N (0, 1).

The base station 200 performs setting for a designated parameter satisfying a preset conditional formula for interference through interference sorting in the multi-cell multi-user environment to form a network with neighboring base stations and exchange channel information Self-configuration, i.e., self-configuration. More specifically, in order to remove interference through an interference sorting algorithm in a multi-cell multi-user environment, the base station 200 must first determine whether the multi-cell multi-user system satisfies the conditions for interference sorting. Therefore, by considering the multi-cell multi-user system as a quadratic linear equation system and comparing the equation of the system with the number of unknowns, it is confirmed whether there is a solution of the system, that is, interference can be eliminated through an interference sorting algorithm. The conditional expression for this interference alignment enables a network to be formed between adjacent nodes for interference alignment.

와 수신단필터 행렬

이 존재한다면 셀 내부 간섭 및 셀간의 간섭정렬이 가능하다. That is, in a multi-cell multi-user IBC environment, a precoding matrix satisfying the following equations (3) and (4)

And a receiver filter matrix

It is possible to arrange intra-cell interference and inter-cell interference.

&Quot; (3) "

&Quot; (4) "

가 되게 하는

,

가 있다면 간섭정렬이 가능하다. 따라서 [수학식 3]과 [수학식 4]를 동시에 고려하여 다중 셀 다중 사용자 환경에서 상기 두 식을 만족하는 해 (

,

)가 있을 조건을 구해야 한다.Here, it is assumed that the components of all channel matrices are iid (independent and identically distributed). Also, Equation (3) is interference between the inner cell and the outer cell. These interference components are all eliminated by the condition of Equation (3), and the rank of the magnetic signal components satisfying Equation (4) becomes the number of data streams

To become

,

Interference alignment is possible. Therefore, considering both [Equation 3] and [Equation 4], a solution satisfying the above two equations in a multi-

,

) Should be sought.

In order to calculate the number of equations and the number of unknowns generated by simultaneously considering Equations (3) and (4), Equations (3) and (4) .

&Quot; (5) "

는 각각 프리코딩 행렬

와 수신단 필터행렬

의 열벡터이다. 이와 관련하여 상기 [수학식 5]를 통해 필요한 방정식의 수는 하기 [수학식 6]과 같이 나타낼 수 있다.In the above equation (5)

Respectively,

And a receiver filter matrix

. In this regard, the number of necessary equations through Equation (5) can be expressed as Equation (6) below.

&Quot; (6) "

와

은 각각 [수학식 3]과 [수학식 4]를 만족하는 행렬

와

의 열수를 나타낸다.On the other hand, in Equation (5)

Wow

Are matrices satisfying the equations (3) and (4), respectively,

Wow

.

와

에서 필요한 최소한의 미지수 수는 각각

와

이다. 따라서 전체적으로 필요한 미지수의 수는 아래의 [수학식 7]과 같이 나타낼 수 있다.Next, the number of unknowns that satisfy the equations (3) and (4) will be examined. One matrix

Wow

The minimum number of unknowns required in

Wow

to be. Therefore, the number of unknowns required as a whole can be expressed by Equation (7) below.

&Quot; (7) "

는 전송단 안테나수로서 IBC환경에서는

로, IMAC 환경에서는

로 나타낼 수 있다. 또한,

는 수신단 안테나수를 의미하며, IBC환경에서는

로, IMAC 환경에서는

로 나타낼 수 있다. 다중 셀 다중 사용자 시스템에서 간섭정렬을 위한 해가 존재하려면 상기 시스템에서 구한 미지수의 수가 방정식의 수보다 많거나 같아야 한다. 이와 관련하여 아래의 [수학식 8]은 IBC 시스템에서 간섭정렬을 위한 해가 존재할 조건식이다.In Equation (7)

Is the number of transmitting-end antennas. In the IBC environment

In the IMAC environment,

. Also,

Denotes the number of antennas at the receiving end, and in the IBC environment

In the IMAC environment,

. The number of unknowns in the system must be greater than or equal to the number of equations in order to have a solution for interference alignment in a multi-cell multi-user system. Equation (8) below is a conditional expression in which there is a solution for interference alignment in the IBC system.

