JP4675403B2 - Base station transmission power control method and apparatus - Google Patents

Description

  The present invention relates to a cellular communication system that forms a service area by combining a plurality of radio zones (cells) formed by a plurality of base stations.

In the cellular communication system, the frequency used by each cell is reused between cells, and signals having the same frequency from other cells become interference.
FIG. 4 is a diagram for explaining a situation of interference from other cells in the downlink.
In this figure, BS is a base station and MS is a terminal. Here, it is assumed that adjacent cells use the same frequency (one-cell frequency repetition). As illustrated, the terminal MS _i belonging to the base station BS _i, so that the interference signal from the base station BS of another cell, such as a base station BS _k with the desired signal from the base station BS _i is received.

周辺からの干渉が大きくなればなるほど式（１）の分母が大きくなるため、ＳＩＮＲが低くなり、伝送品質が悪くなってしまう。
このように、セルラ通信システムでは、端末が基地局と通信を行う際、周辺基地局で送信される同一周波数の電波が干渉となり、端末において十分な伝送品質を得ることができず、システム容量（スループットやユーザの同時接続数）が制限されてしまうという問題がある。 SINR (signal to interference noise ratio) is used as an index representing transmission quality. If the SINR is high, the transmission quality is good, and if the SINR is low, it is bad.
SINR is expressed by the following equation.

The greater the interference from the periphery, the larger the denominator of equation (1), so the SINR is lowered and the transmission quality is degraded.
Thus, in a cellular communication system, when a terminal communicates with a base station, radio waves of the same frequency transmitted from neighboring base stations interfere with each other, and sufficient transmission quality cannot be obtained at the terminal. There is a problem that the throughput and the number of simultaneous connections of users) are limited.

In addition, there are the following two methods as conventional base station power adjustment methods.
One is a method in which the same power is set and transmitted to all base stations, and the other is a base so that a required SNR (signal to noise power ratio) is achieved for terminals in each base station. This is a method of performing power control for each station.
However, neither method considers the interference power from the neighboring base stations. Therefore, there is a possibility that SINR deteriorates due to the interference and the required transmission quality cannot be satisfied.
In addition, by controlling the transmission power of the common control channel using information on the status of the service area and the total transmission power, pilot channel transmission power, and uplink interference amount in the neighboring base stations, it is shared in cooperation with the neighboring base stations. A transmission power control method that can autonomously set the transmission power of the control channel and perform cell formation has also been proposed (Patent Document 1).
JP 2006-135673 A

As described above, in cellular mobile communication, the same frequency interference from neighboring cells is a factor that limits the overall system capacity.
In order to avoid this, it is necessary to calculate the interference that each base station gives to the terminals of the neighboring base stations in advance, and to coordinate the power control of the base stations so that each terminal can obtain the required transmission quality. .
Consider a method for determining the transmission power of a plurality of base stations so that the received SINR at the terminal can satisfy the required transmission quality.

Assume 1-cell repetition at a frequency as shown in FIG. In each cell, only one terminal using the frequency can exist as a terminal capable of communication.
Terminal transmission power of the base station BS _i p _i, the transmission power p _k of the base station BS _k, the propagation loss from the base station BS _i to the terminal MS _i belonging to the base station BS _i z _ii, from the base station BS _k If the propagation loss up to MS _i is z _ik , the desired signal power is p _i z _ii and the interference signal power from the base station BS _k is p _k z _ik .
Assuming that the number of base stations is N (N is an integer of 2 or more) and the noise power at the terminal MS _i is n _i , the received SINR _{i at the} terminal MS _i satisfies the required transmission quality γ _{req, i} in the following manner. It is necessary to satisfy the conditions.

ただし、立式にあたっては、各端末での各基地局からの伝播損及び雑音レベルの推定が必要である。 For all terminals that exist in all base stations, create a conditional expression that converts the inequality sign in equation (2) above to an equal sign, that is, the transmission quality of each terminal is equal to the required transmission quality. Then, simultaneous equations with the power of each base station as a variable are obtained.

However, in the standing ceremony, it is necessary to estimate the propagation loss and noise level from each base station at each terminal.

By solving the simultaneous equations of Equation (3), it is possible to obtain the transmission power of each base station when the transmission quality at all terminals becomes the required transmission quality γ _{req, i} .
However, the transmission power p _i (i = 1 to N) of each base station needs to satisfy 0 ≦ p _i ≦ P _limit where the maximum transmission power of the base station is P _limit (constraint conditions for base station power) .
However, the power solution may be out of the range that the base station can output. For example, the solution may be a negative value.

