KR101531518B1 - Power control method of cooperative base station and base station device using the same - Google Patents

Abstract

A base station cooperative power control method and a base station apparatus for performing the same are disclosed. The first receiving unit receives the token value information indicating the average rate of the specific terminal and the current average rate of satisfaction of the specific terminal from the specific terminal located at the cell boundary of the specific base station in the cooperating unit. The second receiving unit may include an average transmission rate of a mobile station located at a cell boundary of each base station from one or more other base stations in the cooperative unit, a token value of the mobile station located at a cell boundary of each base station, and a current power level of each of the one or more other base stations. And the like. The first power level operation unit guarantees a minimum average transmission rate of a terminal located at a cell boundary of each base station using the minimum average transmission rate and token value information of a terminal located at a cell boundary between the specific terminal and one or more other base stations in the cooperative unit And calculates a first power level vector of each base station in the cooperative unit. The second power level calculator calculates a second power level vector, which is an updated power level of each base station in the cooperative unit, in consideration of the current power level and the first power level of each base station.

Base station cooperative power control, cell boundary

Description

TECHNICAL FIELD [0001] The present invention relates to a base station cooperative power control method, and a base station apparatus using the same.

The present invention relates to a method of controlling power in cooperation with a base station and a base station apparatus using the same.

In a conventional downlink multiple cellular communication system sharing the same frequency resources, bases do not correlate other base stations, but determine the base station power within a given base station maximum power, taking into consideration only the channel states of the terminals belonging to each base station. Respectively.

However, there is a problem in a system in which the frequency reusability is 1, in which the power of the base station is allocated using this conventional scheme. That is, when the terminal is located at a cell boundary away from the base station, the power of the signal is lowered due to the signal attenuation depending on the distance of the radio channel environment, and the communication performance is greatly deteriorated by interference signals from other base stations Lt; / RTI > Thus, a terminal located at a cell boundary (hereinafter, abbreviated as a cell boundary terminal) is difficult to receive a high quality communication service.

In order to overcome these problems, researches on how to collaborate with each other are actively conducted. Managing radio resources through cooperation between cells can help to provide better communication services to cell edge terminals. However, the inter-cell cooperation method requires excessive information exchange between the base stations through a backhaul and a high complexity calculation amount. Therefore, there is a desperate need to study an algorithm having an achievable amount of information exchange and a low complexity suited thereto.

 In the downlink, the interference signal to the neighboring base station is most influential on the performance of the UE. Since an important factor that constitutes the interference signal affecting the UE is the power used by the adjacent base station, it is very important to control the power of the neighboring cell base station not only for the cell edge but also for improving the performance of the entire system.

 As a technique for this, a method for adjusting transmission power in a conventional cellular mobile communication system has been discussed. This relates to a method for adjusting transmission power for increasing the fairness between adjacent base stations in a cellular mobile communication system. The conventional method divides the reception result of the traffic transmitted to each of the base stations into the ACK signal and the NACK signal by each base station and receives the received ACK signal and the NACK signal again from the terminals. Based on the ratio of the NACK signal to the total traffic, The base station having the highest occurrence frequency of the NACK signal transmits the signal with the maximum possible power and conversely the base station with the smallest NACK signal ratio transmits the signal with the smallest possible power.

The NACK signal ratio of each base station is shared with neighboring base stations, and a method for improving inter-cell fairness by reducing the size of interference signals generated from neighboring base stations through negotiation between adjacent base stations has been proposed. That is, according to the prior art, the base station calculates the next transmission power with the transmission power transmission coefficient calculated by each base station according to the transmission success or failure of the data transmitted to the terminal, and exchanges the information with the adjacent base station, To ensure fairness between the two.

In the prior art, in an actual communication environment, the data is coded according to a given channel condition and is transmitted. At this time, a coding rate plays an important role in determining whether data transmission is successful or not. However, the success or failure of the data depends on how the coding rate is appropriately determined according to the channel condition, and it is not suitable for the actual communication environment to evaluate the fairness based on the success or failure of each cell.

In addition, if the communication system satisfying the minimum average transmission rate of the terminals is considered, the above-mentioned condition can not be satisfied by the conventional method. In the conventional technique, even if the data transmission success or failure is a criterion for evaluating the fairness of a cell, a method of lowering the power of an adjacent cell based on a bad cell when negotiating between cells There arises a problem of reducing the maximum power of the adjacent cell which does not need to regulate the power in the taking-in.

Since the degree of interference of neighboring cells with their terminals differs according to the geographical location of the terminals, if it is possible to distinguish a cell which is highly interfering with itself, It is much more efficient than reducing it.

Therefore, the conventional scheme limits the power of neighboring cells that do not greatly interfere with itself, thereby restricting the average transmission rate of the corresponding cell, which causes a problem in that the performance of the entire system is degraded. That is, the negotiation based on the result of calculation by each base station is basically required to be carried out in consideration of various things while sharing information on each other as much as possible. In the above conventional technology, Since the information composed only of information is processed and negotiated, it becomes impossible to know the other base station information, and it becomes impossible to negotiate correctly.

 Thus, the conventional technologies have various problems. Up to now, it has been possible to maximize the fairness among the cells in the downlink multi-cellular system, in particular, the minimum average transmission rate of the cell edge terminals, And a base station apparatus for performing the power control method have not been proposed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a base station cooperative power control method.

According to another aspect of the present invention, there is provided a base station apparatus for performing a base station cooperative power control method.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method of controlling a base station cooperative power, the method comprising: receiving, from a specific terminal located at a cell boundary of a specific base station in the cooperative unit, Receiving token value information indicating an average rate satisfactory degree; An average rate of a terminal located at a cell boundary of each base station from one or more other base stations in the cooperative unit, a token value of a terminal located at a cell boundary of each base station, and a current power level of each of the one or more other base stations ; A minimum average transmission rate and a token value information of a terminal located at a cell boundary between the specific terminal and one or more other base stations in the cooperative unit are used to guarantee a minimum average transmission rate of a terminal located at a cell boundary of each base station, ≪ / RTI > And calculating a second power level vector that is a renewed power level of each base station in the cooperative unit in consideration of the current power level and the first power level of each base station.

