KR20190089510A - Method and apparatus for controlling interference for uplink and downlink in multi-tier heterogeneous network with in-band wireless backhaul - Google Patents

Abstract

A method and an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul are presented. In an uplink and downlink interference control method of a multi-layer heterogeneous network using an in-band wireless backhaul according to an exemplary embodiment, a wide area cell base station transmits channel information on a network from a small cell base station, a minimum target transmission rate a target rate condition and a power limitation condition; Performing centralized interference control for beam forming and power allocation of the entire network by using channel information in the wide area cell base station; And transmitting the optimized beamforming and power allocation parameters to the corresponding small cell base station. In another embodiment, the multi-layer heterogeneous multi- The uplink and downlink interference control method of the network includes a step of performing a distributed interference control so that each small cell base station optimizes beam forming and power distribution using the location information of the small cell base stations without the help of a wide area cell base station .

Description

TECHNICAL FIELD [0001] The present invention relates to a method and an apparatus for controlling uplink and downlink interference in a multi-layer heterogeneous network using an in-band wireless backhaul, and a method and apparatus for controlling uplink and downlink interference in a multi-

The following embodiments are directed to a method and apparatus for controlling uplink and downlink interference in a multi-layer heterogeneous network, and more particularly, to a technique for controlling uplink and downlink interference for operating an in-band wireless backhaul system in a multi-layer heterogeneous network.

As the demand for small cell network systems increases, the use of wireless backhaul, which is easier to install than a wired backhaul, is getting popular in order to operate a plurality of small cells.

According to the existing technology, it is found that using a two-tier heterogeneous network with a wireless backhaul is superior to the existing single cell system in terms of energy efficiency. Therefore, a multi-layer heterogeneous network using wireless backhaul is required.

A first tier of a two-tier heterogeneous network refers to a wireless backhaul link between one wide area cell base station (MBS) and a plurality of small cell base stations (SBSs) Refers to a link between small cell base stations (SBSs) and user terminals (UEs) allocated to each small cell.

An in-band wireless backhaul where the first and second layers share the same frequency is referred to as an out-of-band wireless backhaul. . On the other hand, interference management of in-band wireless backhaul systems can achieve higher transmission capacity than out-of-band wireless backhaul systems.

Korean Patent Laid-Open No. 10-2012-0007997 relates to a method of controlling interference between a base station and a terminal for extending a small cell coverage, and more particularly, to an interference control of a base station and a terminal for extending a small- And a description of the method.

Korean Patent Laid-Open No. 10-2012-0007997

The present invention relates to a method and an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul, and more particularly, to an in- And provides a technique for controlling an interference signal existing in a backhaul channel and an access channel.

Embodiments utilize Reverse-Time Division Duplex (Reverse-TDD) to control interference factors occurring in a multi-layer heterogeneous network system using an in-band wireless backhaul, And a method and an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul which controls residual interference signals through allocation techniques.

The present invention also provides a decentralized interference control method that each small cell base station can independently perform, as well as a centralized interference control that performs all information in a wide area cell base station.

In contrast to the conventional out-of-band wireless backhaul system, in-band wireless backhaul systems have inter-layer interference, and provide beam forming and power allocation techniques to control the inter-layer interference.

Also, in order to introduce into a real system, the overhead due to information exchange between base stations and the computational complexity must be greatly reduced. For this purpose, a fixed beam forming technique and a fixed power allocation technique of a wide area cell base station are provided.

In an uplink and downlink interference control method of a multi-layer heterogeneous network using an in-band wireless backhaul according to an exemplary embodiment, a wide area cell base station transmits channel information on a network from a small cell base station, a minimum target transmission rate a target rate condition and a power limitation condition; Performing centralized interference control for beam forming and power allocation of the entire network by using channel information in the wide area cell base station; And transmitting the optimized beamforming and power allocation parameters to the corresponding small cell base station, respectively.

And transmitting a power allocation value from the small cell base station to the user terminals of the small cell.

Performing centralized interference control for beam forming and power allocation of the entire network using channel information in the wide area cell base station includes setting a target transmission rate of the wireless backhaul link so as not to be smaller than a transmission rate of the small cell; The method comprising: maximizing a signal-to-interference plus noise ratio (SINR) of a received signal for each link of the wireless backhaul link or updating a beamforming matrix of a wide area cell base station satisfying a predetermined criterion; Updating a power allocation vector of a wide area cell base station that satisfies a target transmission rate of a downlink of the wireless backhaul link to a minimum power; Updating a power allocation vector and a maximum power limitation condition of a user terminal belonging to a small cell that satisfies a target transmission rate of a small cell uplink with a minimum power as much as possible; Updating the beamforming matrix and the maximum power constraint of the small cell base station that maximizes the SINR or satisfies a predetermined criterion; And a step of updating a power allocation vector and a maximum power limitation condition of a small cell base station that satisfies a maximum transmission power of the uplink and the target transmission rate of the small cell downlink of the wireless backhaul link to the minimum power, You can repeat until you are satisfied.

The step of performing centralized interference control for beamforming and power allocation of the entire network using the channel information in the wide area cell base station may include initializing a beamforming matrix of the wide area cell base station and a beamforming matrix of the small cell base station step; And initializing a power allocation vector of the wide area cell base station, a power allocation vector of the small cell base station, a power allocation vector of the user terminal, and the maximum power restriction condition, The beam forming and the power distribution of the cell base station and the small cell base stations can be simultaneously optimized.

The step of performing centralized interference control for beam forming and power allocation of the entire network using the channel information in the wide area cell base station comprises the steps of performing a reverse- Time Division Duplex, and Reverse-TDD), the inter-link interference can be avoided by reversing the direction of the uplink and the downlink in each tier.

Wherein the step of transmitting the optimized beamforming and power allocation parameters to the corresponding small cell base station comprises: determining a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station, And may transmit the variables of the power allocation vector of the user terminals to the small cell base station.

The method of controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul according to another embodiment is characterized in that each small cell base station uses position information of the small cell base stations without the help of a wide- And performing dispersion-based interference control to optimize beamforming and power distribution.

And transmitting power allocation values to the user terminals of the small cell in each of the small cell bases, wherein the beam forming and power distribution of the wide cell base station and the small cell base stations Can be optimized at the same time.

The step of performing dispersion-type interference control to optimize beamforming and power allocation using the location information of the small cell base stations may include: determining a target transmission rate of a small- cell uplink to a user terminal belonging to a small- Updating a power allocation vector; Updating a beamforming matrix of a small cell base station satisfying a predetermined criterion or maximizing a Signal-To-Interference plus Noise Ratio (SINR) of a received signal for each link of a wireless backhaul link; And updating a power allocation vector of the small cell base station that satisfies the maximum transmission power of the uplink and the target data rate of the small cell downlink of the wireless backhaul link to the minimum, have.

