KR101680487B1 - Multicell beamforming method and system for ofdma small cell networks - Google Patents

Abstract

A multi-cell beamforming method in a small cell network based on OFDMA (Orthogonal Frequency Division Multiple Access) is a method in which a signal to interference plus noise (SINR) of each of a plurality of base stations is calculated based on a signal to noise ratio (SNR) Estimating a Ratio; And applying a Joint Client Association and Beam Selection (CABS) algorithm based on the SINR of each of the plurality of base stations to maximize utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients Determining a beam of each of the plurality of base stations and a connection of each of the plurality of clients.

Description

[0001] MULTICELL BEAM FORMING METHOD AND SYSTEM FOR OFDMA SMALL CELL NETWORKS [0002]

The following embodiments relate to a multi-cell beamforming system and a method thereof in a small cell network based on OFDMA (Orthogonal Frequency Division Multiple Access). More specifically, And determining a connection of each of the plurality of clients.

The proliferation of smartphones and tablet devices has led mobile operators to consider new technologies that provide increased network capacity. Thus, a technology in which small cells (cells in micro or picos units) are arranged at high density and used in 3G networks and 4G networks has been proposed.

However, such a technique has a problem that interference between small cells greatly affects network performance because small cells are arranged at a high density. In particular, in an OFDMA-based small cell network in which a plurality of clients receive the same frame, a method of handling interference between small cells is different from a method of processing in WiFi. Therefore, Is required.

Therefore, existing OFDMA-based small cell networks use a technique of handling interference between small cells in time or frequency domain by allocating orthogonal spectrum resources to interfering small cells.

However, the interference processing technique used in the existing OFDMA-based small cell network has disadvantages of wasting orthogonal spectrum resources.

In order to prevent waste of orthogonal spectrum resources, the following embodiments propose a technique of processing interference between small cells in a spatial domain using a beamforming antenna.

A multi-cell beamforming method and system according to an embodiment prevents a wasted orthogonal spectrum resource in an OFDMA-based small cell network and provides a technique for handling interference between small cells in a spatial domain.

In particular, a method and system for multi-cell beamforming according to an embodiment processes interferences between small cells in a spatial domain, and provides a technique for integrally determining a beam of each of a plurality of base stations and a connection of each of a plurality of clients do.

In addition, a method and system for multi-cell beamforming according to an exemplary embodiment of the present invention provides a technique for performing a beam determining process for each of a plurality of base stations separately from a scheduling process for a frame transmitted and received by a plurality of base stations.

In a small cell network based on OFDMA (Orthogonal Frequency Division Multiple Access) according to an exemplary embodiment, a multi-cell beamforming method includes calculating SINR (SINR) of each of a plurality of base stations based on a signal to noise ratio (SNR) Signal to interference plus noise ratio); And applying a Joint Client Association and Beam Selection (CABS) algorithm based on the SINR of each of the plurality of base stations to maximize utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients Determining a beam of each of the plurality of base stations and a connection of each of the plurality of clients.

Determining a beam of each of the plurality of base stations and a connection of each of the plurality of clients includes determining a connection of each of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations. Setting an initial beam of each of the plurality of base stations and an initial connection of each of the plurality of clients so that utilities of the plurality of clients are maximized; Updating an initial beam of each of the plurality of base stations; Determining a connection of each of the plurality of clients to maximize a utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients based on an initial beam of each of the updated plurality of base stations step; And determining a beam of each of the plurality of base stations based on a connection of each of the plurality of clients.

Wherein establishing an initial beam of each of the plurality of base stations and an initial connection of each of the plurality of clients comprises establishing an initial connection of each of the plurality of base stations and the plurality of clients associated with throughput of each of the plurality of clients Lt; RTI ID = 0.0 > a < / RTI > positive incremental value.

Wherein determining the connection of each of the plurality of clients comprises repeatedly calculating at least one or more times so that the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients is maximized can do.

The step of determining the connection of each of the plurality of clients may include calculating the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients to have a positive increment value .

Wherein determining the connection of each of the plurality of clients comprises comparing a number of times that the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients are repeatedly calculated to maximize the utilities, Or to determine a connection of each of the plurality of clients based on a result of comparing a predetermined threshold with a utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients Step < / RTI >

Wherein estimating the SINR of each of the plurality of base stations comprises: measuring an SNR of each of the plurality of base stations; And calculating an SINR of each of the plurality of base stations based on an SNR of each of the plurality of base stations.

Measuring the SNR of each of the plurality of base stations may comprise measuring an average SNR for the beams formed by each of the plurality of base stations.

