KR101023087B1 - Method for controlling transmission power in indoor station - Google Patents

Abstract

The present invention relates to a transmission power adjusting method in an indoor base station, by adjusting the transmission power for a downlink signal through cooperation with an adjacent indoor base station, so that it can be directly applied to the system without additional leveling work. An object of the present invention is to provide a transmission power adjusting method in a base station.

To this end, the present invention, the transmission power control method in the indoor base station, the step of storing the minimum value and the maximum value corresponding to the channel state information; And adjusting the transmission power so that the channel state information from the terminal is between the minimum and maximum values, and if the maximum transmission power is exceeded, requesting the transmission power reduction to the adjacent indoor base station through the communication network. Include.

Portable Internet, Indoor, Outdoor, Power Transmission, Channel Status, Internet

Description

METHOOD FOR CONTROLLING TRANSMISSION POWER IN INDOOR STATION}

The present invention relates to a method for adjusting a transmission power in an indoor base station, and more particularly, by adjusting a transmission power for a downlink signal through cooperation with an adjacent indoor base station, it can be directly applied to a system without additional leveling work. The present invention relates to a transmission power adjusting method in an indoor base station.

In the following embodiment, an indoor mobile Internet base station is described as an example of an indoor base station, but it is apparent that the present invention is not limited thereto.

There are two signals that need to adjust the transmission power. The first is to adjust the transmission power of the signal transmitted from the base station to the terminal, that is, the downlink signal, and the second is the signal transmitted from the terminal to the base station, that is, uplink. The transmission power of the link signal is adjusted.

The transmission power control for the downlink signal at the base station has been applied to the cellular mobile communication system. European GSM systems have downlink transmission power between 5 and 33 dBm and can adjust the transmission power at intervals of 2 dB. In addition, the method proposed by Qualcomm for the IS-95 system can adjust the transmission power in 0.5dB steps over a total of 12dB.

Algorithms for adjusting the transmission power of each base station can be largely divided into a centralized power control method and a distributed power control method.

The central control method collects the situation information of the base station existing in the network from the central node and adjusts the transmission power of each base station based on the information. This central control method has the advantage of determining the optimal transmission power because all the conditions of the network can be considered, but a central node that collects the situation of all base stations to determine the transmission power is also required. The disadvantage is that the computational complexity of the algorithm is high.

The dispersion control method of transmission power is a method in which each base station determines its own transmission power. That is, each base station adjusts its own transmission power to ensure the quality of service to the terminal of the cell based on its local information.

Since the central control method is difficult to apply to an actual system, a dispersion control method is used.

Hereinafter, the dispersion control method will be described in detail.

In order for each base station to adjust the power of the downlink signal, channel state information is required. Terminals present in each cell receive a signal from a base station to grasp channel state information, and feed back the information to the base station. Then, each base station determines the power of the signal it transmits based on the channel state information.

In this case, the channel state information includes a carrier-to-interference noise ratio (CINR), a received signal strength indication (RSSI), a frame error rate (FER), and the like.

Hereinafter, a conventional downlink transmission power adjusting method will be described.

First, in the conventional downlink transmission power control method using a power step, each base station increases the transmission power by a predetermined power step (0.5dB or 2dB) if the channel state is not good, based on the channel state information of its own cell. If the channel environment is good, the transmission power is adjusted by reducing the transmission power by a certain power step.

The conventional method of adjusting by a predetermined power step according to the channel state has a problem that each base station takes a considerable time to reach a stable state through distributed power adjustment.

On the other hand, based on the channel state information received from each base station, algorithms for adjusting the transmission power using the following Equations 1 to 3 have been proposed.

는 i 번째 기지국에서 k 번째 타임 슬롯에 전송하는 전송파워를 나타내고,

은 해당 셀에서 피드백받은 채널 상태정보를 나타내며,

은 해당 기지국이 목표로 하는 채널 상태(환경)를 나타낸다. 그리고

와

는 양의 실수(Real Number)로 조절 가능한 값이다.In [Equation 1] to [Equation 3],

Denotes transmission power transmitted from the i th base station to the k th time slot,

Indicates channel status information fed back from the cell.