And a step of initializing a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station, and a power allocation vector of the user terminal.

A fixed beamforming matrix is designed to obtain a beamforming matrix of a wideband cell base station; And a step of designing a fixed power allocation matrix to obtain a power allocation vector of a wide area cell base station.

The step of performing dispersion-based interference control to optimize beamforming and power allocation using the location information of the small cell base stations may include performing a Reverse-Time-Interference Control operation to enable simultaneous operation in the same band of the multi- The inter-link interference can be avoided by reversing the uplink and downlink directions of each tier using Division Duplex and Reverse-TDD.

In an uplink and downlink interference control apparatus of a multi-layer heterogeneous network using an in-band wireless backhaul according to yet another embodiment, a wide-area cell base station receives channel information on a network from small cell base stations, a minimum target transmission rate an information collector receiving information on a target rate condition and a power limitation condition; An interference controller for performing centralized interference control for beamforming and power allocation of the entire network by using channel information in the wide area cell base station; And a transmitter for delivering optimized beamforming and power allocation parameters to the corresponding small cell base station, wherein the beamforming and power allocation of the wide area cell base station and the small cell base stations to minimize transmission power of the base stations, Can be optimized at the same time.

Wherein the interference control unit initializes a beamforming matrix of the wide area cell base station and a beamforming matrix of the small cell base station and calculates a power allocation vector of the wide area cell base station, a power allocation vector of the small cell base station, An initialization unit for initializing the maximum power limitation condition; A target transmission rate setting unit setting a target transmission rate of the wireless backhaul link so as not to be smaller than a transmission rate of the small cell; (SINR) of a received signal for each link of the wireless backhaul link, or updates a beamforming matrix of a wide area cell base station satisfying a preset criterion, and updates the beamforming matrix of the wireless backhaul link The power allocation vector of the user terminal belonging to the small cell which satisfies the target transmission rate of the small cell uplink at the minimum power as much as possible and the maximum power allocation vector Updating the power constraint condition and updating the beamforming matrix and the maximum power constraint of the small cell base station that maximizes the SINR or meets a predetermined criterion and updates the uplink and the small size of the wireless backhaul link A small cell which satisfies the target transmission rate of the cell downlink as a minimum power The power allocation vector of the base station, and the maximum power limitation condition.

In addition, an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul according to another embodiment is characterized in that each small cell base station is capable of receiving location information of the small cell base stations And an interference controller for performing distributed interference control so as to optimize beam forming and power distribution using the beamforming and power distribution of the base station and the small cell base stations, can do.

Wherein the interference control unit includes: an initialization unit for initializing a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station, and a power allocation vector of the user terminal; The power allocation vector of a user terminal belonging to a small cell that satisfies the target transmission rate of the small-size cell uplink with the minimum power is updated, and the signal-to-interference plus noise ratio , SINR) or a beamforming matrix of a small cell base station that meets a predetermined criterion, and updates the beamforming matrix of the small cell base station satisfying the maximum transmission power of the uplink and the target transmission rate of the small- And a calculation unit for updating the power allocation vector.

A fixed beam forming and power allocation designing unit for designing a fixed beam forming matrix to obtain a beamforming matrix of a wide area cell base station and a fixed power allocation matrix to obtain a power allocation vector of a wide area cell base station.

Embodiments use inverse time division multiple access (Reverse-TDD) to control interference factors occurring in a multi-layer heterogeneous network system using an in-band wireless backhaul, It is possible to provide a method and an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using an in-band wireless backhaul that controls a residual interference signal through a power allocation technique.

From the technical point of view, it is possible to efficiently use the frequency resources through the interference control of the in-band wireless backhaul system and achieve the increase of the total network capacity through the space reuse of the small cell network.

In addition, from an economical point of view, it is possible to reduce the installation cost of a wired backhaul by using a wireless backhaul, and to reduce energy consumption through a power minimization interference control method.

FIG. 1 is a diagram illustrating a reverse-TDD-based 2-layer heterogeneous network system according to an embodiment.
2 is a diagram for explaining the operation of reverse-TDD in a multi-layer heterogeneous network using a wireless backhaul according to an exemplary embodiment.
3 illustrates an uplink and downlink interference control method of a multi-layer heterogeneous network using a centralized interference control method according to an exemplary embodiment.
FIG. 4 illustrates an uplink and downlink interference control method of a multi-layer heterogeneous network using a dispersion-based interference control method according to another embodiment.
5 is a diagram of a network topology according to one embodiment.
6 is a diagram illustrating the convergence of the algorithm according to an embodiment.
7 is a diagram for explaining a power consumption comparison with an optimum performance according to an embodiment.
FIG. 8 is a diagram illustrating a comparison of interference control performance of a centralized interference control and dispersion scheme according to an embodiment.
9 is a diagram illustrating a comparison of power consumption according to the number of small cell base station (SBS) antennas according to an embodiment.

Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the embodiments described may be modified in various other forms, and the scope of the present invention is not limited by the embodiments described below. In addition, various embodiments are provided to more fully describe the present invention to those skilled in the art. The shape and size of elements in the drawings may be exaggerated for clarity.

Embodiments of the present invention will be described herein with reference to the relationship between data transmission and reception between a base station and a terminal. Here, the BS has a meaning as a terminal node of a network that directly communicates with the MS. The particular operation described below to be performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, it is apparent that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station (BS)' may be replaced by a term such as a fixed station, a Node B, an eNode B (eNB), an access point (AP) Also, the term base station below can be used as a concept including a cell or a sector. Meanwhile, the repeater can be replaced by terms such as Relay Node (RN) and Relay Station (RS). The term 'terminal' may be replaced with terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station), SS (Subscriber Station)

The specific terminology used in the following description is provided to aid understanding of the present invention, and the use of such specific terminology may be changed into other forms without departing from the technical idea of the present invention.

In some instances, well-known structures and devices may be omitted or may be shown in block diagram form, centering on the core functionality of each structure and device, to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.

In a next generation mobile communication system, a technique of increasing the capacity per area by using a plurality of small cell base stations together with a wireless backhaul network which is easy to install is attracting attention. In particular, for an in-band wireless backhaul system that uses the same frequency as the access channel, interference problems occur between the wireless backhaul and the access channel. Therefore, an optimal interference control technique is required to satisfy users' data traffic demands within a given wide cell base station, small cell base station, and user transmission power. The following embodiments propose an interference control method considering uplink and downlink in an in-band wireless backhaul environment.

