KR20110083213A - Transmission Power Control Method of Mobile Terminal Considering Interference Effect of Neighboring Base Stations - Google Patents

Abstract

The present invention relates to a method of controlling the transmission power of a mobile terminal in mobile communication. More particularly, the present invention relates to a method of controlling the transmission power of a mobile terminal, while providing an optimal data transmission rate of the mobile terminal and minimizing the influence of interference on neighboring base stations. It is about.
In the method of controlling the transmission power of a mobile terminal according to the present invention, the target transmission power of the mobile terminal is controlled in consideration of the interference effect of the transmission signal of the mobile terminal on the neighboring base station, thereby minimizing the interference of the transmission signal of the mobile terminal on the neighboring base station. can do. In addition, the method of controlling the transmission power of the mobile terminal according to the present invention controls the target transmission power of each mobile terminal based on the utility function of the mobile terminal, whereby the mobile terminal minimizes the interference to the base station or the neighboring base station and at the same time the maximum transmission of the mobile terminal. Data can be sent at a rate.

Description

Method for controlling transmission power of mobile terminal considering inter cell interference in wireless communication}

The present invention relates to a method of controlling the transmission power of a mobile terminal in mobile communication. More particularly, the present invention relates to a method of controlling the transmission power of a mobile terminal, while providing an optimal data transmission rate of the mobile terminal and minimizing the influence of interference on neighboring base stations. It is about.

Power control used in the mobile communication is to control the power of the signal received from each mobile terminal to the base station in one base station so as to be the same regardless of the distance between the base station and the mobile terminal.

Referring to an example of a method of controlling the transmission power of a conventional mobile terminal with reference to Figure 1, the mobile terminal located in the cell (C) area of the base station and the base station signal (S) to the base station for the mobile terminal to perform communication Send. A plurality of mobile terminals located in the cell (C) area each attempt to transmit data to the base station at the maximum transmission power in order to improve its communication quality. When a plurality of mobile terminals transmit data at their maximum transmission power, respectively. It interferes with other mobile terminals located in the cell C area, thereby degrading the transmission quality of neighboring mobile terminals. Therefore, the base station controls the transmission power of the neighboring mobile terminals to the minimum possible while maintaining good call quality of the mobile terminals located in the cell (C) area. That is, the base station periodically measures the signal-to-interference plus noise ratio (SINR) of the signal received from each mobile terminal in order to control the transmission power of the mobile terminal, and based on the measured signal-to-noise ratio When the signal-to-noise ratio of the received signal is less than the reference signal-to-noise ratio, when the transmission power of the mobile terminal is increased and the signal-to-noise ratio of the received signal is greater than the reference signal-to-noise ratio, power control information for reducing the transmission power of the mobile terminal is transmitted to the mobile terminal.

On the other hand, referring to Figure 2 showing the interference effect of the transmission signal of the mobile terminal to the adjacent base station adjacent to the base station, the signal (S) transmitted by the mobile terminal located in the cell area (A) of the base station is Not only the cell area A but also the cell areas B and C of the base stations located adjacent to the base station are transmitted. Therefore, the signal S transmitted by the mobile terminal acts as an interference to the mobile terminal located in the cell areas B and C of the neighboring base stations, thereby reducing the transmission quality of the mobile terminal located in the cell areas B and C of the neighboring base stations. Results in deterioration. Therefore, by controlling the transmission power of the mobile terminal to the minimum possible so that the transmission signal of the mobile terminal does not interfere with the mobile terminal located in the cell area (B, C) of the neighboring base station while maintaining the good call quality of the mobile terminal, The capacity of the base station can be increased.

However, the above-described power control method of the mobile terminal receives and measures the signal-to-interference noise ratio of the mobile terminal located in the cell area A managed by the base station, and measures the signal-to-interference noise ratio of the mobile terminal based on the measured mobile terminal. Control the transmit power. However, the signal transmitted by the actual mobile terminal at the controlled transmission power is located not only in the cell area A of the base station to which the mobile terminal belongs, but also in the cell areas B and C of the adjacent base station located adjacent to the base station to which the mobile terminal belongs. It also causes interference effects on mobile terminals.