The multi-cell beamforming method may further include performing scheduling on a frame transmitted and received by each of the plurality of base stations based on a beam of each of the plurality of base stations and a connection of each of the plurality of clients .

In a small cell network based on an Orthogonal Frequency Division Multiple Access (OFDMA) scheme according to an exemplary embodiment, a multi-cell beamforming system calculates a SINR of each of a plurality of base stations based on a signal to noise ratio (SNR) Signal to Interference plus Noise Ratio); And applying a Joint Client Association and Beam Selection (CABS) algorithm based on the SINR of each of the plurality of base stations to maximize utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients And a determination unit for determining a beam of each of the plurality of base stations and a connection of each of the plurality of clients.

Wherein the determining unit determines the initial beam and the initial beam of each of the plurality of base stations so that the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients is maximized based on the SINR of each of the plurality of base stations. Setting an initial connection of each of a plurality of clients, updating an initial beam of each of the plurality of base stations, and determining, based on the initial beam of each of the updated plurality of base stations, Determine a connection of each of the plurality of clients so that utilities of the plurality of base stations and the plurality of clients are maximized, and determine a beam of each of the plurality of base stations based on a connection of each of the plurality of clients.

The determination unit may calculate the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients among the plurality of clients to have a positive incremental value.

The determination unit may repeatedly calculate at least one or more times so that the utilities of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients are maximized.

Wherein the determination unit compares the number of times that the utilities of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients are repeatedly calculated so as to maximize the number of repetitions, Based on a result of comparing the utilities of the plurality of base stations and the plurality of clients with a preset threshold value associated with the plurality of base stations.

The multi-cell beamforming system may further include a scheduling unit for performing scheduling on a frame transmitted and received by each of the plurality of base stations based on a beam of each of the plurality of base stations and a connection of each of the plurality of clients .

The multi-cell beamforming method and system according to an embodiment can prevent a wasted orthogonal spectrum resource in an OFDMA-based small cell network and can provide a technique for handling interference between small cells in a spatial domain.

In particular, a method and system for multi-cell beamforming according to an embodiment processes interferences between small cells in a spatial domain, and provides a technique for integrally determining a beam of each of a plurality of base stations and a connection of each of a plurality of clients can do.

In addition, the method and system for multi-cell beamforming according to an embodiment can provide a technique of performing a process of determining beams of a plurality of base stations separately from a scheduling process for frames transmitted and received by a plurality of base stations have.

1 is a view for explaining a multi-cell beamforming method according to an embodiment.
FIG. 2 is a diagram illustrating throughputs by a multi-cell beamforming method according to an exemplary embodiment.
FIG. 3 is a diagram illustrating the accuracy of SINR (Signal to Interference plus Noise Ratio) estimated by the multi-cell beamforming method according to an exemplary embodiment.
FIG. 4 is a diagram illustrating a Joint Client Association and Beam Selection (CABS) algorithm according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating a multi-cell beamforming method according to an embodiment.
6 is a block diagram illustrating a multi-cell beamforming system in accordance with one embodiment.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to or limited by the embodiments. In addition, the same reference numerals shown in the drawings denote the same members.

1 is a view for explaining a multi-cell beamforming method according to an embodiment.

Referring to FIG. 1, the OFDMA-based small cell network transmits the same frame to each of the plurality of clients, so that the beam of each of the plurality of base stations affects the scheduling process for each of the plurality of clients . Also, the beam of each of the plurality of base stations affects the connection process of each of the plurality of clients.

,

및

각각의 연결이 결정된 이후, 복수의 기지국들

및

각각의 빔이 결정될 수 있다.Specifically, in the conventional case where SNR (Signal to Noise Ratio) is used as a matrix for connection of each of a plurality of clients as shown in (a)

,

And

After each connection is determined, a plurality of base stations

And

Each beam can be determined.

및

가 기지국

과 연결되고, 클라이언트

가 기지국

에 비해 상대적으로 SNR이 높은 기지국

에 연결된 후, 복수의 기지국들

및

각각은 연결되는 클라이언트와 통신하기 위한 최상의 빔을 결정하는 빔포밍 과정을 수행할 수 있다. 더 구체적인 예를 들면, 기지국

은 복수의 클라이언트들

및

각각과 통신하기 위해 빔

을 결정하고, 기지국

는 클라이언트

와 통신하기 위해 빔

를 결정할 수 있다.For example,

And

The base station

And the client

The base station

The base station having a relatively high SNR

And then, a plurality of base stations

And

Each can perform a beamforming process to determine the best beam to communicate with the connected client. More specifically, for example,

Lt; RTI ID = 0.0 >

And

In order to communicate with each other,

And determines,

The client

Lt; RTI ID = 0.0 > beam &

Can be determined.