The proposed system model uses a wider frequency resource by simultaneously operating a wide-area cell link (wireless backhaul channel) and a small cell link (connection channel) in the same band (in-band). However, by using Reverse-Time Division Duplex (Reverse-TDD), interference between the wide-area cell base station and the users can be avoided by reversing the direction of the uplink and downlink . Other interference factors can be controlled through beamforming techniques using multiple antennas and power allocation techniques.

The capacity of a link connected from a wide area cell base station to a user via a small cell base station is limited by a small value of the capacity of each small cell and the capacity of the corresponding wireless backhaul. In addition to this condition, the beam forming and power distribution of the wide cell base station and all the small cell base stations can be simultaneously optimized to minimize the transmission power of the base stations. Also, it is possible to provide a decentralized interference control method in which each small cell base station can optimize beam forming and power distribution without using a wide area cell base station only by using position information of small cell base stations.

First, the symbols used below are described.

은 광역셀 기지국(MBS)의 안테나 수이고,

은 소형셀 기지국(SBS)의 안테나 수이며,

은 소형셀 수이고,

은 소형셀 당 사용자 단말 수이며,

은 광역셀 기지국(MBS), 소형셀 기지국(SBS) 및 사용자 단말(UE)의 잡음전력이다. 그리고

은 광역셀 기지국(MBS)과 l 번째 소형셀 기지국(SBS) 사이의 복소 채널 행렬,

이며,

은 l 번째 소형셀 기지국(SBS)과 j 번째 소형셀의 k 번째 사용자 단말(UE) 사이의 복소 채널 벡터,

이고,

은 광역셀 기지국(MBS)의 빔 형성 행렬,

이며,

은 l 번째 소형셀 기지국(SBS)의 빔 형성 행렬,

이고,

은 광역셀 기지국(MBS)의 전력 할당 벡터,

이며,

은 l 번째 소형셀 기지국(SBS)의 전력 할당 벡터,

이고,

은 l 번째 소형셀에 속한 사용자 단말(UE)들의 전력 할당 벡터,

이다. 또한,

은 기댓값 연산자(Expectation operator)이며,

은

단위 행렬(Identity matrix)이고,

은 전치(transpose)/켤레 전치(conjugate transpose)이며, 함수

은 matrices pair

의 단위 표준을 갖는 지배적인 일반화된 고유 벡터를 나타낸다.

Is the number of antennas of the wide area cell base station MBS,

Is the number of antennas of the small cell base station (SBS)

Is a small cell number,

Is the number of user terminals per small cell,

Is the noise power of the wide area cell base station (MBS), the small cell base station (SBS) and the user terminal (UE). And

Is a complex channel matrix between the wide area cell base station (MBS) and the l-th small-cell base station (SBS),

Lt;

Is a complex channel vector between the lth small cell base station (SBS) and the kth user terminal (UE) of the jth small cell,

ego,

A beamforming matrix of a wide area cell base station MBS,

Lt;

Is a beamforming matrix of the lth small cell base station (SBS)

ego,

A power allocation vector of the wide area cell base station MBS,

Lt;

Is the power allocation vector of the 1 st small cell base station (SBS)

ego,

The power allocation of the user terminal (UE) belonging to the l-th small cell vector,

to be. Also,

Is an expectation operator,

silver

Is an identity matrix,

Is a transpose / conjugate transpose,

Matrices pair

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

FIG. 1 is a diagram illustrating a reverse-TDD-based 2-layer heterogeneous network system according to an embodiment.

Referring to FIG. 1, in a 2-layer heterogeneous network, an uplink (UL) and a downlink (UL) of a first tier and a second tier are established using an inverse time division multiple access (DL) mode are staggered from each other, so that a user equipment (UE) can avoid strong interference from a macro cell base station (MBS). Here, the first layer is a wireless backhaul link between one wide area cell base station (MBS) and a plurality of small cell base stations (SBSs), the second layer is a small backhaul link between small cell base stations (SBSs) And is a link between terminals UEs.

In a 2-layer heterogeneous network system based on reverse-TDD, uplink and downlink transmission can be performed alternately through two time slots based on reverse-TDD.

2 is a diagram for explaining the operation of reverse-TDD in a multi-layer heterogeneous network using a wireless backhaul according to an exemplary embodiment.

FIG. 2A illustrates time slot 1 of a reverse-TDD in a multi-layer heterogeneous network using a wireless backhaul according to an exemplary embodiment. FIG. 2B illustrates an example of reverse-TDD in a multi-layer heterogeneous network using a wireless backhaul according to an exemplary embodiment. Represents time slot 2.

In the time slot 1, downlink transmission of the first layer and uplink transmission of the second layer are performed. In the time slot 2, transmission in the opposite direction to the time slot 1 is performed. That is, in the time slot 2, uplink transmission of the first layer and downlink transmission of the second layer can be performed.

Referring to FIG. 2A, the first layer channel model can be confirmed.

개 안테나를 가진 광역셀 기지국(MBS, 210)과

개 안테나를 가진 l 번째 소형셀 기지국(SBS, 220) 사이의 하향 링크 채널 행렬

는 크기가

이며, 대규모(large-scale) 채널 이득

와 소규모(small-scale) 채널 이득

을 모두 포함할 수 있다. 여기서,

은 광역셀 기지국(MBS, 210)의 안테나 수이고,

은 소형셀 기지국(SBS, 220)의 안테나 수이다.

A wide area cell base station (MBS) 210 having an antenna

The downlink channel matrix between the l th small cell base station (SBS) 220 having two antennas

Is the size

, And a large-scale channel gain

And small-scale channel gain

May be included. here,

Is the number of antennas of the wide area cell base station (MBS) 210,

Is the number of antennas of the small cell base station (SBS) 220.

On the other hand, since the wide area cell base station (MBS) 210 is mainly installed in a high building or a mountain peak, a small-scale channel of the first layer channel can be modeled as a one-ring channel, The channel matrix can be expressed by the following equation.

[Formula 1]

은 광역셀 기지국(MBS, 210)과 l 번째 소형셀 기지국(SBS, 220) 사이의 복소 채널 행렬,

이다. here,

Is a complex channel matrix between the wide area cell base station (MBS, 210) and l-th small cell base stations (SBS, 220),

to be.

로 나타낼 수 있으며, 다음 식과 같이 주어질 수 있다.And the channel covariance matrix for the 1 st small cell base station (SBS, 220)

And can be given by the following equation.