&Quot; (8) "

In the IMAC system, which is an uplink environment, the same conditional expression as in Equation (8) can be used for interference alignment. Therefore, in order to remove interference through interference sorting in an IBC or IMAC environment of a multi-cell multi-user system, adjacent nodes must form a network satisfying the conditional expression (8).

In the above system, if the number of transmission-end antennas and the number of reception-end antennas are equal to M and N, respectively, and the number of data streams to be transmitted is equal to D, the condition for the system harm is expressed by Equation (9).

&Quot; (9) "

와 간섭을 위한 간섭공간

을 반복적인 알고리즘을 통해 찾는다. 여기서, 업링크 환경인 IMAC과 다운링크 환경인 IBC에서 적용되는 간섭정렬 알고리즘은 동일하다.In addition, when the self-configuration for the multi-cell multi-user environment is completed as described above, the base station 200 calculates a designated parameter satisfying a preset conditional equation based on the channel information received from the formed network, And performs self-optimization to reduce interference to each of a plurality of cell regions and each of the user terminals 100. More specifically, the base station 200 has a G-cell of a repetitive interference sorting algorithm, which is a scheme proposed for inter-cell interference in an interference channel environment in which there are G cells and a single user terminal 100 (K = 1) And is applied to a multi-cell multi-user environment in which K users exist in each cell. In other words, the base station 200 generates a precoding matrix for simultaneously aligning intra-cell interference and intra-cell interference in a multi-

And an interference space

Through the iterative algorithm. Here, the interference alignment algorithm applied in the uplink environment IMAC and the downlink environment IBC are the same.

Equation (10) below is a general expression of an objective function for interference alignment.

&Quot; (10) "

에서

는

로

는

로 설정하여

가 되고, IMAC환경에서

의

는

로

는

로 설정하여

가 된다. 여기서

는 g번째 셀의 k번째 사용자단말기(100)를 위한 간섭정렬 부공간인

에 대한 직교정규한(orthonormal)한 기저를 나타내며,

는 g번째 셀의 k번째 사용자단말기(100) 입장에서 간섭이 되는 채널을 나타낸다. 이때, 간섭이 되는 채널은 셀 내부 간섭과 셀간의 간섭 모두를 포함한 것이다. 따라서 [수학식 10]이 의미하는 바는 간섭성분

을

간섭 공간에 정사영시킨

성분과

성분과의 차이를 최소화하는 것이다. 다시 말해, 간섭정렬의 에러를 최소화하는

와

를 산출함으로써, 이를 통해 도 4에 도시한 바와 같이 간섭성분들을 간섭을 위한 공간인

로 정렬시킨다.In this regard, as shown in Equations (1) and (2), since the interference channel considered in the uplink and the interference channel considered in the downlink should be distinguished from each other,

in

The

in

The

By setting

, And in the IMAC environment

of

The

in

The

By setting

. here

Is the interference alignment subspace for the k < th > user terminal 100 of the g <

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

Represents a channel that is an interference in the position of the kth user terminal 100 in the gth cell. At this time, an interfering channel includes both intra-cell interference and inter-cell interference. Hence, Equation (10) means that the interference component

of

To the interference space

Ingredient

Minimizing the difference between the components. In other words, to minimize errors in interference alignment

Wow

Thereby calculating the interference components as a space for interference, as shown in FIG. 4

.

Hereinafter, a more specific configuration of the base station 200 will be described with reference to FIG. That is, the base station 200 includes a self-configuring unit 210 for performing self-configuration for a multi-cell multi-user environment, and a base station 200 for reducing interference to each of a plurality of cell areas and user terminals 100 on the network And a self-optimizing unit 220 for performing self-optimization.

The autoconfiguration unit 210 performs a setting for a designated parameter satisfying a predetermined conditional formula for interference through interference sorting in a multi-cell multi-user environment to form a network with neighboring base stations to exchange channel information Self-configuration, i.e., self-configuration. More specifically, the self configurator 210 sets parameters such as the number of antennas of the transmitting end, the number of the receiving end antennas, and the number of data streams through the interference alignment condition equation of Equation (8).