If the solution of the simultaneous equations does not satisfy the constraint conditions, it is impossible for all terminals to communicate with the required quality. Therefore, the number of terminals that allow communication is reduced so as to satisfy the constraint conditions. Temporarily cut off the communication of several terminals, that is, cut off the transmission power of the base station to which the terminal belongs, thereby reducing the variables and formulating the simultaneous equations again so that the solution satisfies the constraints. Find the solution. Here, when reducing the number of terminals, an evaluation rule is to increase the number of terminals that can be connected simultaneously as much as possible.
The most effective method is to solve simultaneous equations for all combinations of terminals that allow communication, and to find a combination of terminals that satisfy the base station power constraint condition that maximizes the number of simultaneously connected terminals (total Full search).

FIG. 5 is a flowchart showing the flow of power allocation control processing for determining the transmission power of each base station using the brute force method. Here, it is assumed that the number of base stations is N (N is an integer greater than or equal to 2), and there are a total of N terminals, one for each cell.
When power allocation control is started, first, preprocessing for formulating the simultaneous equations, that is, estimation of the state of the transmission path from each base station to each terminal (propagation loss) and noise power at each terminal, etc. Is performed (step S21).
Then, an initial value 0 is set to a variable i indicating the number of terminals to be reduced (step S22), and all combinations for removing i terminals from N terminals are calculated (step S23).
Then, 1 is set to the variable j indicating the order in the combination to be removed from the N terminals (step S24).
Next, for the j-th combination among the combinations obtained in step S23, the simultaneous equations of the equation (3) are formed and the solution is obtained (step S25). In the initial state, the number of terminals to be removed is 0, and the simultaneous equation of the above-described equation (3) is formed and its solution is obtained.

Then, it is determined whether or not the obtained solution satisfies the base station power restriction condition described above (step S26).
As a result, if the obtained solution satisfies the constraint condition, the solution is determined as the transmission power of each base station, assigned to each base station (step S27), and this power allocation control process is terminated. .
On the other hand, if any of the obtained solutions does not satisfy the constraint condition, it is determined whether or not the combination is the last combination _N C _{i to be} removed from N terminals (step S28). ). As a result, if it is not the last combination, j is set to j + 1 (step S30), the process proceeds to step S25, the simultaneous equations are formulated for the next combination, its solution is obtained, and the above-described processing is repeated.
If the result of determination in step S28 is the last combination, it is determined whether i is equal to N (step S29). If i = N, all terminals are reduced. Therefore, it is determined that transmission power allocation is impossible, and this power allocation control process is terminated.
If i is not equal to N, i is set to i + 1 (the number of terminals to be reduced is increased by 1), and the process proceeds to step S23, and the above-described processing is repeated again from the calculation of the combination to remove i from N terminals. .

In this way, the brute force method can obtain accurate results by sequentially formulating simultaneous equations for all combinations that remove i terminals from N terminals, and obtaining a solution. There is a problem that the amount of calculation increases exponentially as the number of base stations to be performed increases. For example, when the number of base stations performing cooperative control is 100 or more, a huge calculation is required, which is not realistic.
Therefore, an object of the present invention is to provide a base station transmission power control method and apparatus in a cellular communication system that can greatly improve the system capacity with a small amount of calculation.

To achieve the above object, a base station transmission power control method according to the present invention is a base station transmission power control for controlling transmission power of a plurality of base stations in a cellular communication system having a plurality of base stations and a plurality of terminals. A simultaneous equation using the transmission power of the plurality of base stations as a variable so that a signal-to-interference noise ratio at a terminal belonging to each of the plurality of base stations becomes a required value , A first step of finding a solution; a second step of setting the solution as transmission power of the plurality of base stations when the solution of the simultaneous equations satisfies a constraint condition of base station power; If the solution of the equation does not satisfy the constraints of the base station power, before to reduce the terminal belonging to sum the largest base station of the interference signal power to be supplied to the plurality of terminals of the plurality of base stations No. Proceeds to step, and has a third step of Tatsushiki newly the simultaneous equations under the conditions blocked the transmission power of the base station that has been reduced to the terminal.
Also , transmission power control is performed for each base station by determining the total interference signal power that each base station gives to the plurality of terminals on the assumption that all base stations transmit at the maximum power. by each base station assuming things determine the sum of interference signal power to be supplied to said plurality of terminals, or a low signal-to-interference noise ratio than the required value of the signal-to-interference noise ratio the signal to interference plus noise By determining the total interference signal power that each base station gives to the plurality of terminals, using the solution obtained by solving the simultaneous equations as the required value of the ratio as the provisional transmission power of each base station, the terminal The base station to be reduced is determined.