[Formula 2]

는 배열 조향 벡터(array steering vector)이며, 광역셀 기지국(MBS, 210)이 UPA(Uniform Planar Array)를 사용하는 경우 다음 식과 같이 나타낼 수 있다.here,

Is an array steering vector, and when a wide area cell base station (MBS) 210 uses a UPA (Uniform Planar Array), it can be expressed as the following equation.

[Formula 3]

은 전치(transpose)를 나타내고,

와

는 UPA의 가로 및 세로 방향의 안테나 수이다.here,

Represents a transpose,

Wow

Is the number of antennas in the horizontal and vertical directions of the UPA.

로 가정한다.On the other hand, the uplink channel of the second layer is divided into a plurality of uplink channels by a channel reciprocity of a time division duplex (TDD)

.

Referring to FIG. 2B, the second layer channel model can be confirmed.

개 안테나를 가진 l 번째 소형셀 기지국(SBS, 220)과 단일 안테나를 가진 각 사용자 단말(UE, 240) 사이의 채널 벡터는 길이가

이며 대규모(large-scale) 채널 이득

와 소규모(small-scale) 채널 이득

로 구성된다. 여기서,

는 i.i.d. 레일리(Rayleigh) 채널로 모델링 할 수 있다. 이 경우 l 번째 소형셀(230)의 k 번째 사용자 단말(UE, 240)과 l 번째 소형셀 기지국(SBS, 220) 사이의 상향 링크 채널은 다음 식과 같이 나타낼 수 있다.

The channel vector between the l th small cell base station (SBS, 220) having one antenna and each user terminal (UE, 240) having a single antenna has a length

And a large-scale channel gain

And small-scale channel gain

. here,

Can be modeled as an iid Rayleigh channel. Uplink channel between the k th user terminal in this case l in the second small cell (230) (UE, 240) and l-th small cell base stations (SBS, 220) can be expressed by the following equation.

[Formula 4]

은 l 번째 소형셀 기지국(SBS, 220)과 j 번째 소형셀(230)의 k 번째 사용자 단말(UE, 240) 사이의 복소 채널 벡터,

이다. here,

Is a complex channel vector between the lth small cell base station (SBS, 220) and the kth user terminal (UE, 240) of the jth small cell 230,

to be.

로 가정한다.
The downlink channel is determined by the channel reversibility of the TDD system

.

The signal-to-interference plus noise ratio (SINR) of the received signal for each link can be expressed as follows.

은 소형셀(230) 수이고,

은 소형셀(230) 당 사용자 단말 수이다.Referring again to Figure 2a, a wide area cell for the downlink in a time slot 1 in the l-th small cell base stations (SBS, 220) (Macro cell Downlink) can be expressed by the following equation. Meanwhile,

Is the number of small cells 230,

Is the number of user terminals per small cell 230.

[Formula 5]

은 광역셀 기지국(MBS, 210)의 전력 할당 벡터,

이고,

은 소형셀 기지국(SBS, 220)의 빔 형성 행렬,

이다. here,

The power allocation vector of the wide area cell base station (MBS) 210,

ego,

A beamforming matrix of the small cell base station (SBS) 220,

to be.

와

는 각각 다음 식과 같이 나타낼 수 있다.procession

Wow

Can be expressed by the following equations respectively.

[Formula 6]

은 광역셀 기지국(MBS, 210)의 빔 형성 행렬,

이며,

은 l 번째 소형셀 기지국(SBS, 220)의 전력 할당 벡터,

이고,

은 l 번째 소형셀(230)에 속한 사용자 단말(UE, 240)들의 전력 할당 벡터,

이며,

은

단위 행렬(Identity matrix)이다. here,

A beamforming matrix of the wide area cell base station (MBS) 210,

Lt;

Is the power allocation vector of the 1 st small cell base station (SBS, 220)

ego,

The power allocation vector of user terminals UE 240 belonging to the 1 st small cell 230,

Lt;

silver

It is an identity matrix.

The uplink (small cell uplink) of the kth user terminal (UE) 240 of the l th small cell 230 in the time slot 1 can be expressed by the following equation.

[Equation 7]

와

는 각각 다음 식과 같이 나타낼 수 있다.Here,

Wow

Can be expressed by the following equations respectively.

[Equation 8]

Referring again to FIG. 2B, a macro cell uplink for the 1 st small cell base station (SBS) 220 in the time slot 2 can be expressed by the following equation.

[Equation 9]

와

는 각각 다음 식과 같이 나타낼 수 있다.Here,

Wow

Can be expressed by the following equations respectively.

[Equation 10]

K th user terminal of the l-th small cell 230 in time slots 2 small cell DL (Downlink Small cell) of (UE, 240) can be expressed by the following equation.

[Equation 11]

와

는 각각 다음 식과 같이 나타낼 수 있다.here,

Wow

Can be expressed by the following equations respectively.

[Equation 12]

Hereinafter, an uplink and downlink interference control method and apparatus of a multi-layer heterogeneous network using a two-layer heterogeneous network, for example, an in-band wireless backhaul will be described.

The conditions to be satisfied in beam forming (precoding) and power allocation design of 2-layer heterogeneous network are as follows. 2) a condition that the transmission rate of each link of the first layer should be higher than the sum of the small cell rate of the second layer corresponding thereto, and 3) Is the maximum transmission power condition (maximum power condition) for the base station (MBS), the small cell base station (SBS) and the user terminal (UE). Here, the beam is an antenna pattern formed according to a weight vector multiplied by the antenna array at the transmitting end.

Considering these three conditions, the optimization problem for power minimization can be expressed as follows.

The objective is to minimize the sum of all transmission powers of a wide area cell base station (MBS), a small cell base station (SBS), and a user terminal (UE).

[Formula 13]

In this case, constraints are defined as a backhaul capacity condition, a minimum target rate condition of each user equipment (UE), and a maximum power limitation condition.

[Equation 14]

는 각 사용자 단말(UE)에게 보장해야 하는 소형셀 하향 링크 목표 전송률이고,

는 각 사용자 단말(UE)에게 보장해야 하는 소형셀 상향 링크의 목표 전송률이다.
here,

Is a small cell downlink target transmission rate that should be guaranteed to each user terminal (UE)

Is a target transmission rate of a small cell uplink to be guaranteed to each user terminal (UE).

The following provides a revised problem to ensure feasibility.

과

에 비해서 최대 전력조건이 충분하지 않을 경우, 실행 불가능한(infeasible) 문제가 될 수 있으며, 이러한 경우 문제를 풀 수 없다. 그러나 실행 불가능한 경우라도 활성화된(active) 사용자 단말(UE)이 존재하는 한 주어진 전력조건하에서 최대의 전송률을 보장하도록 빔 형성 및 전력 할당을 할 수 있어야 한다.The above-described [Expression 13] problem is that the target transmission rate

and

If the maximum power condition is not sufficient, it may be an infeasible problem, and in such a case, the problem can not be solved. However, even if it is not feasible, beam forming and power allocation should be possible to ensure the maximum data rate under a given power condition as long as there is an active user terminal (UE).