이 클라이언트

와 통신하기 위해 빔

을 결정하면, 기지국

은 기지국

에 의해 클라이언트

와 통신하기 위하여 결정된 빔

에 의해 간섭을 받게 될 수 있다. 따라서, 복수의 클라이언트들

,

및

각각의 연결이 이미 고정된 후에 복수의 기지국들

및

각각의 빔이 결정되는 방식은 빔포밍에 따른 네트워크 성능을 제한하는 단점이 있다.However, in the conventional case where SNR is used as a matrix for connection of each of a plurality of clients,

This client

Lt; RTI ID = 0.0 > beam &

, The base station

The base station

By client

Lt; RTI ID = 0.0 > beam &

Lt; / RTI > Thus,

,

And

After each connection is already fixed, a plurality of base stations

And

The manner in which each beam is determined has the disadvantage of limiting network performance due to beamforming.

,

및

각각의 연결과 복수의 기지국들

및

각각의 빔이 통합적으로 결정될 수 있다.On the other hand, according to the multi-cell beam forming method according to the embodiment shown in (b) (hereinafter, the multi-cell beam forming method is performed by the multi-cell beam forming system)

,

And

Each connection and a plurality of base stations

And

Each beam can be determined integrally.

및

각각이 형성할 수 있는 모든 빔들의 조합 아래, 복수의 클라이언트들

,

및

각각의 연결이 결정된 후, 복수의 클라이언트들

,

및

각각의 연결에 따라 복수의 기지국들

및

각각의 최상의 빔이 결정될 수 있다. 더 구체적인 예를 들면, 클라이언트

는 기지국

에 비해 상대적으로 SNR이 낮은 기지국

에 연결될 수 있고, 기지국

는 복수의 클라이언트들

및

각각과 통신하기 위해 빔

를 결정하고, 기지국

은 클라이언트

과 통신하기 위해 빔

을 결정할 수 있다.For example, a plurality of base stations

And

Under all combinations of beams each can form, a plurality of clients

,

And

After each connection is determined, a plurality of clients

,

And

According to each connection, a plurality of base stations

And

Each best beam can be determined. More specifically, for example,

The base station

The base station having a relatively low SNR

And the base station

Lt; RTI ID = 0.0 >

And

In order to communicate with each other,

, And the base station

The client

Lt; RTI ID = 0.0 > beam &

Can be determined.

은 기지국

에 의해 복수의 클라이언트들

및

각각과 통신하기 위하여 결정된 빔

에 의해 간섭을 받지 않을 수 있고, 결과적으로 복수의 기지국들

및

각각은 모든 클라이언트들

,

및

에 대해 높은 SINR을 가질 수 있다. 이에 대한 상세한 설명은 도 2를 참조하여 기재한다.
Therefore,

The base station

Lt; RTI ID = 0.0 >

And

A beam < RTI ID = 0.0 >

And as a result, a plurality of base stations

And

Each of the clients

,

And

RTI ID = 0.0 > SINR < / RTI > A detailed description thereof will be described with reference to Fig.

FIG. 2 is a diagram illustrating throughputs by a multi-cell beamforming method according to an exemplary embodiment.

Referring to FIG. 2, it is assumed that there are two base stations and three clients connected to a plurality of base stations. Based on a plurality of topologies generated as the positions of the plurality of clients change, The network throughput in the conventional case 210 and the multi-cell beamforming method 220 according to an embodiment used as a matrix for the connection of each of the clients is shown.

In particular, the multi-cell beamforming method 220 according to one embodiment provides an average 25% gain in network throughput compared to the conventional case 210 where the SNR is used as a matrix for the connection of each of a plurality of clients And gain up to 40%.

As described above, the multi-cell beamforming method 220 according to an embodiment having superior network throughput compared to the conventional case 210 in which the SNR is used as a matrix for connection of each of a plurality of clients is described in detail below .

3 is a diagram illustrating the accuracy of the SINR estimated by the multi-cell beamforming method according to an exemplary embodiment.

3, a multi-cell beamforming system according to an exemplary embodiment estimates the SINR of each of a plurality of base stations in order to integrally determine a connection of each of a plurality of clients and a beam of each of a plurality of base stations.