According to another aspect of the present invention, there is provided a base station apparatus in which a specific base station in a cooperative unit receives an average transmission rate of a specific terminal and a minimum average transmission rate A first receiving unit for receiving token value information indicating a degree of satisfaction; An average rate of a terminal located at a cell boundary of each base station from one or more other base stations in the cooperative unit, a token value of a terminal located at a cell boundary of each base station, and a current power level of each of the one or more other base stations A second receiving unit for receiving the first signal; A minimum average transmission rate and a token value information of a terminal located at a cell boundary between the specific terminal and one or more other base stations in the cooperative unit are used to guarantee a minimum average transmission rate of a terminal located at a cell boundary of each base station, A first power level calculator for calculating a first power level vector of the first power level; And a second power level calculator for calculating a second power level vector, which is an update power level of each base station in the cooperative unit, in consideration of the current power level and the first power level of each base station.

According to the present invention, the base station power can be controlled by considering the inter-cell interference and calculating the base station power satisfying the minimum average transmission rate and the proportional fairness.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended drawings is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details for a better understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, in the following description, certain terms are mainly described, but they need not be limited to these terms, and they may have the same meaning when they are referred to as arbitrary terms. Further, the same or similar elements throughout the present specification will be described using the same reference numerals.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

The techniques described below may be used in various communication systems, which may provide various communication services such as voice, packet data, and so on. The technology of the communication system can be used for a downlink or an uplink. A base station may be replaced by terms such as a fixed station, a base station, a Node B, an eNode B (eNB), an access point, ABS, In addition, a mobile station (MS) can be replaced with terms such as a UE (User Equipment), a Subscriber Station (SS), a Mobile Subscriber Station (MSS), an AMS or a Mobile Terminal.

Also, the transmitting end refers to a node that transmits data or voice service, and the receiving end refers to a node that receives data or voice service. Therefore, in the uplink, the terminal may be the transmitting end and the base station may be the receiving end. Similarly, in the downlink, the terminal may be the receiving end and the base station may be the transmitting end.

The terminal of the present invention may be a PDA (Personal Digital Assistant), a cellular phone, a PCS (Personal Communication Service) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA) Can be used.

Embodiments of the present invention may be implemented in at least one of the Institute of Electrical and Electronics Engineers (IEEE) 802 systems, 3GPP systems, 3GPP LTE (Third Generation Partnership Project Long Term Evolution) systems and 3GPP2 systems It can be supported by standard documents. That is, the steps or portions of the embodiments of the present invention that are not described in order to clearly illustrate the technical idea of the present invention can be supported by the documents. In addition, all terms disclosed in this document may be described by the standard document. In particular, embodiments of the present invention may be supported by documents such as TS25, TS36 series and C.S000x series, which are standard documents of 3GPP and 3GPP2 systems.

It is to be understood that the specific terminology used herein is for the purpose of enhancing the understanding of the present invention, and the use of such specific terminology may be changed into other forms without departing from the spirit of the present invention.

The term base station as used in the present invention can be used as a concept including a cell or a sector. Also, a higher system corresponds to a system that performs the upper functions of each base station and controls the transmission of data and control information. Such an upper system is generally referred to as a single network entity. The serving base station (cell) can be regarded as a base station providing an existing main service to the mobile station, and can perform transmission and reception of control information on the cooperative multi-transmission point. In this sense, the serving base station may be referred to as an anchor base station (anchor cell).

Hereinafter, the power control for maximizing the proportional fairness is guaranteed by ensuring the minimum average transmission rate of each terminal in the cooperation unit between the cooperating base stations.

1 is a diagram illustrating a method of exchanging information including an average transmission rate between each base station in a cooperating unit.

Referring to FIG. 1, base stations determined to perform cooperation can exchange information between base stations in two major ways. As shown in FIG. 1 (a), each base station can directly transmit and receive information received from the terminals through a backbone previously connected to neighbor base stations. As shown in (b) of FIG. 1, the upper system that manages and controls each base station can receive information received from each base station from each base station, process it, Can be transmitted. Here, the role of the upper system may be performed by any one of the base stations in the cooperating unit.

In the former scheme, since each base station directly receives information from neighboring cells, each base station can perform the base station cooperative power level control algorithm with the same information. In the latter scheme, the higher-level system receives information from each base station in the cooperating unit, thereby performing a base-station cooperative power level control algorithm.

In case of the former scheme, each base station has an advantage that it can obtain the neighbor cell information quickly, but there is a disadvantage in that each base station loads each cell according to the same inter-cell power level determination algorithm.

On the other hand, in the latter scheme, since each base station hands its own information to the upper system, it is not necessary to directly share the adjacent cell information and only the power information determined by the upper system needs to be received. load is reduced. On the other hand, the time required to calculate the final power level is slightly more than the former method. Since either one of the two methods is not uniformly good, one method suitable for communication and system conditions can be selected and used.

When exchanging information between each base station as in the former scheme, each base station in the cooperative unit can perform base station power control. In addition, any one of the base stations in the cooperating unit may perform the base station cooperative power level control method. When one base station performs the base station cooperative power control method, it can inform the other base stations in the cooperative unit through the signaling result.

Meanwhile, when exchanging information between respective base stations as in the latter scheme, an upper system other than each base station can perform base station cooperative power level control. Even when the upper system controls the base station cooperative power level, only the method of exchanging information between the base stations is different, and the method of controlling the base station cooperative power level can be performed in the same manner as that performed by each base station.

Hereinafter, a process of performing base station cooperative power level control by any of the base stations or the cooperating unit base stations in the cooperating unit will be described with reference to the former scheme. The process of the base station performing the base station cooperative power control is the same as that performed by the base station in the configuration thereof, and thus description thereof will be omitted.

In the present invention, the base station in the cooperating unit may be newly configured according to a predetermined cycle for determining the cooperation unit between the base stations. Depending on the cooperative unit decision cycle, it is possible to determine the cooperating unit to perform cooperation between the base stations. The base stations in the determined cooperation unit can exchange mutual information.

2 is a block diagram illustrating a configuration of a preferred embodiment of a base station apparatus 200 that performs base station cooperative power level control according to the present invention.