In addition, the base station transmission power control apparatus of the present invention is a base station transmission power control apparatus for controlling the transmission power of the plurality of base stations in a cellular communication system with multiple base stations and multiple terminals, First, a simultaneous equation using the transmission power of the plurality of base stations as a variable is established so that a signal-to-interference noise ratio at a terminal belonging to each of the plurality of base stations becomes a required value , and a first solution for solving the simultaneous equations is obtained. And a second means for setting the solution as the transmission power of the plurality of base stations when a solution of the simultaneous equations satisfies a base station power constraint, and a solution of the simultaneous equations is the If the base station power constraint condition is not satisfied, the number of terminals belonging to the base station having the largest total interference signal power given to the plurality of terminals among the plurality of base stations is reduced, and the first means To said end Those having a third means for executing processing for Tatsushiki newly the simultaneous equations under the conditions blocked the transmission power of the reduced-base station is.

According to the base station transmission power control method and apparatus of the present invention as described above, every time one uniquely determined terminal is removed, the simultaneous equations are solved, and it is determined whether the solution satisfies the base station power constraint condition. However, by repeating the process of selecting the terminal to be removed again if not satisfied, it is possible to significantly reduce the amount of calculation as compared with the brute force method that solves the simultaneous equations for all combinations.
Therefore, the transmission power of each base station can be determined with a small amount of computation so that the base station power constraint condition is satisfied and the number of simultaneously connected terminals can be increased as much as possible.

FIG. 1 is a diagram showing a configuration of a cellular communication system to which a base station transmission power control method of the present invention is applied. In this figure, 1 ₁ to 1 _N are base stations (N is an integer of 2 or more), 2 ₁ to 2 _N are terminals, and 3 is a control station that controls the plurality of base stations. Each base station 1 ₁ to 1 _N forms a cell, and each base station uses the same frequency. Terminals 2 ₁ to 2 _N located in each cell communicate with the base stations 1 ₁ to 1 _N forming the cell. In this figure, it is described that the terminals 2 ₁ to 2 _N exist in all the cells. However, when the terminal 2 does not exist in the cell, a plurality of terminals 2 exist in one cell. May be present. However, since the same frequency is used, only one terminal 2 can communicate with the base station using that frequency within one cell.
Control station 3 is connected to the plurality of base stations 1 ₁ to 1 _N, determines the transmission power of each base station 1 ₁ to 1 _N based such as on information obtained through the respective base stations 1 ₁ to 1 _N Then, the determined transmission power is notified to each of the base stations 1 ₁ to 1 _N. The base stations 1 ₁ to 1 _N control their own transmission power so as to be the transmission power notified from the control station 3. In the present invention, a plurality of base stations perform transmission power control in cooperation in this way.

Hereinafter, the power allocation control process for determining the transmission power of each of the base stations 1 ₁ to 1 _N executed in the control station 3 will be described.
In the present invention, when it is impossible to determine the base station transmission power so that all terminals satisfy the required transmission quality, the number of terminals permitted to communicate is reduced to the remaining base stations. When determining the transmission power, instead of solving the simultaneous equations for all combinations as in the round robin method described above, the terminals to be removed are uniquely selected based on a predetermined criterion, and the simultaneous equations are calculated each time the terminals are removed. If the solution does not satisfy the constraint condition of the base station power, the process of uniquely selecting the terminal to be removed again is repeated. As a result, the amount of calculation is greatly reduced compared to the brute force method described above.