At this time, the multi-cell beamforming system measures the SNR of each of the plurality of base stations (the average SNR is measured for the beams formed by each of the plurality of base stations), and then, based on the SNR of each of the plurality of base stations, The SINR of each of the plurality of base stations can be estimated, instead of directly measuring the SINR of each of the plurality of base stations.

은 수학식 1과 같이 표현될 수 있다.
here,

Can be expressed as Equation (1).

&Quot; (1) "

과 클라이언트 j 사이의 SINR은 SNR과 다른 기지국 사이의 잡음 비율에 의한 순 간섭과 관련이 있다(예컨대,

). 즉, 간섭이 제한된 스몰 셀들에서 INR+1

INR일 수 있다. 따라서, logarithmic(dB) domain에서, SINR(dB)=SNR(dB)-INR(dB)로 표현되어, 클라이언트에서 SINR은 연결되는 기지국 사이의 SNR과 간섭하는 모든 기지국 사이의 총 INR에 의해 추정될 수 있다.According to Equation 1,

And the client j are related to the net interference due to the SNR and the noise ratio between the other base stations (e.g.,

). That is, for small cells with limited interference, INR + 1

INR. Therefore, in the logarithmic (dB) domain, SINR (dB) = SNR (dB) -INR (dB), the SINR at the client is estimated by the total INR between all base stations interfering with the SNR between the connected base stations .

At this time, the SINR of the client may be influenced by various factors such as quantization, offset, estimation error, etc. in addition to the SNR between the connected base stations and the total INR between all base stations interfering with each other.

와 간섭이 존재하는 경우의

각각에 대해 클라이언트에서 관련된 기지국으로부터 신호 강도를 측정하고, 측정된 값으로부터

을 추정한 후, 클라이언트를 간섭하는 기지국과 개별적으로 연결시켜 신호 강도

를 기록한 결과, (a)와 같이

와

이 비교될 수 있다. 따라서, (a)를 살펴보면, 측정된 간섭 사이의 일정한 오프셋과 관련된 신호 강도가 클라이언트의 SNR과 무관하게 고정되어 있음을 알 수 있다. 이와 같은 오프셋이 반영되어 복수의 기지국들 각각의 SNR에 기초하여 추정되는 복수의 기지국들과 복수의 클라이언트들 각각 사이의 SINR은 수학식 2와 같이 표현될 수 있다.
For example, if there is no interference in a network environment with two small cells

And < RTI ID = 0.0 >

Measures the signal strength from the associated base station at the client for each,

, And then clients are individually connected to the interfering base station,

As a result, as shown in (a)

Wow

Can be compared. Thus, looking at (a), it can be seen that the signal strength associated with the constant offset between measured interferences is fixed irrespective of the client ' s SNR. The SINR between the plurality of base stations and each of the plurality of clients estimated based on the SNR of each of the plurality of base stations by reflecting such an offset can be expressed by Equation (2).

&Quot; (2) "

Also, looking at (b), the offset for the total interference may remain fixed (e.g., 4 dB) in dB. Accordingly, the multi-cell beamforming system according to an exemplary embodiment can estimate the SNR based on the directly measured SNR instead of directly measuring the SINR in consideration of the offset affecting the SINR of the client.

)는 95%가 1dB 이하이고, 최대 평가 에러가 1.65dB인 것을 알 수 있다. 따라서, 복수의 기지국들 각각의 SNR에 기초하여 복수의 기지국들 각각의 SINR이 추정되는 과정에서 평가 에러는 무시될 수 있다.In addition, referring to (c), an estimation error CDF (SINR) of each of a plurality of base stations estimated based on the SNR of each of a plurality of base stations

), 95% is 1dB or less, and the maximum evaluation error is 1.65dB. Thus, the evaluation error can be ignored in the process of estimating the SINR of each of the plurality of base stations based on the SNR of each of the plurality of base stations.

The multi-cell beamforming system according to an exemplary embodiment may use a plurality of base stations and a plurality of clients' utilities related to the throughput of each of a plurality of clients based on the estimated SINR according to the method (hereinafter, A beam and a plurality of clients of a plurality of base stations are connected integrally by applying a CABS (Joint Client Association and Beam Selection) algorithm so that a plurality of clients and a whole network utility consisting of a plurality of clients are maximized. .

For example, the multi-cell beamforming system may maximize the utility of a plurality of base stations and a plurality of clients by modeling the average throughput of the client as shown in Equation (3).