Therefore, although the transmission power of the mobile terminal should be determined in consideration of not only the neighboring mobile terminals of the base station to which the mobile terminal belongs, but also the neighboring base stations affected by the interference of the transmission signal of the mobile terminal, the base station has a signal-to-noise ratio of the mobile terminal belonging to the mobile terminal. There is a problem of controlling the transmission power of the mobile terminal based only on.

Furthermore, the conventional power control method of the mobile terminal simply compares the signal-to-interference noise ratio received from the mobile terminal with the reference signal-to-interference noise ratio and controls the mobile terminal to reduce or increase the transmission power. There is a problem in that control is not possible with the transmission power capable of transmitting data.

It is an object of the present invention to provide a method for controlling a target transmission power of a mobile terminal in consideration of the interference effect of the transmission signal of the mobile terminal on an adjacent base station.

Another object of the present invention is to provide a method of controlling a target transmission power of a mobile terminal so that each mobile terminal can transmit data at the maximum transmission rate while considering the interference effect on neighboring base stations based on the utility function of the mobile terminal. To provide.

In order to achieve the object of the present invention, a method for controlling a target transmission power of a mobile terminal according to the present invention comprises the steps of determining the transmission power and the signal-to-interference noise ratio (SINR) of the mobile terminal in the base station of the cell to which the mobile terminal belongs; Determining a product of a channel gain and a path loss between a mobile station and a neighbor base station in a neighboring base station, and using a product of the transmission power and signal-to-noise ratio of the mobile terminal, and the channel gain and path loss between the mobile terminal and the neighbor base station. Determining the transmission power of the mobile terminal to maximize the utility function considering the interference effect between the mobile terminal and the neighboring base station; determining the determined transmission power of the mobile terminal as the target transmission power of the mobile terminal; Controlling the transmit power of the mobile terminal to a target transmit power of Include.

Here, the utility function is determined by subtracting the sum of interference effects that the mobile station has on the neighboring base station from the maximum data rate that the mobile station can have. Preferably, the utility function is represented by the following equation.

는 이동 단말기와 j번째 인접 기지국 사이의 경로 손실을 의미하며,

는 이동 단말기와 j번째 인접 기지국 사이의 채널 이득을 의미하며,

는 이동 단말기와 기지국 사이의 신호대간섭잡음비를 의미하며, N은 이동 단말기가 간섭을 미치는 인접 기지국(j)의 수인 것을 특징으로 한다.P _i means the transmit power level of the mobile terminal,

Denotes a path loss between the mobile terminal and the jth neighbor base station,

Denotes a channel gain between the mobile terminal and the jth neighbor base station,

Is the signal-to-interference noise ratio between the mobile terminal and the base station, and N is the number of neighboring base stations j interfering with the mobile terminal.

An example of determining a product of a channel gain and a path loss between a mobile terminal and a neighbor base station in a base station located adjacent to a base station includes determining a channel gain and a path loss between the mobile terminal and a neighbor base station at a neighbor base station, and the base station. Receiving information on the channel gain and the path loss determined from the neighboring base station, and using the information on the channel gain and the path loss received from the base station to determine the product of the channel gain and the path loss between the mobile terminal and the neighboring base station The steps are carried out. The information on the channel gain and the path loss calculated here is characterized in that it is received by the base station via a wired / wireless network (backbone network) between the base station and the adjacent base station.

Another example for determining a product of a channel gain and a path loss between a mobile terminal and a neighbor base station in a base station located adjacent to a base station is based on a signal transmitted and received between the mobile terminal and a neighbor base station and reception of the base station. Receiving information on power from the mobile terminal, and determining the product of the channel gain and the path loss between the mobile terminal and the neighboring base station by using the received transmission information of the mobile terminal and the received power information of the base station Is performed.

The transmission power control method of the mobile terminal according to the present invention has the following various effects as compared to the transmission power control method of the conventional mobile terminal.

First, the transmission power control method of the mobile terminal according to the present invention controls the target transmission power of the mobile terminal in consideration of the interference effect of the transmission signal of the mobile terminal to the neighboring base station, the interference of the transmission signal of the mobile terminal to the neighboring base station Can be minimized.