2, a base station apparatus for performing base station cooperative power level control according to the present invention includes a cell boundary terminal determination unit 210, a transmission unit 220, a reception unit 230, a first power level calculation unit 240, 2 power level calculator 250. [

)으로 구성될 수 있다. 셀 경계에 위치한 하나의 단말을 선택하는 방식을 이용함으로써 백본을 통한 데이터 전송량을 크게 줄일 수 있는 효과가 있다. The cell boundary terminal determination unit 210 selects one terminal for each cell when information is shared among the base stations. These cell edge terminals are referred to as a set (

). A method of selecting one terminal located at a cell boundary is used, thereby greatly reducing the data transmission amount through the backbone.

The cell boundary terminal determination unit 210 can freely select a cell boundary terminal by adjusting each base station within a cooperation period between the base stations. At this time, the period for selecting a cell boundary terminal may be a value including a period for exchanging information between a plurality of cells. The information exchange period between the base stations may be one frame or a unit including a plurality of frames. That is, after the cooperation unit between the base stations is determined, the cell boundary terminal can be selected several times according to the needs of the base stations cooperating within the cycle of selecting the cell boundary terminal, and the information of the selected cell boundary terminal includes one or more frame units It can be transmitted and received every cycle.

The base station cooperative power control method according to the present invention to be described below can be performed with the same period as the information exchange period between the base stations. Here, the cooperative unit is predetermined and it is assumed that the information between the base stations is already shared.

Hereinafter, a criterion for each base station to select a cell boundary terminal will be described.

First, the cell boundary terminal determination unit 210 can select a terminal having the smallest average channel value from the serving base station. A criterion for the base station b to select a cell boundary terminal may be expressed as Equation 1 below.

는 기지국 b 및 기지국 b의 k번째 단말 간의 평균 채널 값이고,

는 기지국 b가 서비스하고 있는 단말들의 집합이다.here

Is an average channel value between the k < th > terminals of the base station b and the base station b,

Is a set of terminals serviced by the base station b.

Secondly, the cell boundary terminal determination unit 210 can select the terminal having the largest sum of interference as the cell boundary terminal. This method assumes that the average channel information is exchanged and shared among the base stations in the cooperation unit in advance. A criterion for the base station b to select a cell boundary terminal may be expressed by the following equation (2).

Where c is the set of base stations in the cooperating unit.

Thirdly, the cell boundary terminal determination unit 210 can select the terminal having the lowest average transmission rate as the cell boundary terminal. The criterion for the base station b to select the cell boundary terminal can be expressed by Equation (3).

는 기지국 b의 k번째 단말의 평균 전송률이다.here

Is the average transmission rate of the k < th >

In the fourth method, the cell boundary terminal determination unit 210 can select the terminal having the largest token value as the cell boundary terminal. The criterion by which the base station b selects the cell boundary terminal can be expressed by Equation (4).

The transmitting unit 220 transmits the average transmission rate of each cell boundary terminal of each base station determined by the above method, the token value indicating the degree to which the cell boundary terminal satisfies the minimum average transmission rate so far and the current base station power level, Or the like.

The receiving unit 230 may receive an average rate and a token value from a terminal located at a cell boundary of the base station. Also, the receiver 230 can receive information including the average data rate, the token value, and the current power level of each base station located at the cell boundary from the other base stations in the cooperative unit.

를 찾는다. 이러한 전력 레벨

는 다음 수학식 5의 메트릭(metric)을 만족하는 벡터값 이다.The first power level calculator 240 may calculate a power level vector of each base station satisfying a minimum average data rate and a proportional fairness of a terminal located at a cell boundary of each base station in a cooperative unit. That is, when the cell information is shared among the base stations, the first power level calculator 240 calculates a power level vector that satisfies the proportional fairness of the cell boundary users while satisfying the minimum average transmission rate of the cell boundary terminals

. These power levels

Is a vector value satisfying the following metric (5).

는 기지국 b의 k번째 단말의 평균 전송률,

는 기지국 b 및 기지국 b의 k번째 단말 간의 평균 채널 값,

는 기지국 b가 서비스하고 있는 단말 집합,

는 셀 경계 단말 집합, a는 토큰 가중(weight) 함수,

는 기지국 b의 k번째 단말의 토큰값,

는 기지국의 최대 전송 전력,

는 잡음의 평균 전력, R_min은 최소 평균 전송률을 나타낸다.here

Is the average transmission rate of the k < th > terminal of the base station b,

Is an average channel value between the k < th > terminals of the base station b and the base station b,

A set of terminals served by the base station b,

Is a set of cell edge terminals, a is a token weight function,

Is the token value of the k < th > terminal of the base station b,

Is the maximum transmission power of the base station,

Is the average power of noise, and _Rmin is the minimum average transmission rate.

를 다음과 같은 방법을 이용하여 찾을 수 있다.At this time, the first base station power calculator 240 calculates the power level

Can be found using the following method.

같이 최대 전력 대비 여러 레벨을 갖는 전력으로 나눈다. 그리고, 제 1 기지국 전력 계산부(240)는 각 기지국 마다 하나의 전력 레벨을 선정하여 상기 수학식 5를 만족하는지 여부를 알아볼 수 있다. 여기서

는 테스트 전력 레벨의 개수이다. 각 기지국의 모든 전력 조합에 대해서 상기 수학식 5의 만족 여부를 알아본 후, 만족하는 조합 중, 상기 수학식 5의 메트릭을 최대로 만드는 전력 조합

를 계산할 수 있다. The first base station power calculation unit 240 calculates a first base station power

Likewise, divide the power into several levels of power relative to the maximum power. The first base station power calculator 240 can determine whether one of the power levels is satisfied for each base station and satisfies Equation (5). here

Is the number of test power levels. After all of the power combinations of the respective base stations are found to satisfy the above Equation (5), among the satisfying combinations, the power combination that maximizes the metric of Equation (5)

Can be calculated.