&Quot; (3) "

는 모든 기지국들의 빔 선택 벡터를 나타내고,

는 모든 클라이언트들의 연결 벡터를 나타낸다(클라이언트 j가 기지국

와 연결되면

이고, 그 외에는 0임). 또한,

는 빔 구성

아래 기지국

와 연결되었을 때의 클라이언트 j의 평균 처리량을 나타내고,

는 복수의 클라이언트들 각각의 처리량과 관련된 복수의 기지국들 및 복수의 클라이언트들의 유틸리티를 나타낸다.In Equation 3, K and S denote the clients and a set of small cell base stations, respectively. Also,

Denotes a beam selection vector of all base stations,

Denotes a connection vector of all clients (client j is a base station

Once connected

, Otherwise 0). Also,

Beam configuration

Lower base station

Represents the average throughput of the client j when it is connected to < RTI ID = 0.0 >

Represents a utility of a plurality of base stations and a plurality of clients associated with the throughput of each of a plurality of clients.

의 SINR에 의존한다. 복수의 기지국들 각각의 SINR을 기초로 복수의 클라이언트들 각각의 처리량과 관련된 복수의 기지국들 및 복수의 클라이언트들의 유틸리티를 최대화시키는 CABS 알고리즘에 대한 상세한 설명은 도 4를 참조하여 기재하기로 한다.
The utilities of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients thus defined may be such that the base station

Lt; / RTI > A detailed description of the CABS algorithm for maximizing the utility of a plurality of base stations and a plurality of clients related to the throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations will be described with reference to Fig.

4 is a diagram illustrating a CABS algorithm according to an embodiment.

4, a multi-cell beamforming system according to an exemplary embodiment of the present invention applies a CABS algorithm to maximize the utility of a plurality of base stations and a plurality of clients related to a throughput of each of a plurality of clients, Beam and a plurality of clients, respectively.

In particular, a multi-cell beamforming system may be configured such that a plurality of base stations and a plurality of clients associated with the throughput of each of the plurality of clients are maximized based on the SINR of each of the plurality of base stations, An initial connection can be established for each of a plurality of clients.

을 각각 이용하는 경우에 이웃하는 기지국의 스몰 셀에 대한 평균 클라이언트 SNR

을 입력하여(line 1), 간섭이 존재하는 경우 또는 간섭이 존재하지 않는 경우의 평균 클라이언트의 속도를 획득하여, 스몰 셀 부트스트랩 빔을 구성한다(line 3-12). 이 때, 멀티 셀 빔포밍 시스템은 스몰 셀 각각에 대해 간섭이 존재하지 않는 경우의 최상의 유틸리티(복수의 클라이언트들 각각의 처리량과 관련된 복수의 기지국들 및 복수의 클라이언트들의 유틸리티)를 나타내는 복수의 기지국들 각각의 초기 빔을 수학식 4와 같이 설정하고, 모든 활성 클라이언트들이 잠재적으로 빔과 연관될 수 있다고 가정하여 복수의 클라이언트들 각각의 초기 연결을 설정할 수 있다. 여기서, 멀티 셀 빔포밍 시스템은 복수의 클라이언트들 각각의 처리량과 관련된 복수의 기지국들 및 복수의 클라이언트들의 유틸리티가 최대화되도록 복수의 클라이언트들 각각의 처리량과 관련된 복수의 기지국들 및 복수의 클라이언트들의 유틸리티를 적어도 한번 이상의 횟수 동안 반복하여 계산할 수 있다(line 6-10).For example, in a multi-cell beamforming system, a plurality of base stations may transmit different beams

The average client SNR for the small cell of the neighboring base station

(Line 1) to obtain the average client speed in the presence of interference, or in the absence of interference, to construct a small cell bootstrap beam (line 3-12). At this time, the multi-cell beamforming system has a plurality of base stations (not shown) representing the best utility (utility of a plurality of base stations and a plurality of clients associated with the throughput of each of a plurality of clients) Each initial beam can be set as in Equation 4 and an initial connection can be established for each of the plurality of clients assuming that all active clients are potentially associated with the beam. Here, the multi-cell beamforming system includes a plurality of base stations and a plurality of clients' utilities associated with the throughput of each of the plurality of clients so that utilities of a plurality of base stations and a plurality of clients associated with the throughput of each of the plurality of clients are maximized It can be calculated repeatedly for at least one time (line 6-10).

At this time, since a plurality of base stations and a plurality of clients' utilities related to the throughput of each of a plurality of clients among a plurality of clients may have a value smaller than zero, the multi-cell beamforming system may be configured so that a plurality A client with a scheduling and throughput that does not make a positive contribution to the utility so that the utility of a plurality of base stations and a plurality of clients associated with the throughput of each of the clients of the client may have a positive incremental value 7).