&Quot; (8) "

The self configurator 210 forms a network with neighboring base stations and performs self configuration by exchanging channel information between the base stations of the formed network.

(identity matrix)를 만족하는 임의의

프리코딩 행렬

를 모든 셀 t와 사용자 l에 대해서 선택한다. 또한, 자기최적화부(220)는 아래의 [수학식 11]을 통해 모든 셀 g와 사용자 k에 대한

를 계산한다.When the self-configuration for the multi-cell multi-user environment is completed, the self optimizing unit 220 calculates a designated parameter satisfying a predetermined conditional expression based on the channel information received from the formed network, And performs self-optimization to reduce the interference to the user terminal 100 and the user terminal 100, respectively. More specifically, the self optimizing unit 220 eliminates interference in a multi-cell multi-user environment, assuming that all base stations perform a self-optimization process in the downlink and uplink environments. That is, the self-optimizing unit 220

lt; RTI ID = 0.0 > identity matrix

Precoding matrix

Is selected for all cells t and l. In addition, the self-optimizing unit 220 may be configured to optimize for all cells g and k

.

&Quot; (11) "

는 행렬 H의 가장 큰

개의 고유값(eigenvalue)에 해당하는 고유벡터(eigenvectors)를 나타내고

는 행렬 H의 가장 큰

개의 고유값(eigenvalue)에 해당하는 고유벡터(eigenvectors)를 나타낸다.here,

Is the largest of the matrix H

Eigenvectors corresponding to the eigenvalues of eigenvectors

Is the largest of the matrix H

Eigenvectors corresponding to the eigenvalues of eigenvectors.

을 계산한다. On the basis of this, the self-optimizing unit 220 obtains, for all t and l from the following equation (12)

.

&Quot; (12) "

와

를 구하는 과정을 상술한 [수학식 10]의 목적함수가 수렴할 때까지 반복하고, 상기 목적함수가 수렴되면 아래의 [수학식 13]을 통해

로부터 수신단에서 사용되는 필터 행렬

를 산출함으로써, 산출된 프리코딩 행렬을 피트백을 통해 사용자단말기(100)에 전달한다.On the other hand, the self-optimizing unit 220

Wow

Is repeated until the objective function of Equation (10) converges, and when the objective function is converged, the following Equation (13) is obtained

Lt; RTI ID = 0.0 > filter matrix &

And transmits the calculated precoding matrix to the user terminal 100 via feedback.

&Quot; (10) "

&Quot; (13) "

는 간섭을 정렬시킬 공간인

에 직교한 부공간을 나타낸다.here,

Is the space to align the interference

And a subspace orthogonal to the subspace.

For reference, an actual application example of the self-configuration and self-optimizing operation of the base station 200 described above with reference to FIGS. 6 to 8 will be described.

FIG. 6 illustrates an embodiment of a SON (Self-Organizing Network) function through self-configuration and self-optimization in a multi-cell IBC system in which a macrocell and a femtocell coexist.

That is, as shown in FIG. 6, in the multi-cell IBC system, it is assumed that one macrocell and two adjacent femtocells form an SON, and that there are two users in the macrocell and the femtocell, respectively. At this time, each femto base station interferes with a user of a neighboring femtocell and a macrocell user, and the macro base station interferes with neighboring femtocell users. There is also interference within each cell.

FIG. 7 shows a performance graph when an interference sorting algorithm is applied in the same environment as the FIG. 6 embodiment. Here, the horizontal axis of the graph represents transmission power, and the vertical axis represents a sum rate. Also, the slope of the sum rate represents degree of freedom (DoF).

In other words, as shown in FIG. 7, when there are three adjacent cells and two users have two receiving antennas for each cell, when the number of data streams to be transmitted by the base station is one, interference interference The number M of transmit antennas that can be aligned can be expressed as shown in the following Equation (14) from Equation (9).

&Quot; (9) "

&Quot; (14) "

In this case, when the number of transmission antennas satisfies the above formula (14), that is, when each base station uses six transmission antennas, the slope of the sum rate indicates the correct DoF 6, whereas when five transmission antennas are used, By observing DoF, it can be confirmed that the interference alignment is not performed properly.