가 커질수록 상기 수학식 5를 만족하는 전력 조합

를 찾는데 소요되는 시간 및 연산 복잡도가 증가하게 된다. 이와 달리

를 너무 작게 하면, 수학식 5를 만족하는 최적의 전력 조합을 찾지 못할 수도 있다. 따라서, 복잡도와 최적 전력을 고려하여, 적절한 값으로

를 설정하는 것이 바람직하다.At this time

The power combination satisfying Equation (5)

And the complexity of the computation increases. Unlike

The optimum power combination satisfying the expression (5) may not be found. Therefore, considering the complexity and the optimum power,

.

The token value is a concept introduced in a system that performs proportional fair scheduling. To satisfy the minimum average transmission rate condition of the terminal, each token is assigned to the terminals, and the token value is increased as the minimum average transmission rate is not satisfied. Therefore, the mobile stations that do not satisfy the minimum average transmission rate will have a larger token value, which can be reflected in the scheduling, giving more priority to the mobile stations. Whereby the minimum average transmission rate condition of the terminals can be controlled within a possible range.

The token value for the k-th terminal belonging to the base station b can be updated using the following Equation (6).

는 기지국 b 및 기지국 b의 k번째 단말 간의 평균 채널 값을 나타내고,

는 시각 t에서의 순간 전송률로서 다음 수학식 7과 같이 나타낼 수 있다.Where R _min is the minimum average transmission rate,

Represents an average channel value between the k < th > terminals of the base station b and the base station b,

Is an instantaneous transmission rate at time t and can be expressed by Equation (7).

가 존재한다면, 제 2 기지국 전력 계산부(250)는 현재 전력 레벨 및 상기 수학식 5를 만족시키는 기지국 전력 레벨

를 고려하여, 다음 수학식 8과 같이 새로운 기지국 전력 레벨을 계산할 수 있다. 그리고, 이 계산된 새로운 기지국 전력 레벨로 갱신할 수 있다. The base station power level satisfying Equation (5) for power control between the above-

The second base station power calculator 250 calculates the current power level and the base station power level satisfying Equation (5)

The new base station power level can be calculated by Equation (8). Then, it can be updated to the calculated new base station power level.

는 현재 기지국의 전력 레벨을,

는 새로운 기지국 전력레벨을,

는 전력 조절 상수를 나타낸다.

값은 주어진 상황에 따라서 적절히 정할 수 있는 값이다. 예를 들어, 정확하게 최소 평균 전송률 조건을 만족시키는 것을 조금 손해 보더라도, 좀 더 빨리 기지국 간에 공평성(fairness)을 만족시키고 싶다 면,

값을 큰 값으로 사용해야 하며, 이와 달리 인접 기지국과 자신의 기지국이 전력을 조금만 변경시켜도 단말의 평균 전송률이 상대적으로 크게 움직인다면,

값을 작은 것을 사용하여 세밀히 조절하여 단말의 최소 평균 전송률을 만족시키는 것이 더 바람직할 수 있다.here

The power level of the current base station,

The new base station power level,

Represents the power control constant.

The value is a value that can be set appropriately according to the given situation. For example, if you want to satisfy fairness between base stations more quickly, even if you are a little bit tired of meeting the minimum average rate requirement,

If the neighbor base station and its own base station change the average transmission rate relatively even if the power is slightly changed,

It may be more preferable to satisfy the minimum average transmission rate of the terminal by adjusting it with a small value.

가 존재하지 않는다면, 제 1 기지국 전력 계산부(240)는 다음과 같은 과정을 다시

를 찾을 수 있다. 즉 최소의 토큰 값을 갖는 단말이 속한 셀을 협력 단위에서 잠시 제외하는 방법을 이용할 수 있다. 수학식 9는 최소의 토큰 값을 갖는 단말이 속한 셀을 나타낸다. If Equation 5 is satisfied,

The first base station power calculation unit 240 repeats the following steps

Can be found. That is, a method of temporarily excluding a cell in which a terminal having a minimum token value belongs from a cooperative unit can be used. Equation (9) represents a cell to which a terminal having a minimum token value belongs.

Equation (10) represents a set of base stations that temporarily exclude a cell to which a terminal having a minimum token value belongs from a cooperating unit.

를 찾는다. 이 과정은

를 찾을 때까지 반복할 수 있다. 새로운 토큰 값이 가장 작은 기지국을 선정하여 제외하는 이유는 상대적으로 전송 상황이 좋은 셀보다, 전송 상황이 좋지 않은 다른 셀부터 우선적으로 고려함으로써 조금이라도 더 비례 공평을 만족시키기 위한 것이다. 상기 과정을 수행하다 한 셀만 남게 되면 인접 셀의 간섭을 고려하지 않게 된다는 것이므로, 이때 최적의 전력은 기지국 최대 전력

가 된다.The first base station power calculator 240 calculates the first to fourth power calculations using the Equation 5 for the base stations that temporarily excluded the cell to which the terminal having the smallest token value belongs,

. This process

Can be repeated until it is found. The reason for selecting and excluding the base station with the smallest new token value is to satisfy the proportional fairness even slightly by considering the other cells having a bad transmission condition rather than the cell having a relatively good transmission condition. If only one cell is left to perform the above procedure, the interference of the neighboring cell is not considered, and the optimal power is the maximum power of the base station

.

3 is a diagram showing an embodiment of a preferred packet data structure for transmitting information exchanged between base stations in a cooperative unit.

3, a method of configuring packet data includes a first packet data configuration scheme, which is a scheme configured in the case where a base station estimates and transmits information corresponding to an average channel value per each BS, There is a second packet data configuration method that is a packet data configuration in the case of transmitting the average signal-to-interference and noise ratio (SINR: Signal Interference to Noise Ratio).

In both cases, a cell ID (Identifier) may be allocated at the beginning of the packet. Since each cell has a unique cell ID in the cellular system, the cell ID information is information used to identify which cell the information is from on the receiving side. In addition, the current power level information used by the base station of the corresponding cell, the average channel value or the average signal-to-interference and noise ratio information per each base station of the terminal before transmission from each base station, the average transmission rate and the token value to the present can be assigned have. Here, | C | is the total number of base stations constituting the cooperation unit C. The packet data may be directly transmitted to an adjacent cell or transmitted to an upper system according to a neighbor cell information exchange scheme.