&Quot; (4) "

아래 기지국

와 연결되었을 때의 클라이언트 j의 평균 처리량인

는 스케쥴링 방식에 의존되기 때문에, 수학식 5와 같이 표현될 수 있다.
In Equation (4), beam configuration

Lower base station

The average throughput of client j when connected to

Is dependent on the scheduling method, it can be expressed as Equation (5).

Equation (5)

In addition, the incremental utility for proportional fairness can be expressed as Equation (6).

&Quot; (6) "

As described above, after setting the initial beam of each of the plurality of base stations and the initial connection of each of the plurality of clients, the multi-cell beamforming system may update the initial beam of each of the plurality of base stations by disturbing them.

Thus, the multi-cell beamforming system is configured to maximize the utility of a plurality of base stations and a plurality of clients associated with the throughput of each of the plurality of clients based on the initial beam of each of the updated plurality of base stations, (Line 15-20) and then determine the beam of each of the plurality of base stations based on the connection of each of the plurality of clients (line 23) (accordingly, the beam of each of the plurality of base stations also includes a plurality of clients The utility of a plurality of base stations and a plurality of clients associated with each throughput may be determined to be maximized). The process of determining the beam of each of the plurality of base stations may be sequentially performed in each of the plurality of base stations.

In particular, a multi-cell beamforming system includes a plurality of base stations and a plurality of clients' utilities associated with the throughput of each of a plurality of clients to maximize the utility of a plurality of base stations and a plurality of clients associated with the throughput of each of the plurality of clients It can be repeatedly calculated at least once more times (line 17).

Also, since the utility of a plurality of base stations and a plurality of clients associated with the throughput of each of a plurality of clients among a plurality of clients may have a value less than zero, the multi-cell beamforming system may include a plurality of clients Clients with scheduling and throughput that do not make a positive contribution to the utility so that utilities of a plurality of base stations and a plurality of clients associated with throughput of each of the clients have a positive increment value (line 18).

In addition, the multi-cell beamforming system may compare the number of times it is repeatedly calculated so as to maximize the utility of a plurality of base stations and a plurality of clients related to the throughput of each of the plurality of clients, (Line 19) to determine the connection of each of the plurality of clients based on a result of comparing a predetermined threshold with a utility of a plurality of base stations and a plurality of clients associated with throughput. Accordingly, the multi-cell beamforming system may not fall into an infinite loop in the process of determining the connection of each of the plurality of clients.

The multi-cell beamforming system, as described above, after the beam of each of the plurality of base stations and the connection of each of the plurality of clients is determined, a beam of each of the plurality of base stations and a plurality of clients Can perform scheduling for frames transmitted and received. For example, a multi-cell beamforming system notifies each of a plurality of base stations of a determined beam and a client connection, and performs scheduling for frames transmitted and received by each of a plurality of base stations while applying the determined beam to each of a plurality of base stations Can be performed.

As described above, the multi-cell beamforming system integrally determines the beam of each of the plurality of base stations and each of the plurality of clients, and determines a beam of each of the plurality of base stations, By performing the process separately from the scheduling process for the frame, it is possible to improve the beamforming speed as compared with the conventional scheme, to prevent the orthogonal spectrum resource from being wasted, and to handle the interference between the small cells in the spatial domain.

5 is a flowchart illustrating a multi-cell beamforming method according to an embodiment.

Referring to FIG. 5, a multi-cell beamforming method according to an embodiment is performed by a multi-cell beamforming system. Here, the multi-cell beamforming system may be a separate server included in an OFDMA-based small cell network including a plurality of base stations and a plurality of clients. However, the present invention is not limited thereto, and a multi-cell beamforming system may be provided in at least one base station among a plurality of base stations.

The multi-cell beamforming system estimates SINR (Signal to Interference plus Noise Ratio) of each of a plurality of base stations based on a signal to noise ratio (SNR) of each of a plurality of base stations (510).

In this case, the multi-cell beamforming system measures the SNR of each of the plurality of base stations, and then calculates the SINR of each of the plurality of base stations based on the SNR of each of the plurality of base stations, Can be estimated. Here, the fact that the SNR of each of the plurality of base stations is measured may mean that the average SNR for the beams formed by each of the plurality of base stations is measured.

The multi-cell beamforming system then applies a Joint Alliance Association and Beam Selection (CABS) algorithm based on the SINR of each of the plurality of base stations to determine a plurality of base stations and a plurality of clients A beam of each of the plurality of base stations and a connection of each of the plurality of clients are determined to maximize the utility (520).