FIG. 8 shows a performance graph in an environment in which there are two users having two cells and two receiving antennas for each cell. Here, when the number of data streams to be transmitted by the base station is 1, the number of transmission antennas obtained by using the interference alignment equation is 4 or more.

That is, as shown in FIG. 8, when the transmission antenna is 3, a significantly lower DoF is obtained. On the other hand, when the transmission antenna is 4, the inclination of the sum rate is equal to the required DoF 4, It can be seen that it was performed.

As described above, according to the interference cancellation system in the multi-cell multi-user environment according to the present invention, in the interfering multiple access channel (IMAC), which is an uplink environment and the Interfering Broadcasting Channel (IBC) (Interference Alignment) technique to simultaneously solve the interference problem between the cell and the cell. Also, prior to applying the above technique, self-configuration is performed using the conditional formula for interference alignment, and then self-optimization of the interference is performed through the interference alignment algorithm to solve the inner cell and outer cell interference problem simultaneously Thereby improving the reception performance of the user at the edge of the cell.

Hereinafter, an interference cancellation method in a multi-cell multi-user environment according to the present invention will be described with reference to FIG. Here, for convenience of description, the components shown in FIGS. 1 to 8 will be described with reference to corresponding reference numerals.

First, the base station 200 configures a designated parameter satisfying a predetermined conditional formula for interference through interference alignment in a multi-cell multi-user environment to form a network with an adjacent base station (S110). Preferably, the self configuring unit 210 establishes a network with an adjacent base station by performing a setting for a designated parameter satisfying a predetermined conditional formula for interference through interference sorting in a multi-cell multi-user environment. More specifically, the self configurator 210 sets parameters such as the number of antennas of the transmitting end, the number of the receiving end antennas, and the number of data streams through the interference alignment condition equation of Equation (8).

&Quot; (8) "

Then, the base station 200 exchanges channel information (S120). Preferably, the self configuring unit 210 performs self-configuration by exchanging channel information between base stations of the network formed with the self configuring unit 210.

(identity matrix)를 만족하는 임의의

프리코딩 행렬

를 모든 셀 t와 사용자 l에 대해서 선택한다. 또한, 자기최적화부(220)는 아래의 [수학식 11]을 통해 모든 셀 g와 사용자 k에 대한

를 계산한다.Then, the base station 200 selects any parameter for self-optimization (S130-S140). Preferably, the self-optimizing unit 220

lt; RTI ID = 0.0 > identity matrix

Precoding matrix

Is selected for all cells t and l. In addition, the self-optimizing unit 220 may be configured to optimize for all cells g and k

.

&Quot; (11) "

는 행렬 H의 가장 큰

개의 고유값(eigenvalue)에 해당하는 고유벡터(eigenvectors)를 나타내고

는 행렬 H의 가장 큰

개의 고유값(eigenvalue)에 해당하는 고유벡터(eigenvectors)를 나타낸다.here,

Is the largest of the matrix H

Eigenvectors corresponding to the eigenvalues of eigenvectors

Is the largest of the matrix H

Eigenvectors corresponding to the eigenvalues of eigenvectors.

을 계산하고, 이후

와

를 구하는 과정(S140,S150)을 [수학식 10]의 목적함수가 수렴할 때까지 반복한다.Next, the base station 200 calculates the designated parameter for self-optimization and confirms the convergence state of the objective function (S150-S170). Preferably, the self-optimizing unit 220 may be configured to perform a correction on all t, l

And then calculates

Wow

(S140, S150) is repeated until the objective function of Equation (10) converges.

&Quot; (12) "

&Quot; (10) "

로부터 수신단에서 사용되는 필터 행렬

를 산출함으로써, 산출된 프리코딩 행렬을 피트백을 통해 사용자단말기(100)에 전달한다.Then, the base station 100 optimizes the calculated parameters and feeds back the parameters to the user (S180-S190). Preferably, when the objective function is converged, the self-optimizing unit 220 calculates the self-optimization function

Lt; RTI ID = 0.0 > filter matrix &

And transmits the calculated precoding matrix to the user terminal 100 via feedback.