4 is a flowchart illustrating a method of controlling a base station cooperative power level according to an exemplary embodiment of the present invention.

)으로 구성될 수 있다. 이러한 선택된 셀 경계 단말의 평균 전송률 및 토큰 값을 포함하는 정보를 수신하는 방법을 이용함으로써 백본망을 통한 데이터 전송량을 감소시켜 백본망의 과부하를 방지할 수 있다.Referring to FIG. 4, the cell boundary terminal determination unit 210 selects one terminal located at the cell boundary of the base station (S410). As described above, the cell boundary terminal determination unit 210 determines whether a cell having the lowest average channel value, a terminal having the largest sum of interference, a terminal having the lowest average transmission rate, and a terminal having the largest token value May be selected as one terminal located at the cell boundary of each base station in the cooperation unit (S410). These cell edge terminals are referred to as a set (

). By using the method of receiving the information including the average transmission rate and the token value of the selected cell border terminals, it is possible to reduce the data transmission amount through the backbone network, thereby preventing the backbone network from being overloaded.

The transmitting unit 220 may transmit to the other base stations in the cooperating unit the average transmission rate of the cell boundary mobile stations of the selected base stations, the token value indicating the degree of satisfaction of the minimum average transmission rate of the mobile station until now, and the current base station power level S420).

The receiving unit 230 may receive information including the average data rate, the token value, and the current power level of each base station located at a cell boundary for each base station from other base stations in the cooperating unit (S430).

를 찾는다. 이러한 전력 레벨 벡터

는 상기 수학식 5를 만족하는 벡터값이다.The first power level calculator 240 may calculate a power level vector of each base station that satisfies a minimum average data rate and a proportional fairness of a terminal located at a cell boundary of each base station in a cooperative unit at step S440. That is, when the cell information is shared among the base stations, the first power level calculator 240 calculates a power level vector that satisfies the proportional fairness of the cell boundary users while satisfying the minimum average data rate of the cell boundary terminals

. These power level vectors

Is a vector value satisfying Equation (5).

Thereafter, the second power level calculator 250 calculates a new power level vector of each base station using the current power level of each base station and the power level vector that satisfies Equation 5 calculated by the first power level calculator 240, (S450). Thereafter, the second power level calculator 250 may update the new base station power level vector with a second power level vector to be used by each base station (S460).

The base station can then transmit one or more of the first power level vector and the second power level vector information to the other base stations in the cooperating unit.

5 is a diagram illustrating an example of an algorithm for controlling a base station cooperative power level according to the present invention.

Referring to FIG. 5, each base station can determine whether there is a cell boundary terminal that does not satisfy the minimum average transmission rate (S510). That is, each base station can determine whether or not to change the currently used power. The indicator used here is whether or not the average transmission rate of each terminal satisfies the minimum average transmission rate condition. If the average transmission rate of all cell boundary terminals satisfies the minimum average transmission rate condition, the current power level of each base station is maintained. If at least one terminal that does not meet the minimum average rate requirement is present, the current power level between the base stations needs to be modified.

The first power level calculator 240 may calculate the base station power level satisfying the minimum average transmission rate of the terminal using Equation (5) (S520). Thereafter, the first power level calculator 240 may determine whether a base station power level satisfying Equation 5 exists (S530).

If there is a power level that satisfies the minimum average transmission rate of all cell boundary terminals, the second power level calculator 240 can calculate a new base power level using Equation (8) The power level can be updated (S540). Alternatively, if there is no power level that meets the minimum average transmission rate of all the cell boundary terminals, one of the cooperating cells is dropped and the remaining base station information is used to determine the optimal power level 3 power level vector may be calculated (S550).

If only one cell is left after performing the above procedure, the interference of the adjacent cell is not considered, so that the optimal power can be the maximum power of the base station at this time. The base station can then transmit the third power level vector information to the other base stations in the cooperating unit.

Using the base station power information calculated through the above process, each base station can perform proportional fair scheduling considering the power allocated to itself and the power of the adjacent base station, and can select a terminal to receive the service. That is, the power level of the base station considering the cell edge terminal is determined first among the base stations with which cooperation is established, and each base station can perform scheduling considering each neighbor cell interference by using the information at each base station in the future.

So far, we have examined the power control algorithm between BSs for the minimum average data rate in a single subchannel. Hereinafter, a power control algorithm between BSs in a multi-subchannel extended to multiple subchannels will be described.

까지 최대로 전력 할당이 되어있다고 가정한다. 만약, 다중 채널 중 한 부채널에서 실제 사용하는 전력이 사용할 수 있는 최대 전력보다 작게 되는 경우, 채널에서 사용하고 남은 잉여 전력을 다음 부채널의 최대 전력에 더해서 기본적으로 할당된

보다 더 높은 최대 전력을 사용하는 것이 가능하다. In general, a plurality of subchannels can be used by the base station. The sum of power available for a plurality of subchannels is limited to within the maximum power sum of the base stations. Therefore, the power remaining in one subchannel can be used for the next subchannel. Each subchannel is basically

The maximum power allocation is assumed. If the actual power used by one of the multiple channels becomes smaller than the maximum power that can be used, the residual power used by the channel is added to the maximum power of the next subchannel,

It is possible to use a higher maximum power.

6 is a diagram illustrating an example of an inter-base station power control algorithm in which an inter-base station power control algorithm for a minimum average transmission rate in a single sub-channel is extended to multiple sub-channels.

로 초기화되며, 각 부채널을 위한 잉여 전력

도 0으로 초기화된다. 즉,

로 초기화된다(S610). 여기서 s는 부채널 인덱스,

는 협력 단위 내의 기지국들의 최대 전력들을 나타내는 벡터, 그리고

는 s번째 부채널을 위해 사용될 수 있는 각 기지국의 잉여 전력 벡터를 나타낸다.Referring to FIG. 6, the maximum power of each subchannel is

, And the surplus power for each subchannel

0 " In other words,

(S610). Where s is the subchannel index,

Is a vector representing the maximum powers of the base stations in the cooperating unit, and

Represents the residual power vector of each base station that can be used for the s < th > subchannel.