Therefore, the problem is to design beam forming and power allocation satisfying the target transmission rate at a given power condition by modifying the problem to always guarantee the feasibility. Thereafter, if it turns out to be a feasible problem, an additional power minimization process is performed to achieve the original purpose. The modified problem can be described as follows.

The objective is to maximize the minimum ratio of uplink and downlink SINRs of all layers to the corresponding target SINR.

[Formula 15]

In this case, the constraints are maximum power limiting conditions and can be expressed as the following equation.

[Formula 16]

이고, 또한 함수

는

중 가장 작은 값과 같다.here,

Also,

The

Which is the smallest of the two.

In order to solve [Expression 15] presented as a problem, a centralized interference control method and a decentralized interference control method can be provided.

Centralized interference management method (Centralized interference management)

3 illustrates an uplink and downlink interference control method of a multi-layer heterogeneous network using a centralized interference control method according to an exemplary embodiment.

Referring to FIG. 3, a method for controlling uplink and downlink interference of a multi-layer heterogeneous network using a centralized interference control method according to an exemplary embodiment of the present invention includes: (310) receiving information on a target rate condition and a power limitation condition, performing centralized interference control for beam forming and power allocation of the entire network using channel information in a wide area cell base station 320, and optimizing beamforming and power allocation to the corresponding small cell base station (330).

And transmitting (340) the power allocation value to the user terminals of the small cell in each of the small cell bases.

Hereinafter, an uplink and downlink interference control method of a multi-layer heterogeneous network using a centralized interference control method according to one embodiment will be described in more detail. Meanwhile, an apparatus for controlling uplink and downlink interference of a multi-layer heterogeneous network using a centralized interference control method according to an exemplary embodiment may include an information collecting unit, an interference controlling unit, and a transmitting unit. Here, the information collecting unit, the interference control unit, and the transmitting unit may be comprised of a device included in a wide area cell base station (MBS) or a device including a wide area cell base station (MBS).

를 알고 있고, l 번째 소형셀 기지국(SBS)은

와

를 알고 있다고 가정한다. The wide area cell base station (MBS)

, And the 1 st small cell base station (SBS) knows

Wow

.

정보를 전달받을 수 있다.In step 310, the information collecting unit may receive channel information on the network, a minimum target rate condition of each user terminal, and information on the power restriction condition from the small cell base stations. That is, the wide area cell base station MBS is transmitted from all small cell base stations (SBS)

Information can be received.

이다. In step 320, the interference controller may perform centralized interference control for beamforming and power allocation of the entire network using channel information in a wide area cell base station. In other words, centralized interference control for beam forming and power allocation design of the entire network can be performed using all the channel information in the wide area cell base station (MBS). At this time, the overall optimization variable

to be.

In particular, in order to enable simultaneous operation in the same band of a multi-layer heterogeneous network, the uplink and downlink directions of each tier are reversed by using reverse time division duplex (Reverse-TDD) It is possible to avoid inter-link interference.

In step 330, the transmitter may transmit the optimized beamforming and power allocation parameters to the respective small cell base stations. The transmitter can transmit the parameters of the beamforming matrix of the small cell base station, the power allocation vector of the small cell base station, and the power allocation vector of the user terminals belonging to the small cell to the small cell base station.

이다. That is, the optimized beamforming and power allocation parameters can be transmitted to the corresponding small cell base station (SBS). Here, the variable corresponding to the l- th small cell base station (SBS)

to be.

이다.
Accordingly, in step 340, each small cell BS can transmit a power allocation value to the user terminals of the small cell. That is, each small cell base station (SBS) can transmit the power allocation value to the K user terminals (UEs) of the corresponding cell. Here,

to be.

The following Table 1 is the algorithm 1 representing the centralized interference control method.

[Table 1]

(320) of performing centralized interference control for beamforming and power allocation of the entire network using the channel information in the wide area cell base station will be described in detail.

The interference control unit may include an initialization unit, a target rate setting unit, and a calculation unit.

The initialization unit may initialize the beamforming matrix of the wide cell base station and the beamforming matrix of the small cell base station. Then, the power allocation vector of the wide area cell base station, the power allocation vector of the small cell base station, the power allocation vector of the user terminal, and the maximum power limitation condition can be initialized.

The target transmission rate setting unit may set the target transmission rate of the wireless backhaul link so as not to be smaller than the transmission rate of the small cell.

The estimation unit may update the signal-to-interference plus noise ratio (SINR) of the received signal for each link of the wireless backhaul link or update the beamforming matrix of the wide area cell base station satisfying a predetermined criterion.

Then, the estimator can update the power allocation vector of the wide area cell base station satisfying the target transmission rate of the wireless backhaul link with the minimum power as much as possible.

Thereafter, the estimating unit may update the power allocation vector and the maximum power limitation condition of the user terminal belonging to the small cell that satisfies the target transmission rate of the small cell uplink with the minimum power as much as possible.

The estimator may update the beamforming matrix and the maximum power constraint of the small cell base station that maximizes the signal-to-interference-plus-noise ratio (SINR) or meets predetermined criteria.

Then, the estimator can update the power allocation vector and the maximum power limitation condition of the small cell base station that satisfies the target transmission rate of the uplink and the small cell downlink of the wireless backhaul link with the minimum power as much as possible.

This can be repeated until a predetermined convergence condition is satisfied.

Accordingly, it is possible to simultaneously optimize the beam forming and the power distribution of the wide cell base station and the small cell base stations so as to minimize the transmission power of the base stations.

Distributed interference management (Distributed interference management)

As the number of small cells increases and the number of antennas of the base station increases, the channel information exchange amount for performing centralized interference control and the computational complexity of the algorithm become very high, making it difficult to use in a realistic system.

The beamforming matrix F of the wide area cell base station MBS and the power allocation vector q are fixed by the design based on the location information of the small cell base stations SBS, regardless of the instantaneous channel information, SBS), and the computational complexity of the centralized interference control method can be distributed to each small cell base station (SBS) so that it can be used in a realistic system.

This is because the first-layer wireless backhaul channel is closely related to the location information due to the narrow angular spread characteristic, and when using a large number of antennas, the channel hardening effect causes a small-scale, It is possible to use the effect of disappearing fading.