FIG. 2 is a flowchart showing the flow of the power control process of the present invention.
When this power allocation control process is started, first, pre-processing for formulating the simultaneous equations of the above-described expression (3) is performed (step S1). That is, z _ik (1 ≦ k ≦ N) (propagation loss from the base station k to the terminal i belonging to the base station i) and n _i (noise power at the terminal i) in the equation (3) are prepared.
Further, propagation loss z _ik from each base station ₁ 1 to 1 _N to each terminal 2 ₁ to 2 _N, for example, pilot channel signal from each base station ₁ 1 to 1 _N in each terminal 2 ₁ to 2 _N The received power can be estimated. In each of the terminals 2 _{1 to} 2 _N , the received power of the pilot channel signals from the base stations 1 ₁ to 1 _N is measured, and the measured values are assigned to the terminals 2 ₁ to 2 _N via the uplink channel. and notify the base station ₁ 1 to 1 _N and notifies the control station 3 from the base station ₁ 1 to 1 _N. Control station 3, the transmission power p _i of the pilot channel notified each terminal 2 ₁ to 2 received power of a pilot channel signal from the base station 1 ₁ to 1 _N in _N and each base station 1 ₁ to 1 _N Based on this, the propagation loss z _ik from each base station 1 ₁ to 1 _N to each terminal 2 ₁ to 2 _N is estimated.
The noise power n _{i at} each of the terminals 2 _{1 to} 2 _N is, for example, the received power of the pilot channel signal from each of the base stations 1 ₁ to 1 _N from the received power of the pilot channel signal at each of the terminals 2 ₁ to 2 _N. Can be calculated by subtracting. In addition, it can be estimated from the bandwidth. In each of the terminals 2 _{1 to} 2 _N , the noise power n _i may be obtained, and the value may be notified to the base stations 1 ₁ to 1 _N to which the terminals 2 ₁ to 2 _N are connected.

After performing the pre-processing (step S1) for the simultaneous equation formulation in this way, the simultaneous equation of the equation (3) is formulated and its solution is obtained (step S2). _{That, SINR i (1 ≦ i ≦} N) in each terminal 2 ₁ to 2 _N is the required transmission quality gamma _req set in advance to each terminal _{2 1 ~2 N, i (1} ≦ i ≦ N) The transmission power p _i (1 ≦ i ≦ N) of each of the base stations 1 ₁ to 1 _N is calculated.
Then, it is determined whether or not the obtained solution p _i satisfies the constraint condition of base station power, 0 ≦ p _i ≦ P _limit (step S3). Here, P _limit is the maximum transmission power of each of the base stations 1 ₁ to 1 _N.
As a result of this determination, if all of the transmission powers p _i (1 ≦ i ≦ N) of all the base stations 1 ₁ to 1 _N satisfy the constraint condition, the obtained solution p _i is The transmission power of each of the base stations 1 ₁ to 1 _N is allocated (step S4), and this power allocation control process is terminated.

Results of the determination of the step S3, if the solution p _i does not meet the constraint condition exists, determines whether or not the remaining number of terminals is 0 belonging to the base station as a cooperative control target ( Step S5). As a result, when the number of remaining terminals is 0, assignment is impossible, and this assignment control is terminated.
When the number of remaining terminals is not 0, the process proceeds to step S6, and a process of reducing one terminal that permits communication is performed. Although details of this reduction processing will be described later, in the present invention, the terminal to be removed is uniquely selected on the basis of a predetermined criterion, instead of trying all the calculations as in the brute force method (Full search). I am doing so. In this embodiment, the amount of interference (interference signal power) given to all terminals 2 ₁ to 2 _N by each base station 1 ₁ to 1 _N is calculated, and terminals belonging to the base station having the largest sum are removed. Yes. Thus, by uniquely determining the terminal to be removed, the amount of calculation can be greatly reduced as compared with the round robin method that calculates all combinations.
Since the base station to which the reduced terminal belongs has been deleted, the transmission power is set to 0, and the simultaneous equations are established for the remaining base stations.
That is, returning to the step S2, the simultaneous equations of the equation (3) are formed in a state where the number of terminals is reduced, and a new solution p _i is obtained.

Then, the process proceeds to step S3, where it is determined whether or not the solution obtained by the newly formed simultaneous equations satisfies the constraint condition. If the constraint condition is satisfied, the solution p _i is determined by the base station. Allocation as power (step S4), and the power allocation process is terminated.
When the solution of the newly formed simultaneous equations does not satisfy the constraint conditions, the process proceeds to step S5. When the remaining number of terminals is not 0, the process proceeds to step S6 and is removed in the same manner as described above. Process to select the terminal. Then, returning to step S2, the simultaneous equations in a state where the number of terminals is further reduced are formed, and a solution p _i is obtained.
Hereinafter, similarly, the simultaneous equations are solved by removing terminals one by one based on a predetermined criterion until the solution p _i satisfies the constraint condition or the remaining number of terminals becomes zero, The process of determining whether or not the constraint condition is satisfied and selecting the terminal to be removed if not satisfied is repeated.