외에 s-1 번째 부채널에서 사용되지 않고 남은 잉여 전력을 더하여 상기 부채널에서 사용될 수 있는 최대 전력을 구할 수 있다(S620). 이는 다음 수학식 11과 같이 나타낼 수 있다.The power already allocated for the s-th subchannel

The remaining power that is not used in the (s-1) th sub-channel may be added to obtain the maximum power that can be used in the sub-channel (S620). This can be expressed by the following equation (11).

는 s번째 부채널에서 사용 가능한 최대 전력레벨을 나타낸다. here

Represents the maximum power level available in the s < th > subchannel.

)(S640), 이와 달리 셀 경계 단말들이 최소 평균 전송률 조건을 만족시키지 못하면, 상기 수학식 5를 만족하는

를 구한다(S650). 이때 부채널 인덱스 s가 1일 때 이용되는

값은 이전 시간의 마지막 N_S번째 부채널에서 사용했던 각 기지국들의 전력값이라고 가정한다. 결과적으로, 시각 t에서 s번째 부채널 을 위한 전력 레벨은 다음 수학식 12를 이용하여 갱신될 수 있다(S660).The BSs in the cooperating unit determine whether their cell boundary terminals satisfy the minimum average rate requirement (S630). If the cell edge terminals satisfy the minimum average transmission rate condition, the current power is used as it is in the previous subchannel (

) (S640). On the other hand, if the cell boundary terminals do not satisfy the minimum average transmission rate condition,

(S650). When the subchannel index s is 1,

Value it is assumed that the power value of each of the base stations that were used in the last N _S-th subchannel of the previous time. As a result, the power level for the s < th > subchannel at time t can be updated by using Equation 12 (S660).

After updating the power level, if the current subchannel is not the last subchannel (S670), the process can be repeated to set the power for the next subchannel of each base station. At this time, the residue power for the next subchannel can be calculated by the following equation (13).

In order to apply Equation (5) to the next subchannel, the corresponding token value and the average transmission rate must be updated. There are two methods of updating the token value and the average transmission rate for the multiple subchannels. (PFS-S, hereinafter referred to as " PFS-S ") method, in which the token value and the average transmission rate used in the previous frame are used as they are (PFS-I, hereinafter referred to as " PFS-I ") in which a token value and an average transmission rate of each cell boundary terminal are updated, I system).

) 및 평균 전송률(

) 갱신은 각각 다음 수학식 15 및 수학식 16에 의하여 계산될 수 있다.In the PFS-I scheme, the power calculation for each subchannel is performed according to the following equation (14), and the token value of the cell boundary terminal for the algorithm at time t

) And average transfer rate

) Can be calculated by the following equations (15) and (16), respectively.

는 시각 t에서의 s번째 부채널의 순간 전송률,

는 기지국 b 및 기지국 b의 k번째 단말 간의 평균 채널 값이다.here

Is the instantaneous transmission rate of the s-th subchannel at time t,

Is an average channel value between the k < th > terminals of the base station b and the base station b.

는 시각 t에서의 s번째 부채널의 전력 레벨, N_S는 전체 부채널의 수이다.here

Is the power level of the s-th subchannel at time t, and N _s is the total number of subchannels.

Meanwhile, in the PFS-S scheme, the update of the token value and the average rate is the same as the update in the single subchannel, so that the description is omitted.

The concept of multi-subchannels coincides with the concept of a sub-band in Orthogonal Frequency Division Multiplexing (OFDM). In the OFDM system, each terminal data can be divided into subchannel units. At this time, a maximum power sum exists for each base station, and the total power allocated to each subchannel can be determined within a range that does not exceed the maximum power sum. have.

In OFDM, after applying the power control algorithm between the BSs for each subchannel, the remaining power can be used to increase the maximum power of the next channel. As a result, in OFDM, which is a multi-channel environment, .

7 is a diagram illustrating a base station and a terminal in a cooperative unit for performing a base station cooperative power level control algorithm according to the present invention.

)는 4를 사용하였고, 셀 반경 D_b는 1km, 그리고 최대 기지국 전력

를 위해 셀 최외곽 지역에 위치한 단말을 위한 신호의 평균 신호대 간섭비(SNR)

를 정의하고(

),

가 10dB가 되도록 각 기지국 전력을 설정한다.Referring to FIG. 7, it is assumed that the experimental environment is a downlink multiple cellular wireless communication network consisting of four tiers, that is, 61 cells. It is assumed that there is one base station at the center of each cell, and three users (terminals) per cell are uniformly distributed per area and all users are waiting for service. The path attenuation index of the signal (

) Was 4, the cell radius D _b was 1 km, and the maximum base station power

The average signal-to-interference ratio (SNR) of a signal for a terminal located in the outermost region of the cell

And

),

The power of each base station is set to be 10 dB.

가 되도록 하여 단말에게 서비스하는‘S-RRM’방식 및 다음 수학식 17을 최대로 할 수 있는 가장 최적의 단말 조합과 그에 해당하는 전력 조합을 일일이 구하여 최대의 셀간 비례 공평성을 얻을 수 있는‘O-CRRM’ 방식을 함께 실험하여 비교하였다. In order to compare the effects of the power control algorithm between the base stations according to the present invention, it is assumed that each base station does not perform inter-cell cooperation, that is,

C-RRM " scheme for maximizing the intra-cell proportional fairness by obtaining the most optimal combination of the terminals and the corresponding power combination that can maximize the following Equation (17) 'Were compared and compared.

This 'O-CRRM' scheme is described in US patent application (US 2007/0248048) filed by C. Zhu, T. Girici, J. Russell A, Quot; PROFOR- STIONAL FAIR SCHEDULER FOR OFDMA WIRELESS SYSTEMS WITH QOS CONSTRAINTS "for an OFDM wireless system with QOS constraints. This Equation (17) The scheduling method that maximizes the sum is dealt with as follows.