FIG. 4 illustrates an uplink and downlink interference control method of a multi-layer heterogeneous network using a dispersion-based interference control method according to another embodiment.

Referring to FIG. 4, a method for controlling uplink and downlink interference of a multi-layer heterogeneous network using a dispersion-based interference control method according to another embodiment includes uplink and downlink interference control of an in- The interference control method may include a step 410 of performing distributed interference control to optimize beamforming and power distribution using location information of the small cell base stations without the help of a wide area cell base station have.

And transmitting (420) the power allocation value to the user terminals of the small cell in each small cell base station. The beam forming and power distribution of the wide cell base station and the small cell base stations are minimized to minimize the transmission power of the base stations. It can be optimized at the same time.

Hereinafter, an uplink / downlink interference control method of a multi-layer heterogeneous network using an interference control method of a distributed system according to another embodiment will be described in more detail. Meanwhile, an uplink and downlink interference control apparatus of a multi-layer heterogeneous network using a distributed interference control method according to another embodiment may include an interference control unit and a transmission unit. Here, the interference controller and the transmitter may be comprised of a small cell base station (SBS) or a small cell base station (SBS).

In step 410, the interference controller may perform the distributed interference control so that each small cell base station optimizes the beamforming and power distribution using the location information of the small cell base stations without the help of the wide cell base station.

In particular, in order to enable simultaneous operation in the same band of a multi-layer heterogeneous network, the uplink and downlink directions of each tier are reversed by using reverse time division duplex (Reverse-TDD) It is possible to avoid inter-link interference.

In step 420, the transmitting unit may transmit the power allocation value to the user terminals of the small cell in each small cell base station.

설계방법1) Fixed beamforming matrix

Design Method

은 광역셀 기지국(MBS)의 배열 응답 벡터(array response vector)와 소형셀 기지국(SBS) 위치 및 확산 각도(angular spread)를 알고 있는 경우 [식 2]를 이용하여 계산 가능하다.The channel covariance matrix of each wireless backhaul channel of the first tier

Can be calculated using Equation (2) if the array response vector of the wide area cell base station (MBS) and the location of the small cell base station (SBS) and the angular spread are known.

Meanwhile, small-scale fading disappears due to the massive multi-input multi-output (MIMO) theory when a large number of antennas are used, The intra-tier interference control and the beamforming gain of the first layer can be obtained by using the channel covariance matrix depending on the SBS position information.

를 구성하는 열 벡터들은 SINR을 최대화 하는 경우 다음 식과 같이 구할 수 있다.Fixed Beamforming Matrix

Can be obtained as shown in the following equation when the SINR is maximized.

[Formula 17]

은 matrices pair

의 단위 표준을 갖는 지배적인 일반화된 고유 벡터를 나타낸다. 그리고,

이다. Here,

Matrices pair

Lt; RTI ID = 0.0 > normalized < / RTI > And,

to be.

설계방법2) fixed power allocation vector

Design Method

은 다음 식과 같이 구할 수 있다.A fixed power allocation for satisfying a target transmission rate of the first layer link

Can be obtained by the following equation.

[Formula 18]

이며, j 번째 소형셀 기지국(SBS)에 대하여

가 가지는 통계적 빔 형성 이득

은 다음 식과 같이 계산할 수 있다.here,

, And for the j- th small cell base station (SBS)

The statistical beam forming gain

Can be calculated as follows.

[Formula 19]

는 다음 식과 같이 정의할 수 있다. Also,

Can be defined as follows.

[Formula 20]

을 도입하며, 광역셀 기지국(MBS) 안테나 수가 증가할수록 채널 하드닝(channel hardening) 효과로 인해

값을 줄일 수 있다.On the other hand, if only the covariance information of the channel is designed, it may happen that the channel condition is not instantly available and the target transmission rate of the first layer can not be satisfied. In this case, the fading margin

And the channel hardening effect as the number of MBS antennas increases.

You can reduce the value.

The following Table 2 is Algorithm 2 showing the interference control method of the distributed scheme.

[Table 2]

(410) performing dispersion-based interference control to optimize beamforming and power distribution using the location information of the small cell base stations will be described in more detail.

The interference control unit may include an initialization unit and a calculation unit.

The initialization unit may initialize the beamforming matrix of the small cell base station, the power allocation vector of the small cell base station, and the power allocation vector of the user terminal.

The estimating unit may update the power allocation vector of the user terminal belonging to the small cell that satisfies the target transmission rate of the small cell uplink with the minimum power as much as possible.

Thereafter, the estimator may update the signal-to-interference plus noise ratio (SINR) of the received signal for each link of the wireless backhaul link or update the beamforming matrix of the small cell base station satisfying a predetermined criterion .

Then, the estimator can update the power allocation vector of the small cell base station that satisfies the target transmission rate of the uplink and the small cell downlink of the wireless backhaul link with the minimum power as much as possible. This can be repeated until a predetermined convergence condition is satisfied.

Meanwhile, according to an embodiment, the interference controller calculates a beamforming matrix of a wide area cell base station by designing a fixed beamforming matrix, and design a fixed power allocation matrix to obtain a fixed beamforming and power allocation design unit .

The following shows the simulation results.

Here, the wide area cell base station (MBS) uses UPA, and the path loss can be assumed to be as follows.

[Formula 21]

는 광역셀 기지국(MBS)과 l 번째 소형셀 기지국(SBS) 사이의 거리를 미터 단위로 나타낸 것이며,

는 l 번째 소형셀 기지국(SBS)과 j 번째 소형셀의 k 번째 사용자 단말(UE) 사이의 거리를 나타낸 것이다.here,

Will showing a distance between the wide area cell base station (MBS) and the l-th small-cell base station (SBS) in meters,

Is the distance between the lth small cell base station (SBS) and the kth user terminal (UE) of the jth small cell.

dB로 설정하였다.The set of two parameters shown in Table 3 below is used, and the target transmission rate of the uplink is always set to 0.5 times the downlink target transmission rate. In the case of distributed interference control, the fading margin is

dB.

Table 3 shows the simulation parameters.

[Table 3]

5 is a diagram of a network topology according to one embodiment.

In this simulation, two network topographical diagrams are considered. FIG. 5A shows a network topology of the parameter set A, and FIG. 5B shows a network topology of the parameter set B. FIG.

There are three small cells in the parameter set A, eight small cells in the parameter set B, and two user terminals UE (shown in the figure) in each small cell.

6 is a diagram illustrating the convergence of the algorithm according to an embodiment.

FIG. 6A shows a centralized interference control, and FIG. 6B shows a dispersion-based interference control, whereby the convergence performance of two interference control algorithms can be confirmed. Here, the convergence condition is the sum of the total power consumption.