Specifically, in step 520, the multi-cell beamforming system calculates the SINR of each of the plurality of base stations so that the utilities of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients are maximized And then updating the initial beam of each of the plurality of base stations so that the throughput of each of the plurality of clients based on the initial beam of each updated plurality of base stations, Determine the connection of each of the plurality of clients so that utilities of the associated plurality of base stations and the plurality of clients are maximized and determine the beam of each of the plurality of base stations based on the connection of each of the plurality of clients.

At this time, in the process of setting the initial beam of each of the plurality of base stations and each of the plurality of clients, the multi-cell beamforming system includes a plurality of base stations related to the throughput of each of the plurality of clients, And the utility of the plurality of clients has a positive incremental value.

In addition, the multi-cell beamforming system repeatedly performs at least one or more times to maximize the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients in the process of determining connection of each of the plurality of clients Can be calculated.

Further, in the process of determining the connection of each of the plurality of clients, the multi-cell beamforming system may calculate the plurality of base stations and the utility of the plurality of clients related to the throughput of each of the plurality of clients to have a positive increment value .

Also, in the process of determining the connection of each of the plurality of clients, the multi-cell beamforming system calculates the number of times that the plurality of base stations and the plurality of clients related to the throughputs of the plurality of clients are repeatedly calculated, Stopping determining the connection of each of the plurality of clients based on a result of comparing the set repetition times or comparing a preset threshold value with a utility of a plurality of base stations and a plurality of clients related to the throughput of each of the plurality of clients, can do.

Although not shown in the figure, the multi-cell beamforming system determines the beam of each of the plurality of base stations and the connection of each of the plurality of clients, and then, based on the beam of each of the plurality of base stations and each of the plurality of clients, And perform scheduling for frames transmitted and received by each of the plurality of base stations.

6 is a block diagram illustrating a multi-cell beamforming system in accordance with one embodiment.

6, a multi-cell beamforming system according to an embodiment includes an estimation unit 610 and a determination unit 620. [

The estimator 610 estimates SINR (Signal to Interference plus Noise Ratio) of each of the plurality of base stations based on the SNR (Signal to Noise Ratio) of each of the plurality of base stations.

At this time, the estimator 610 measures the SNR of each of the plurality of base stations, and then calculates the SINR of each of the plurality of base stations based on the SNR of each of the plurality of base stations, Can be estimated. Here, the fact that the SNR of each of the plurality of base stations is measured may mean that the average SNR for the beams formed by each of the plurality of base stations is measured.

The decision unit 620 applies a Joint Alliance Association and Beam Selection (CABS) algorithm based on the SINR of each of the plurality of base stations to maximize the utility of a plurality of base stations and a plurality of clients related to the throughput of each of the plurality of clients So as to determine the beam of each of the plurality of base stations and the connection of each of the plurality of clients.

Specifically, the determination unit 620 determines the initial beam of each of the plurality of base stations so that the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients is maximized based on the SINR of each of the plurality of base stations. Establishing an initial connection of each of the plurality of clients, updating an initial beam of each of the plurality of base stations, determining, based on the initial beam of each of the updated plurality of base stations, And determine the connection of each of the plurality of clients so that the utility of the plurality of clients is maximized, and determine the beam of each of the plurality of base stations based on the connection of each of the plurality of clients.

At this time, in the process of establishing the initial connection of each of the plurality of clients and the initial beam of each of the plurality of base stations, the determination unit 620 may determine, for each of the plurality of clients, And the utility of the plurality of clients has a positive incremental value.

In addition, the determining unit 620 may repeatedly perform at least one or more times to maximize the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients in the process of determining the connection of each of the plurality of clients Can be calculated.

Further, in the process of determining the connection of each of the plurality of clients, the determination unit 620 may calculate the plurality of base stations and the utility of the plurality of clients related to the throughput of each of the plurality of clients to have a positive increment value .

The determining unit 620 determines the number of times that the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients are repeatedly calculated so as to maximize the utility, Stopping determining the connection of each of the plurality of clients based on a result of comparing the set repetition times or comparing a preset threshold value with a utility of a plurality of base stations and a plurality of clients related to the throughput of each of the plurality of clients, can do.

In addition, although not shown in the figure, the multi-cell beamforming system determines the beam of each of the plurality of base stations and the connection of each of the plurality of clients in the determining unit 620, And a scheduler for performing scheduling for a frame transmitted and received by each of the plurality of base stations based on the connection of each of the plurality of base stations.