는 시각 t에서 기지국 b의 k번째 단말의 스케줄링 여부를 알려주는 지시자(indicator)이며, 스케줄링이 되었으면 1을, 그렇지 않으면 0인 값을 가진다. here

Is an indicator for indicating whether or not scheduling of the k < th > terminal of the base station b at time t is 1, and has a value of 1 if scheduling is performed,

Equation (5) proposed by the present invention is a formula for significantly reducing the complexity of Equation (17) and performing base station power control for satisfying a minimum average transmission rate in consideration of inter-cell interference.

The average transmission rate (bps / Hz) of each terminal and the cumulative distribution function (CDF) were calculated based on the downlink multi-cellular wireless communication network model to be described below, and the effect according to the present invention was measured.

는 정밀도를 고려하여 0.05로 정하였다. 셀 경계 단말의 선택 주기는 셀간 협력이 맺어지는 주기와 동일할 수 있고, 하나의 셀간 협력 주기는 여러 개의 프레임 슬롯으로 구성될 수 있다고 가정한다. 이때, 각 기지국은 매 프레임마다 자신의 셀 경계 단말의 정보를 인접 기지국들과 교환할 수 있다. 매 프레임마다 정보 교환이 이루어지고 나서, 기지국 협력 전력 레벨 제어를 수행한 후, 각 기지국이 사용할 전력 레벨이 결정되면, 각기 비례 공평 스케줄러를 사용하여, 단말에게 서비스한다고 가정한다.At this time, N _P used to find the power level satisfying Equation (5) is set to 4. Also, the power update constant

Was set to 0.05 in consideration of the accuracy. It is assumed that the selection period of the cell edge terminal may be the same as the period in which inter-cell cooperation is established, and that one inter-cell cooperation period may be composed of several frame slots. At this time, each base station can exchange information of its cell boundary terminal with neighboring base stations every frame. After information is exchanged every frame, after the base station cooperative power level control is performed, when the power level to be used by each base station is determined, it is assumed that each terminal uses a proportional fairness scheduler to serve the terminal.

8 is a diagram illustrating a CDF for a final average transmission rate in case of a single subchannel based on a downlink multiple cellular wireless communication network model.

)은 0.3, 신호의 경로 감쇄 지수(

)는 4, 셀 반경 D_b는 1km, 각 셀당 3명의 사용자(단말)(k=3)이며, 토큰 가중 함수 a=1이라고 가정한다. Referring to FIG. 8, the experimental environment is a downlink and a single subchannel, and has four tiers, a minimum average transmission rate

) Is 0.3, the path attenuation index of the signal (

) Is 4, the cell radius D _b is 1 km, three users (terminals) (k = 3) per cell, and a token weighting function a = 1.

Simulation results show that proposed CRRM ('Proposed CRRM') method for applying the base station cooperative power level control algorithm satisfies all minimum average transmission rates of all terminals and 'O -CRRM ' method. ≪ / RTI >

Also, it can be seen that the performance is very superior to the 'S-RRM' scheme in which power control is not performed for each base station. Here, the 'S-RRM' scheme does not satisfy the minimum average transmission rate requirement of 10%. However, it can be seen that the proposed CRRM scheme according to the present invention has a good distribution of resources for each cooperating unit, satisfies the minimum average transmission rate well, and maintains proportional fairness relatively well.

In addition, considering that the complexity is much lowered by the base station cooperative power level control considering the cell boundary terminal as compared with the 'O-CRRM' scheme, the present invention shows a remarkably superior performance.

9 is a diagram illustrating CDFs for a final average transmission rate in the case of multiple subchannels based on a downlink multiple cellular wireless communication network model.

=0.42, 신호의 경로 감쇄 지수(

)는 4, 셀 반경 Db는 1km, 각 셀당 3명의 사용자(단말)(k=3), 토큰 가중 함수 a=1로 설정하고 시뮬레이션한 것이다. Referring to FIG. 9, the experimental environment is a downlink and a single subchannel, and a 4-tier, minimum average transmission rate is relatively high

= 0.42, the path attenuation index of the signal (

) Is 4, the cell radius Db is 1 km, and 3 users (terminals) (k = 3) and a token weighting function a = 1 per cell are simulated.

As the number of subchannels increases from 1 to 4, the S-RRM scheme becomes more and more unaware of the interference situation from adjacent cells. Therefore, if the PFS-I scheme is used, You can see that performance is getting worse.

In contrast, the CRRM scheme proposed in the present invention performs inter-cell cooperation using interference information from neighboring cells, and therefore, it can be seen that the CRRM scheme exhibits better performance at 4 than when the number of subchannels is 1. Therefore, it can be seen that not only a single subchannel but also a wireless cellular system having multiple subchannels such as OFDM have an excellent performance improvement effect.

The embodiments described above are those in which the elements and features of the present invention are combined in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) Field Programmable Gate Arrays), a processor, a controller, a microcontroller, a microprocessor, or the like.

In the case of an implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, a procedure, a function, or the like which performs the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a method of exchanging information including an average transmission rate among respective base stations in a cooperative unit;

2 is a block diagram illustrating a configuration of a preferred embodiment of a base station apparatus for performing base station cooperative power level control according to the present invention;

3 shows an embodiment of a preferred packet data structure for transmitting information exchanged between base stations in a cooperating unit,

FIG. 4 is a flowchart illustrating a process of a base station cooperative power level control method according to a preferred embodiment of the present invention.

5 is a diagram illustrating an example of an algorithm for controlling a base station cooperative power level according to the present invention;

6 is a diagram illustrating an example of an inter-base station power control algorithm in which an inter-base station power control algorithm for a minimum average transmission rate in a single sub-channel is extended to multiple sub-channels,

7 is a diagram illustrating a base station and a terminal in a cooperative unit for performing a base station cooperative power level control algorithm according to the present invention;

8 is a diagram illustrating a CDF for a final average transmission rate in case of a single subchannel based on a downlink multiple cellular wireless communication network model,

9 is a diagram illustrating CDFs for a final average transmission rate in the case of multiple subchannels based on a downlink multiple cellular wireless communication network model.