Second, the method of controlling the transmission power of the mobile terminal according to the present invention controls the target transmission power of each mobile terminal based on the utility function of the mobile terminal, whereby the mobile terminal minimizes interference to the base station or the neighboring base station and at the same time maximizes the mobile terminal. Data can be transmitted at the transmission rate.

3 is a view for explaining the effect of interference on the neighboring base station signal transmitted from the mobile terminal to the control base station.

Hereinafter, a base station communicating with a mobile terminal and controlling communication of the mobile terminal is referred to as a control base station, and a base station located adjacent to the base station is referred to as a neighbor base station.

3 is a view for explaining the effect of interference on the neighboring base station signal transmitted from the mobile terminal to the control base station.

Referring to FIG. 3, the mobile terminal i located in the cell region A of the control base station transmits a signal s to the control base station at a controlled transmit power according to a power control command of the control base station. The transmission signal s of the mobile terminal i is transmitted not only to the control base station but also to the adjacent base station of the control base station. Therefore, the transmission power of the mobile terminal i needs to maximize the transmission rate of the mobile terminal and to minimize the influence of interference on the neighboring terminal. A function that maximizes the data rate of the mobile terminal i and at the same time an interference effect on a neighboring terminal is referred to as a utility function. The utility function of the mobile terminal i can be expressed as Equation (1) below. have. In other words, the utility function of the mobile terminal i is expressed as the maximum transmission rate that the mobile terminal i can subtract from the sum of the interference effect of the mobile terminal on the neighboring base station.

[Equation 1]

는 이동 단말기(i)와 j번째 인접 기지국 사이의 경로 손실을 의미하며,

는 상기 이동 단말기와 j번째 인접 기지국 사이의 채널 이득을 의미하며,

는 이동 단말기(i)과 제어 기지국 사이의 신호대수신잡음비를 의미하며, N은 이동 단말기(i)가 간섭을 미치는 인접 기지국(j)의 수를 의미한다.Here, P _i means the transmission power level of the mobile terminal (i),

Denotes a path loss between the mobile terminal i and the jth neighbor base station,

Denotes a channel gain between the mobile terminal and the jth neighbor base station,

Denotes the signal-to-receive noise ratio between the mobile terminal i and the control base station, and N denotes the number of adjacent base stations j interfering with the mobile terminal i.

Here, the path loss between the mobile terminal i and the neighboring base station j may refer to a total loss including shadowing, antenna gain, cable loss, as well as path loss in a small sense.

In FIG. 3, in the control base station controlling transmission power of the mobile terminal, the control base station maximizes the data transmission rate of the mobile terminal and simultaneously considers the effects of the interference of the mobile terminal i on the control base stations 1 and 2. The transmission power of the mobile terminal i is controlled based on equation (1).

4 is a flowchart illustrating a method of controlling transmit power of a mobile terminal according to an embodiment of the present invention.

)는 아래의 수학식(2)와 같이 계산된다.Referring to FIGS. 3 and 4, in order to control the transmission power of the mobile terminal i located in the cell region A of the control base station, the control base station first receives information on the transmission power from the mobile terminal i. The signal-to-interference noise ratio of the signal received from the mobile terminal i is calculated (S1). Signal to interference noise ratio of the signal received from the mobile terminal (i)

) Is calculated as in Equation (2) below.

[Equation 2]

은 열잡음 전력을 의미한다.Where m is the number of mobile terminals located in the vicinity of the control base station 0 and affecting the control base station 0,

Means thermal noise power.

The control terminal 0 determines the channel gain and path loss between the mobile terminal i and the neighboring base stations 1 and 2 in order to measure the interference effect of the mobile terminal i on the neighboring base stations 1 and 2. (S3). The control base station 0 is characterized by the transmission power of the mobile terminal i, the signal-to-noise interference ratio between the mobile terminal i and the control base station 0, and the channel gains of the adjacent terminals 1 and 2 and the mobile terminal 0. The transmission power of the mobile terminal, which maximizes the utility function of the mobile terminal i, is calculated based on the excess path loss (S5). The maximum utility function value of the mobile terminal i is calculated by the following equation (3) and equation (4).

&Quot; (3) "

이고,

이다.here

ego,

to be.