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, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a 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 unit 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 , Or may be permanently or temporarily embodied in a transmitted signal wave. 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. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

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 (16)

A multi-cell beamforming method in a small cell network based on OFDMA (Orthogonal Frequency Division Multiple Access)
Measuring a signal to noise ratio (SNR) of each of a plurality of base stations in a multi-cell beamforming system, and estimating a signal to interference plus noise ratio (SINR) of each of the plurality of base stations based on the measured SNR ; And
A plurality of base stations and a plurality of clients associated with a throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations in the multi-cell beamforming system, ) Algorithm to determine a beam of each of the plurality of base stations and a connection of each of the plurality of clients
Lt; / RTI >
Wherein determining the connection of each of the plurality of clients comprises:
Wherein the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients exclude clients that do not make a positive contribution to the utility so that the utility of the plurality of clients has a positive increment value, Multi-cell beamforming method for computing utility of clients. The method according to claim 1,
Wherein determining the beam of each of the plurality of base stations and the connection of each of the plurality of clients comprises:
The initial beam of each of the plurality of base stations and the plurality of clients to maximize the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations. Establishing an initial connection for each of the plurality of terminals;
Updating an initial beam of each of the plurality of base stations;
Determining a connection of each of the plurality of clients to maximize a utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients based on an initial beam of each of the updated plurality of base stations step; And
Determining a beam of each of the plurality of base stations based on a connection of each of the plurality of clients
/ RTI > delete 3. The method of claim 2,
Wherein determining the connection of each of the plurality of clients comprises:
Repeatedly calculating at least one or more times so that the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients is maximized
/ RTI > delete 3. The method of claim 2,
Wherein determining the connection of each of the plurality of clients comprises:
The number of times that the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients is maximized and the number of iterations calculated is compared with a preset number of iterations, Stopping determining a connection of each of the plurality of clients based on a result of comparing a predetermined threshold with a utility of the plurality of base stations and the plurality of clients
Wherein the multi-cell beamforming method further comprises: delete The method according to claim 1,
Wherein measuring the SNR of each of the plurality of base stations
Measuring an average SNR for beams formed by each of the plurality of base stations
/ RTI > The method according to claim 1,
Performing a scheduling for a frame transmitted and received by each of the plurality of base stations based on a beam of each of the plurality of base stations and a connection of each of the plurality of clients in the multi-cell beamforming system
Wherein the multi-cell beamforming method further comprises: A computer-readable recording medium having recorded thereon a program for performing the method according to any one of claims 1, 2, 4, 6, 8 to 9. In a multi-cell beamforming system in a small cell network based on OFDMA (Orthogonal Frequency Division Multiple Access)
An estimator for measuring a signal to noise ratio (SNR) of each of a plurality of base stations and estimating a signal to interference plus noise ratio (SINR) of each of the plurality of base stations based on the measured SNR; And
Applying a CABS (Joint Client Association and Beam Selection) algorithm to maximize the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations, A determination unit for determining a beam of each of the base stations and a connection of each of the plurality of clients,
Lt; / RTI >
The determination unit
Wherein the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients exclude clients that do not make a positive contribution to the utility so that the utility of the plurality of clients has a positive increment value, A multi-cell beamforming system for computing the utility of clients. 12. The method of claim 11,
The determination unit
The initial beam of each of the plurality of base stations and the plurality of clients to maximize the utility of the plurality of base stations and the plurality of clients associated with the throughput of each of the plurality of clients based on the SINR of each of the plurality of base stations. And to update the initial beam of each of the plurality of base stations based on the initial beam of each of the updated plurality of base stations, wherein the plurality of base stations associated with the throughput of each of the plurality of clients, And determining a beam of each of the plurality of base stations based on a connection of each of the plurality of clients to determine a connection of each of the plurality of clients so that utilities of the plurality of clients are maximized, system. delete 13. The method of claim 12,
The determination unit
And repeatedly calculates at least one or more times to maximize utility of the plurality of base stations and the plurality of clients associated with throughput of each of the plurality of clients. 13. The method of claim 12,
The determination unit
The number of times that the utility of the plurality of base stations and the plurality of clients related to the throughput of each of the plurality of clients is maximized and the number of iterations calculated is compared with a preset number of iterations, And stops determining the connection of each of the plurality of clients based on a result of comparing the utility of the plurality of base stations and the plurality of clients with a preset threshold value. 12. The method of claim 11,
A scheduler for performing scheduling on a frame transmitted and received by each of the plurality of base stations based on a beam of each of the plurality of base stations and a connection of each of the plurality of clients,
Wherein the multi-cell beamforming system further comprises:

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