Claims (20)

A method for cooperatively performing power control in at least two base stations in a cooperating unit, Receiving a token value information indicating a minimum average rate satisfaction degree from a specific terminal located at a cell boundary of the specific base station in the cooperative unit, the average transmission rate of the specific terminal and the present time of the specific terminal; An average rate of a terminal located at a cell boundary of each base station from one or more other base stations in the cooperative unit, a token value of a terminal located at a cell boundary of each base station, and a current power level of each of the one or more other base stations ; A minimum average transmission rate and a token value information of a terminal located at a cell boundary between the specific terminal and one or more other base stations in the cooperative unit are used to guarantee a minimum average transmission rate of a terminal located at a cell boundary of each base station, ≪ / RTI > And Calculating a second power level vector that is a renewed power level of each base station in the cooperating unit in consideration of the current power level of the base station and the first power level. The method according to claim 1, Further comprising transmitting to the other base stations in the cooperative unit information including the average transmission rate of the specific terminal, the token value, and the current power level of the particular base station itself. The method according to claim 1, Wherein a first power level vector of each base station in the cooperative unit is calculated by a metric of Equation A to ensure a minimum average rate of a terminal located at a cell boundary of each base station and a proportional fairness among cells, Cooperative power control method: [Mathematical formula A]

here

Is the average transmission rate of the k < th > terminal of the base station b,

Is an average channel value between the k < th > terminals of the base station b and the base station b,

A set of terminals served by the base station b,

Is a set of cell edge terminals, a is a token weight function,

Is the token value of the k < th > terminal of the base station b,

Is the maximum transmission power of the base station,

Is the average power of noise, and R _min is the minimum average transmission rate. 3. The method of claim 2, The second power level vector

/ RTI > is calculated by: < RTI ID = 0.0 > [Mathematical expression B]

here

Is the current base station power level vector,

Represents the power control constant. The method of claim 3, Wherein the token value is updated using: < EMI ID = [Mathematical expression C]

here

Is the instantaneous transmission rate at time t

R _min is the minimum average transmission rate,

Represents an average channel value between the k < th > terminals of the base station b and the base station b. The method according to claim 1, A minimum average rate of a terminal located at a cell boundary of each base station using a minimum average rate and a token value information of a terminal located at a cell boundary of the remaining base stations excluding a base station having a minimum token value among the base stations in the cooperative unit Further comprising calculating a third power level vector of each base station in the cooperating unit. The method according to claim 6, And transmitting one or more power level vector information of the first to third power level vector information to another base station in the cooperating unit. The method according to claim 1, One of the UEs located at the cell boundary of the base station in the cooperative unit may be any one of the UE having the smallest average channel value, the UE having the largest sum of interference, the UE having the lowest average rate, and the UE having the largest token value In base station cooperative power control method. The method of claim 3, The first power level vector for a particular subchannel

Is calculated by the metric of Equation (A) further comprising unused power not used in a previous subchannel of the particular subchannel. 5. The method of claim 4, The second power level vector for a particular subchannel is calculated by: < EMI ID = [Mathematical expression D]

Where s is the subchannel index,

Is the power control constant, and t is the time. 10. The method of claim 9, Wherein the token value for the particular subchannel is updated using Equation E: (E)

. 10. The method of claim 9, The average transmission rate of the terminal for the specific subchannel

Is calculated by the following equation F: [Mathematical expression F]

Where s is the subchannel index,

Is the total number of subchannels,

Represents the instantaneous transmission rate of the s-th subchannel at time t. A base station apparatus for performing power control in cooperation with a base station in a cooperative unit, A first receiving unit for receiving token value information indicating a minimum average rate satisfactory degree from a specific terminal located at a cell boundary of the specific base station in the cooperative unit to an average transmission rate of the specific terminal and a current average rate of the specific terminal; An average rate of a terminal located at a cell boundary of each base station from one or more other base stations in the cooperative unit, a token value of a terminal located at a cell boundary of each base station, and a current power level of each of the one or more other base stations A second receiving unit for receiving the first signal; A minimum average transmission rate and a token value information of a terminal located at a cell boundary between the specific terminal and one or more other base stations in the cooperative unit are used to guarantee a minimum average transmission rate of a terminal located at a cell boundary of each base station, A first power level calculator for calculating a first power level vector of the first power level; And And a second power level calculator for calculating a second power level vector that is an updated power level of each base station in the cooperating unit in consideration of the current power level and the first power level of each base station. 14. The method of claim 13, Further comprising: a transmission unit that transmits information including the average transmission rate of the specific terminal, the token value, and the current power level of the specific base station to another base station in the cooperating unit. 14. The method of claim 13, The first power level calculator calculates the first power level vector

Is calculated using the metric of Equation (A), and ensures minimum average data rate and proportional fairness among cells located at cell boundaries of each base station. [Mathematical formula A]

here

Is the average transmission rate of the k < th > terminal of the base station b,

Is an average channel value between the k < th > terminals of the base station b and the base station b,

A set of terminals served by the base station b,

Is a set of cell edge terminals, a is a token weight function,

Is the token value of the k < th > terminal of the base station b,

Is the maximum transmission power of the base station,

Is the average power of noise, and R _min is the minimum average transmission rate. 15. The method of claim 14, The second power level calculator calculates the second power level vector

Is calculated using the following equation (B): Base station apparatus: [Mathematical expression B]

here

Is the current base station power level vector,

Represents the power control constant. 17. The method of claim 16, Wherein the token value is updated using: < EMI ID = [Mathematical expression C]

here

Is the instantaneous transmission rate at time t

R _min is the minimum average transmission rate,

Represents an average channel value between the k < th > terminals of the base station b and the base station b. 14. The method of claim 13, The second power level calculator calculates a second power level of the terminal located at the cell boundary of each base station using the minimum average transmission rate and the token value information of the terminals located at cell boundaries of the remaining base stations excluding the base station having the smallest token value among the base stations in the cooperative unit And calculates a power level of each base station in the cooperating unit ensuring a minimum average transmission rate. 16. The method of claim 15, Wherein the first power level calculator calculates the first power level vector for a specific subchannel using the equation A further including an unused power not used in a previous subchannel of the specific subchannel, Base station apparatus. 17. The method of claim 16, The second power level calculator calculates the second power level vector for a particular subchannel using Equation D: [Mathematical expression D]

Where s is the subchannel index,

Is the power control constant, and t is the time.

Images