값만 나타내었다.As shown in FIG. 6B, in the case of the interference control of the dispersion scheme,

Value only.

Both algorithms, centralized interference control and distributed interference control, show that the overall power consumption decreases monotonically and converges. In the case of dispersion-based interference control, the convergence speed is also very fast since the degree of freedom of the optimization variable is significantly reduced as compared with the centralized interference control.

7 is a diagram for explaining a power consumption comparison with an optimum performance according to an embodiment.

Referring to FIG. 7, the optimum performance and power consumption are compared in the case of using the parameter set A, and the above-described optimization problem (13) is solved for brute force approaches and the algorithm 1 Of the power consumption.

The brute force is the performance when solving optimization problems directly with MATLAB's fmincon function and is considered to be the local optimal performance of the given problem. In this method, the average value is calculated only when the convergence is achieved using the parameter set A having a relatively low parameter value because the convergence is not guaranteed and the calculation complexity is high.

In addition, optimization results for the out-of-band wireless backhaul system are shown, in which case the bandwidth division ratio between the wireless backhaul and the access channel is optimized and beamforming and power allocation are optimized.

An in-band wireless backhaul system using a centralized interference control method (algorithm 1) can consume less power than an out-of-band wireless backhaul system.

A comparison of the performance of the in-band wireless backhaul system shows that the centralized interference control method (Algorithm 1) at the target downlink target rate = 80 Mbps has a difference of about 0.63 dB compared to the performance using the brute force It can be confirmed that it is close.

FIG. 8 is a diagram illustrating a comparison of interference control performance of a centralized interference control and dispersion scheme according to an embodiment.

Referring to FIG. 8, the performance of the centralized interference control (Algorithm 1) and the distributed interference control (Algorithm 2) can be compared using the parameter set B.

8A, the distributed interference control (algorithm 2) requires no information exchange between the wide area cell base station MBS and the small cell area base station SBS, and the calculation complexity is also controlled by the centralized interference control (algorithm 1) Instead of lower than the scheme, it consumes 2.2 dB more power.

를 150개에서 200개로 증가시키는 경우 전체 전력 소모는 약 0.9 dB 줄어들게 되어 실행 가능한 전송률 영역(feasible rate region)이 늘어나게 된다. Also,

Is increased from 150 to 200, the total power consumption is reduced by about 0.9 dB, thereby increasing the feasible rate region.

At the same time, FIG. 8B shows the sum of the difference between the achievable transmission rate and the target transmission rate for each link. It can be seen that both the centralized interference control (Algorithm 1) and the distributed interference control (Algorithm 2) satisfy the conditions in the low target rate region and the decentralized interference control (Algorithm 2) ) Achieves about 90% of the maximum target transmission rate range guaranteed by the present invention.

9 is a diagram illustrating a comparison of power consumption according to the number of small cell base station (SBS) antennas according to an embodiment.

Referring to FIG. 9, it is shown that the parameter set B is used, and the total power consumption is reduced by about twice (3 dB) each time the number of small cell base station (SBS) antennas is doubled. This is because the change in the number of small cell base station (SBS) antennas affects both the uplink and downlink performance of the first layer and the second layer. Therefore, it is expected that the proposed centralized interference control algorithm (Algorithm 1) and the distributed interference control algorithm (Algorithm 2) will increase the target target transmission rate range as the number of small cell base station (SBS) antennas increases.

In a next generation mobile communication network, the number of cells is gradually decreasing and the number of cells is increasing. Many small cell basestations need to be connected to the network through backhaul. At this time, technology related to wireless backhaul system, which has more freedom of installation and operation than wired backhaul system, is being actively developed and it is expected that related market do.

In order to perform optimal beamforming and power allocation for all links in a wide area cell base station, it is necessary to exchange channel information with small cell base stations. However, since large overhead is required to exchange a large amount of information from time to time, the present embodiment further provides a decentralized interference control method in consideration of practicality. This reduces system overhead and computational complexity, and each small cell base station can perform its own interference control without the help of a wide area cell base station. Therefore, autonomy of the network operation of the telecommunication service provider is enhanced.

In the near future, fixed and mobile small cell base stations equipped with multiple antennas such as buses, trains or unmanned mobile stations are expected to emerge in the form of repeaters. Through the interference control technology of the present patent, To operate wireless backhaul.

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, controller, arithmetic logic unit (ALU), digital signal processor, microcomputer, field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing apparatus may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device As shown in FIG. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like.

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. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (17)