Pi value which maximizes the utility function by partial derivative of Equation (3) with respect to Pi can be calculated as Equation (4) below.

&Quot; (4) "

The control base station 0 determines the maximum transmit power of the utility function of the mobile terminal i as the target transmit power of the mobile terminal i (S7), and the information on the determined target transmit power of the mobile terminal i is determined. Is transmitted to the mobile terminal i to control the transmission power of the mobile terminal i (S9). The mobile terminal i transmits a signal to be transmitted by the mobile terminal i at the target transmission power using the information on the target transmission power received from the control base station 0, whereby the data transmission rate of the mobile terminal i is transmitted. At the same time, the interference effect on the neighboring base station can be minimized.

5 is a schematic diagram of a mobile communication system for explaining an example of a method of determining a product of a channel gain and a path loss between a mobile terminal and a neighbor base station.

Referring to FIG. 5, the signal transmitted by the mobile terminal i is transmitted to the neighbor base stations 1, 2, and 3, and the neighbor base station 1 receives the signal S1 from the mobile terminal i. The neighbor base station 1 calculates a channel gain and a path loss between the neighbor base station 1 and the mobile terminal i based on the received signal S1. Preferably, the path loss is calculated based on the strength reduction of the received signal S1 of the neighboring base station 1, and the channel gain is calculated based on the degree of distortion of the received signal S1. Similarly, the neighbor base station 2 calculates the channel gain and the path loss between the neighbor base station 2 and the mobile terminal i based on the received signal S2, and the neighbor base station 3 receives the received signal. Based on S3, the channel gain and the path loss between the neighbor base station 3 and the mobile terminal i are calculated.

The neighbor base stations 1, 2, 3 transmit the channel gain and path loss between the calculated neighbor base stations 1, 2, 3 and the mobile terminal i to the control base station 0, respectively, and control base station 0 Is a channel gain and path gain between the mobile terminal i and the neighbor base stations 1, 2, 3 based on the received channel gain and path loss between the neighbor base stations 1, 2, 3 and the mobile terminal i. Determine the product of. The control base station 0 calculates the β value by summing the product of the channel gain and the path gain between the mobile terminal i and the neighboring base stations 1, 2, 3.

Here, the control base station 0 and the neighboring base stations 1, 2, and 3 are connected to each other by a wired or wireless backbone network, and each of the neighboring base stations 1, 2, and 3 is calculated by the neighboring base station and the mobile terminal. The channel gain and path loss values between are transmitted to the control base station 0 via the backbone network.

6 is a schematic diagram of a mobile communication system for explaining another example of a method of determining a product of a channel gain and a path loss between a mobile terminal and an adjacent base station.

The mobile terminal i transmits and receives signals for handoff with the neighbor base stations 1 and 2 as well as the control base station 0 where the mobile terminal i is located during movement. That is, the control base station 0 and the neighbor base stations 1 and 2 periodically transmit their own pilot signals to the mobile terminal i, and the mobile terminal receives from the control base station 0 and the neighbor base stations 1 and 2, respectively. A handoff message for selecting a base station for handing off based on one pilot signal is transmitted to the control base station 0 and the neighboring base stations 1 and 2.

The mobile terminal i uses the signals transmitted and received between the mobile terminal i and the neighboring base stations 1 and 2 in the handoff process, so that the mobile terminal i receives the signals transmitted from the mobile terminal i to the neighboring base stations 1 and 2. The product of the channel gain and the path loss between the mobile terminal i and the neighboring terminals 1 and 2 is calculated and calculated from the strength and the strength of the received signal of the neighboring base stations 1 and 2 as shown in Equation (5) below. Information about the product of the channel gain and the path loss between the mobile terminal i and the adjacent terminals 1 and 2 is transmitted to the control terminal 0.

[Equation 5]

The control base station 0 calculates the β value by summing the product of the channel gain and the path loss between the received neighbor base stations 1 and 2 and the mobile terminal i.

Preferably, the mobile terminal i transmits only the strength of the signal transmitted by the mobile terminal i to the neighbor base stations 1 and 2 and the strength of the received signal of the neighbor base stations 1 and 2 to the control base station 0. The control base station (0) uses the equation (5) to calculate the channel gain and path between the mobile station (i) and the adjacent terminal (1, 2) between the neighbor base stations (1, 2) and the mobile terminal (i). The product of the losses can be calculated.