The process for reducing the number of terminals in step S6 will be further described.
As described above, in step S6, the amount of interference given to each of the terminals 2 ₁ to 2 _N by the base stations 1 ₁ to 1 _N is calculated, and the terminal 2 _i belonging to the base station 1 _i having the largest sum is removed. (Interference maximum base station selection method). That is, since a base station with a large amount of interference with a terminal is a harmful effect for satisfying the constraint condition of the base station power, a terminal belonging to the base station with the largest amount of interference is removed.

この合計値が最も大きな値を示す基地局１_kに属する端末２_kを取り除く端末として選択する。 Here, in order to calculate the amount of interference (interference signal power p _k z _ik ) from the base stations 1 ₁ to 1 _N to the terminals 2 ₁ to 2 _N , the transmission power p _{k of} each base station 1 ₁ to 1 _N is calculated. (1 ≦ k ≦ N) must be determined temporarily. Therefore, any one of the following three types of calculation methods is used. Suppose that the transmission power to be determined is p _k ′.
(1) Maximum power selection Assuming that all base stations 1 ₁ to 1 _N are transmitting at the maximum power P _limit , that is, p _k ′ = P _limit, and for each base station 1 _k (1 ≦ k ≦ N) Then, the total I _k of interference signal power to the terminals 2 _i (1 ≦ i ≦ N, where i ≠ k) other than the terminal 2 _k belonging to the own base station is calculated as shown in Equation (4).

The terminal 2 _k belonging to the base station 1 _k showing the largest total value is selected as a terminal to be removed.

(2) Selection of power control for each base station After performing power control for each base station, the interference signal power to all terminals 2 ₁ to 2 _N other than the terminal 2 _k belonging to its own base station of the base station 1 _k Calculate the total. The terminal 2 _k belonging to the base station 1 _k having the largest total value is selected as the terminal to be deleted. That is, in the terminal 2 _k belonging to the base station 1 _k, SNR of the signal from the base station 1 _k is x [dB] to become as its transmission power p _k as to control the transmission power of the base station 1 _k ' Using the determined transmission power, the total interference signal power given to all the terminals 2 ₁ to 2 _N other than the terminal 2 _{k is obtained} as shown in Expression (4). The terminal 2 _k belonging to the base station 1 _k having the largest total value is selected as the terminal to be deleted.

(3) Low required power cooperative selection In the equation (3), the required transmission quality γ _{req, i} is lower than a set value so as to obtain a solution that can satisfy the constraint condition of the base station power. As a value, a simultaneous equation is formed. Based on the transmission power p _k ′ (1 ≦ k ≦ N) of the base stations 1 ₁ to 1 _N satisfying the constraint condition derived by the simultaneous equations, the interference signal power to all the terminals 2 ₁ to 2 _N And the terminal 2 _k belonging to the base station 1 _k having the largest total value is selected as a terminal to be deleted.

  Thus, in the present invention, when the base station transmission power calculated by the simultaneous equations of the above equation (3) does not satisfy the base station power constraint condition, the interference signal power to be given to the terminals belonging to other base stations The terminal belonging to the base station with the largest is removed from the communication target, the transmission power of the base station is set to 0, the simultaneous equations are formed again for the remaining base stations, and the new simultaneous equations are solved. Therefore, the transmission power of each base station is determined so that the number of terminals to be removed is minimized, that is, the number of terminals to be simultaneously connected can be increased as much as possible while satisfying the constraint conditions with a small amount of calculation. Can do.