A method for controlling uplink and downlink interference in a multi-layer heterogeneous network using an in-band wireless backhaul,
The wide area cell base station receives channel information on a network, a minimum target rate condition and a power limitation condition of each user terminal from the small cell base stations.
Performing centralized interference control for beam forming and power allocation of the entire network using the channel information in the wide area cell base station; And
And transmitting the optimized beamforming and power allocation parameters to the corresponding small cell base station
Wherein the uplink and downlink interference control method of the multi-layer heterogeneous network. The method according to claim 1,
Transmitting power allocation values to the user terminals of the small cell in each of the small cell basestations
Wherein the uplink and downlink interference control method of the multi-layer heterogeneous network further comprises: The method according to claim 1,
Performing centralized interference control for beam forming and power allocation of the entire network using the channel information in the wide area cell base station,
Setting a target transmission rate of the wireless backhaul link so as not to be smaller than a transmission rate of the small cell;
The method comprising: maximizing a signal-to-interference plus noise ratio (SINR) of a received signal for each link of the wireless backhaul link or updating a beamforming matrix of a wide area cell base station satisfying a predetermined criterion;
Updating a power allocation vector of a wide area cell base station that satisfies a target transmission rate of a downlink of the wireless backhaul link to a minimum power;
Updating a power allocation vector and a maximum power limitation condition of a user terminal belonging to a small cell that satisfies a target transmission rate of a small cell uplink with a minimum power as much as possible;
Updating the beamforming matrix and the maximum power constraint of the small cell base station that maximizes the SINR or satisfies a predetermined criterion; And
Updating the power allocation vector of the small cell base station and the maximum power limitation condition that satisfy the maximum transmission power of the uplink of the radio backhaul link and the target transmission rate of the small cell downlink to the minimum power,
/ RTI >
And repeatedly repeats the step until the predetermined convergence condition is satisfied. The method of claim 3,
Performing centralized interference control for beam forming and power allocation of the entire network using the channel information in the wide area cell base station,
Initializing a beamforming matrix of the wide area cell base station and a beamforming matrix of the small cell base station; And
Initializing a power allocation vector of the wide area cell base station, a power allocation vector of the small cell base station, a power allocation vector of the user terminal,
Further comprising:
Optimizing the beamforming and power distribution of the wide area cell base station and the small cell base stations simultaneously to minimize the transmission power of the base stations
And the uplink and downlink interference control method of the multi-layer heterogeneous network. The method according to claim 1,
Performing centralized interference control for beam forming and power allocation of the entire network using the channel information in the wide area cell base station,
By reversing the direction of the uplink and the downlink in each tier by using reverse time division duplex (Reverse-TDD) so that simultaneous operation in the same band of the multi-layer heterogeneous network is possible, Avoidance of interferences
And the uplink and downlink interference control method of the multi-layer heterogeneous network. The method according to claim 1,
Wherein the step of transmitting the optimized beamforming and power allocation parameters to the corresponding small cell base station comprises:
Transmitting a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station, and a power allocation vector variable of user terminals belonging to the small cell to the small cell base station
And the uplink and downlink interference control method of the multi-layer heterogeneous network. A method for controlling uplink and downlink interference in a multi-layer heterogeneous network using an in-band wireless backhaul,
Each of the small cell base stations performs a dispersion-type interference control so as to optimize beam forming and power distribution using the position information of the small cell base stations without the help of a wide-area cell base station
Wherein the uplink and downlink interference control method of the multi-layer heterogeneous network. 8. The method of claim 7,
Transmitting a power allocation value from each of the small cell basestations to user terminals of the small cell;
Further comprising:
Optimizing the beamforming and power distribution of the wide area cell base station and the small cell base stations simultaneously to minimize the transmission power of the base stations
And the uplink and downlink interference control method of the multi-layer heterogeneous network. 8. The method of claim 7,
The step of performing dispersion-based interference control to optimize beamforming and power distribution using the location information of the small cell base stations,
Updating a power allocation vector of a user terminal belonging to a small cell that satisfies a target transmission rate of a small-size cell uplink with a minimum power as much as possible;
Updating a beamforming matrix of a small cell base station satisfying a predetermined criterion or maximizing a Signal-To-Interference plus Noise Ratio (SINR) of a received signal for each link of a wireless backhaul link; And
Updating the power allocation vector of the small cell base station satisfying the maximum transmission power of the uplink of the wireless backhaul link and the target transmission rate of the small cell downlink to the minimum power;
/ RTI >
And repeatedly repeats the step until the predetermined convergence condition is satisfied. 10. The method of claim 9,
Initializing a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station, and a power allocation vector of the user terminal
Wherein the uplink and downlink interference control method of the multi-layer heterogeneous network. 10. The method of claim 9,
A fixed beamforming matrix is designed to obtain a beamforming matrix of a wideband cell base station; And
A step of calculating a power allocation vector of a wide area cell base station by designing a fixed power allocation matrix
Wherein the uplink and downlink interference control method of the multi-layer heterogeneous network. 8. The method of claim 7,
The step of performing dispersion-based interference control to optimize beamforming and power distribution using the location information of the small cell base stations,
By reversing the direction of the uplink and the downlink in each tier by using reverse time division duplex (Reverse-TDD) so that simultaneous operation in the same band of the multi-layer heterogeneous network is possible, Avoidance of interferences
And the uplink and downlink interference control method of the multi-layer heterogeneous network. An uplink and downlink interference control apparatus for a multi-layer heterogeneous network using an in-band wireless backhaul,
The wide area cell base station includes: an information collecting unit for receiving channel information on a network, a minimum target rate condition of each user terminal and information on a power limiting condition from small cell base stations;
An interference controller for performing centralized interference control for beamforming and power allocation of the entire network using the channel information in the wide area cell base station; And
And transmits the optimized beamforming and power allocation parameters to the corresponding small cell base station,
Lt; / RTI >
Optimizing the beamforming and power distribution of the wide area cell base station and the small cell base stations simultaneously to minimize the transmission power of the base stations
And the uplink and downlink interference control apparatus of the multi-layer heterogeneous network. 14. The method of claim 13,
Wherein the interference control unit comprises:
The beamforming matrix of the wide area cell base station and the beamforming matrix of the small cell base station are initialized and the power allocation vector of the wide area cell base station, the power allocation vector of the small cell base station, the power allocation vector of the user terminal, An initialization unit for initializing;
A target transmission rate setting unit setting a target transmission rate of the wireless backhaul link so as not to be smaller than a transmission rate of the small cell;
(SINR) of a received signal for each link of the wireless backhaul link or a beamforming matrix of a wide area cell base station satisfying a predetermined criterion is updated, and the wireless backhaul link The power allocation vector of the user terminal belonging to the small cell which satisfies the target transmission rate of the small cell uplink at the minimum power as much as possible and the maximum power allocation vector Updating the power constraint condition and updating the beamforming matrix and the maximum power constraint of the small cell base station that maximizes the SINR or meets a predetermined criterion and updates the uplink and the small size of the wireless backhaul link A small cell which satisfies the target transmission rate of the cell downlink as a minimum power The power allocation vector of the base station and the maximum power limitation condition,
And the uplink and downlink interference control apparatus of the multi-layer heterogeneous network. An uplink and downlink interference control apparatus for a multi-layer heterogeneous network using an in-band wireless backhaul,
Each of the small cell base stations performs an interference control of a distributed scheme so as to optimize beam forming and power distribution using the position information of the small cell base stations without the help of a wide cell base station,
Lt; / RTI >
Optimizing the beamforming and power distribution of the wide area cell base station and the small cell base stations simultaneously to minimize the transmission power of the base stations
And the uplink and downlink interference control apparatus of the multi-layer heterogeneous network. 16. The method of claim 15,
Wherein the interference control unit comprises:
An initialization unit for initializing a beamforming matrix of the small cell base station, a power allocation vector of the small cell base station and a power allocation vector of the user terminal;
The power allocation vector of a user terminal belonging to a small cell that satisfies the target transmission rate of the small-size cell uplink with the minimum power is updated, and the signal-to-interference plus noise ratio , SINR) or a beamforming matrix of a small cell base station that meets a predetermined criterion, and updates the beamforming matrix of the small cell base station satisfying the maximum transmission power of the uplink and the target transmission rate of the small- The power control unit
And the uplink and downlink interference control apparatus of the multi-layer heterogeneous network. 16. The method of claim 15,
Wherein the interference control unit comprises:
A fixed beamforming and power allocation design for finding a beamforming matrix of a wide area cell base station by designing a fixed beamforming matrix and obtaining a power allocation vector of a wide area cell base station by designing a fixed power allocation matrix
Further comprising: an uplink and downlink interference controller for a multi-layer heterogeneous network.

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