&Quot; (13) "

는 간섭을 정렬시킬 공간인

에 직교한 부공간을 나타낸다.here,

Is the space to align the interference

And a subspace orthogonal to the subspace.

As described above, according to the interference cancellation method in the multi-cell multi-user environment according to the present invention, in the interfering multiple access channel (IMAC) as the uplink environment and the interfering broadcasting channel (IBC) (Interference Alignment) technique to simultaneously solve the interference problem between the cell and the cell. Also, prior to applying the above technique, self-configuration is performed using the conditional formula for interference alignment, and then self-optimization of the interference is performed through the interference alignment algorithm to solve the inner cell and outer cell interference problem simultaneously Thereby improving the reception performance of the user at the edge of the cell.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, 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 by the appended claims.

The interference cancellation system and method in a multi-cell environment according to the present invention can form an SON (Self-Organizing Network) between distributed nodes in a multi-cell multiuser environment, It is possible to reduce the intra-cell interference simultaneously. Therefore, the present invention overcomes the limitations of the prior art, It is an invention that is industrially usable.

100: User terminal
200: base station
210: self configuring unit 220: self optimizing unit

Claims (13)

delete (BS) through a setting for a designated parameter satisfying a first conditional formula set in an uplink environment (IMAC) and an interfering broadcasting channel (IBC) of a cell area in which a plurality of user terminals are located, A self configurator for exchanging channel information by forming a network with the base station; And
And a self-optimizing unit for calculating a predetermined parameter satisfying a predetermined second conditional expression to reduce interference to each of a plurality of cell areas and user terminals on the network based on the channel information, . delete 3. The method of claim 2,
The self-
And sets the designated parameter including the number of transmitting-end antennas, the number of receiving-end antennas, and the number of data streams satisfying the first conditional formula set in advance to determine whether interference can be aligned. 3. The method of claim 2,
Wherein the self-
Calculating the designated parameter satisfying the second conditional expression in an uplink environment (IMAC) and a downlink environment (IBC) for a plurality of cell areas and user terminals on the network Characterized in that the base station. 6. The method of claim 5,
Wherein the self-
Selects a temporary parameter satisfying a set value for each of a plurality of cell regions and a user terminal on the network and updates the selected temporary parameter until the second conditional expression is satisfied to calculate the selected parameter as the designated parameter . The method according to claim 6,
Wherein the self-
For each of a plurality of cell regions and a user terminal on the network, a pre-coding matrix for simultaneously aligning intra-cell interference and extrinsic interference, and spatial parameters for interference alignment. . A predetermined parameter satisfying a first conditional formula set in a cell area in which a plurality of user terminals are located and an interfering multiple access channel (IMAC) and an interfering broadcasting channel (IBC) A network forming step of forming a network;
A channel information receiving step of receiving channel information on the formed network;
A parameter calculating step of calculating a designated parameter satisfying a predetermined second conditional expression to reduce interference to a plurality of cell areas and user terminals on the network based on the received channel information; And
And an information feedback step of feeding back the calculated parameters to the user terminal. delete 9. The method of claim 8,
Wherein the network forming step comprises:
The number of transmitting end antennas, the number of receiving end antennas, and the number of data streams satisfying the first conditional formula set in advance in order to determine whether or not the interference can be aligned. Removal method. 9. The method of claim 8,
Wherein the parameter calculating step comprises:
Calculating the designated parameter satisfying the second conditional expression in an uplink environment (IMAC) and a downlink environment (IBC) for a plurality of cell areas and user terminals on the network A method for eliminating interference in a multi-cell multi-user environment. 12. The method of claim 11,
Wherein the parameter calculating step comprises:
A parameter selection step of selecting a temporary parameter satisfying a set value for each of a plurality of cell areas and user terminals on the network; And
And a parameter updating step of updating the selected temporary parameter until the second conditional expression is satisfied and calculating the updated parameter as the designated parameter. 13. The method of claim 12,
Wherein the parameter calculating step comprises:
For each of a plurality of cell regions and user terminals on the network, a pre-coding matrix for simultaneously aligning intra-cell interference and extrinsic interference, and spatial parameters for interference alignment. A method for interference cancellation in a multi - user cell environment.

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