Considering the interference effects of the mobile terminal i, limited to the adjacent base stations 1 and 2 performing handoff with the mobile terminal i, the channel gain and path of the adjacent base station to the control base station 0 directly through the backbone network. Instead of transmitting the loss information, the mobile terminal i transmits the product information of the channel gain and the path loss to the control base station 0, thereby reducing the load of the control base station for controlling the transmission power of the mobile terminal and providing a separate backbone network. Does not require.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium.

The computer-readable recording medium may be an electronic or magnetic storage medium (eg, ROM, floppy disk, hard disk, etc.), optical reading medium (eg, CD-ROM, DVD, etc.) and carrier wave (eg Storage media, such as through the Internet).

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (10)

In the method for controlling the transmission power of the mobile terminal,
(a) determining, at a base station of a cell to which the mobile terminal belongs, a transmission power and a signal-to-reception noise ratio (SINR) of the mobile terminal;
(b) determining a product of a channel gain and a path loss between the mobile terminal and the neighbor base station at a base station located adjacent to the base station;
(c) the mobile terminal maximizing the utility function considering the interference effect of the mobile terminal and the neighboring base station by using the product of the transmission power and the signal-to-receive noise ratio of the mobile terminal, the channel gain and the path loss between the mobile terminal and the neighboring base station; Determining a transmit power of the terminal;
(d) determining the determined transmit power of the mobile terminal as a target transmit power of the mobile terminal; And
(e) controlling the transmission power of the mobile terminal with the determined target transmission power of the mobile terminal. The method of claim 1, wherein the utility function
The transmission power control method of the mobile terminal, characterized in that the maximum transmission rate that the mobile terminal can be determined by subtracting the sum of the interference effect on the neighboring base station. The method of claim 2, wherein the utility function is represented by Equation (1)
[Equation 1]

Here, P _i means the transmission power level of the mobile terminal,

Denotes a path loss (total loss) between the mobile terminal and the jth neighbor base station,

Denotes a channel gain between the mobile terminal and the jth neighbor base station,

Is the signal-to-receive noise ratio between the mobile terminal and the base station, and N is the number of adjacent base stations (j) that the mobile terminal interferes with. The method of claim 3, wherein step (b)
Receiving information about channel gain and path loss between the mobile station and the neighbor base station, determined by the neighbor base station, from the neighbor base station; And
And determining, by the base station, a product of a channel gain and a path loss between the mobile terminal and the neighboring base station by using the received channel gain and path loss information. . 5. The method of claim 4, wherein the calculated channel gain and path loss information is received by the base station through a wired / wireless network between the base station and the adjacent base station. The method of claim 3, wherein step (b)
Determining, by the mobile terminal, transmission power of the mobile terminal and reception power of the base station based on a signal transmitted and received between the mobile terminal and the neighbor base station;
Determining a product of a channel gain and a loss path between the mobile terminal and the neighbor base station based on the determined transmission power and reception power; And
And transmitting the product of the determined channel gain and loss path to the base station. The method of claim 3, wherein step (b)
Receiving information about the transmission power of the mobile terminal and the reception power of the base station from the mobile terminal based on a signal transmitted and received between the mobile terminal and the neighbor base station; And
And determining a product of a channel gain and a path loss between the mobile terminal and the neighboring base station by using the received transmission power of the mobile terminal and the received power information of the base station. Power control method. The method of claim 6 or 7, wherein the product of the channel gain and the path loss between the mobile terminal and the neighbor base station is calculated by the following equation (2),
[Equation 2]

here

Is the transmit power of the mobile terminal,

The transmission power control method of the mobile terminal, characterized in that it means the reception power of the adjacent base station. The method according to claim 6 or 7,
The signal transmitted and received between the mobile terminal and the adjacent base station is
And a signal transmitted / received between the mobile terminal and the neighbor base station for handoff of the mobile terminal. 10. The method of claim 9, wherein the neighbor base station
And a base station adjacent to the base station capable of receiving a signal for handoff with the mobile terminal.

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