FIG. 3 is a diagram illustrating a result of evaluating a user simultaneous connection rate, which is a probability that the terminal can satisfy the required reception SINR, using a computer simulation. The vertical axis represents the user simultaneous connection rate, and the horizontal axis represents It shows the required transmission quality of the terminal. Assume an environment in which the number of cells is 19 and one user exists in each cell. The propagation loss is assumed to be inversely proportional to the 3.5th power of the distance, and the cell radius, the maximum transmission power of the base station, and the noise power are set so that the maximum received SNR at the cell edge is 10 dB. It is assumed that the propagation loss and noise power are ideally obtained, and the required received SINR (γ _{req, i} ) for all users is equal.
In the figure, a is a brute force method (Full search), b is (1) maximum power selection, c is (2) power control selection per base station, d is (3) low required power cooperative selection, and e and f are plural. This is a conventional technique that does not perform base station coordination, and e is a method for performing power control for each base station (for each base station, the power is determined so that the SNR at the terminal is γ _{req, i} + x [dB]), f Indicates each case of a method of outputting at the maximum transmission power in all base stations.
As shown in this figure, by performing base station cooperative control, the user simultaneous connection rate can be greatly improved as compared with the cases of e and f in which base station cooperative control is not performed.
In addition, in the case of (2) per-base station power control selection of c and (3) low required power cooperative selection of d, the amount of calculation is small, but the case of a round-robin method of a It can be seen that the performance of 90% or more is maintained.

In the above, when the solution obtained by the simultaneous equations does not satisfy the base station power constraint condition, when the terminal to be removed is uniquely selected, the terminal belonging to the base station having the largest amount of interference given to the terminal Are sequentially removed, but a terminal to be removed may be selected based on other criteria.
In the above description, the control station 3 performs the power allocation control process. However, any one of the plurality of base stations may have the function of the control station 3.

It is a figure which shows the structure of the cellular communication system to which the base station transmission power control method of this invention is applied. It is a flowchart which shows the flow of a power allocation control process. It is a figure which shows the result of having evaluated the user simultaneous connection rate which is a probability that a terminal can satisfy | fill required reception SINR using computer simulation. It is a figure for demonstrating the mode of the interference from the other cell in a downlink. It is a flowchart which shows the flow of the process of a brute force method.

Explanation of symbols

1 ₁ to 1 _N : base station, 2 ₁ to 2 _N : terminal, 3: control station

Claims (5)

A base station transmission power control method for controlling transmission power of the plurality of base stations in a cellular communication system having a plurality of base stations and a plurality of terminals,
First, a simultaneous equation using the transmission power of the plurality of base stations as a variable is established so that a signal-to-interference noise ratio at a terminal belonging to each of the plurality of base stations becomes a required value , and a first solution for solving the simultaneous equations is obtained. And the process of
A second step of setting the solution as the transmission power of the plurality of base stations when the solution of the simultaneous equations satisfies the constraint condition of the base station power;
When the solution of the simultaneous equations does not satisfy the constraint condition of the base station power, the number of terminals belonging to the base station having the largest total interference signal power given to the plurality of terminals among the plurality of base stations is reduced. It goes before Symbol first step Te, the base station; and a third step of Tatsushiki newly the simultaneous equations under the conditions blocked the transmission power of the base station that has been reduced to the terminal Transmission power control method. Assuming that all base stations are transmitting with the maximum power, each base station determines the base station from which the terminal is reduced by determining the total interference signal power given to the plurality of terminals. The base station transmission power control method according to claim 1, wherein: Assuming that transmission power control is performed for each base station, the base station to which the terminal is reduced is determined by obtaining the total interference signal power that each base station gives to the plurality of terminals. The base station transmission power control method according to claim 1 . The solution obtained by solving the simultaneous equations lower SINR than the required value of the signal-to-interference noise ratio as the required value of the signal-to-interference noise ratio as the transmission power of the temporary each base station, by each base station obtains the total of the interference signal power to be supplied to said plurality of terminals, the base station transmission power control method according to claim 1, wherein determining the base station which the terminal is reduced. A base station transmission power control apparatus for controlling transmission power of the plurality of base stations in a cellular communication system having a plurality of base stations and a plurality of terminals,
First, a simultaneous equation using the transmission power of the plurality of base stations as a variable is established so that a signal-to-interference noise ratio at a terminal belonging to each of the plurality of base stations becomes a required value , and a first solution for solving the simultaneous equations is obtained. Means of
A second means for setting the solution as the transmission power of the plurality of base stations when the solution of the simultaneous equations satisfies a constraint condition of the base station power;
When the solution of the simultaneous equations does not satisfy the constraint condition of the base station power, the number of terminals belonging to the base station having the largest total interference signal power given to the plurality of terminals among the plurality of base stations is reduced. And a third means for causing the first means to execute a process for newly formulating the simultaneous equations under the condition that the transmission power of the base station whose number of terminals has been reduced is cut off. Station transmission power control device.

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