Denotes a channel state (environment) that the base station targets. And

Wow

Is an adjustable value with a positive real number.

In the method of adjusting transmission power by using Equations 1 to 3, each base station adjusts transmission power so as to maximize its cell service efficiency using only local information about its cell. do.

Therefore, if the transmission power of the adjacent cell is increased and the interference effect on the cell is increased and the service is not performed smoothly, the base station also increases its transmission power.

That is, since the conventional transmission power adjusting method causes an increase in the overall transmission power for all the base stations around, the normalization of the separate transmission power is required to prevent the transmission power from diverging.

It is a problem of the present invention to solve the problems of the prior art as described above.

Accordingly, the present invention provides a method for adjusting a transmission power in an indoor base station by adjusting a transmission power for a downlink signal through cooperation with an adjacent indoor base station, so that the system can be directly applied to the system without additional leveling. There is a purpose.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a transmission power adjusting method in an indoor base station, the method comprising: storing a minimum value and a maximum value corresponding to channel state information; And adjusting the transmission power so that the channel state information from the terminal is between the minimum and maximum values, and if the maximum transmission power is exceeded, requesting the transmission power reduction to the adjacent indoor base station through the communication network. Include.

The method may further include transmitting a signal by selecting a value closest to the determined transmission power value among the discontinuous power levels after determining the transmission power through the transmission power adjusting method.

On the other hand, the present invention proposes an appropriate adjustment method of the transmission power for the downlink signal transmitted to the terminal by the base station in the cellular mobile communication system. In particular, the present invention proposes a method of controlling downlink transmission power of an indoor base station in a portable Internet system composed of an outdoor / indoor base station.

In addition, the present invention includes the characteristics of the portable Internet system consisting of outdoor / indoor base station, that is, unlike the cellular mobile communication system, because the indoor base station is a small base station that can be installed and moved by the user arbitrarily changes the network environment Considering the possibility of interference and the effect of interference on indoor base stations changing rapidly over time, it is not necessary to adjust the power control scheme used in cellular mobile communication systems, but to use the downlink power control scheme suitable for indoor mobile Internet base stations. present.

In addition, the present invention proposes a power adjustment method that can be applied to both the outdoor base station and the indoor base station using a different frequency and when using the same frequency.

In addition, the present invention provides a method of adjusting the transmission power for the downlink signal of the indoor base station in a portable Internet system consisting of an outdoor / indoor base station.

The present invention also provides an indoor base station downlink transmission power control scheme when the outdoor base station and the indoor base station use different frequencies, and an indoor base station when the outdoor base station and the indoor base station use the same frequency. It suggests a downlink transmission power adjustment method.

In addition, the present invention proposes an adjustment scheme for a continuous transmission power level and an adjustment scheme for a discontinuous transmission power level.

The present invention as described above, by adjusting the transmission power for the downlink signal through cooperation with the adjacent indoor mobile Internet base station, there is an effect that can be applied directly to the system without additional leveling work.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It can be easily carried out. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an embodiment of a portable Internet system including an outdoor / indoor base station to which the present invention is applied.

As shown in FIG. 1, the portable Internet system composed of an outdoor / indoor base station to which the present invention is applied includes an outdoor base station 101 for communicating with a terminal 102 installed outdoors and moving over a wide area, and An indoor base station 103 for communicating with a terminal 104 which is installed in an indoor environment such as a home or a business and is present indoors.

When the terminal, which was provided with the service through the outdoor base station in the outdoors, moves indoors, the terminal performs handover to the indoor base station and receives the service through the indoor base station. Similarly, when the terminal moves from indoors to outdoors, it can be provided without interruption through handover.

In such a portable Internet system composed of outdoor / indoor base stations, if the outdoor base station and indoor base station use the same frequency, they interfere with each other, and when the outdoor base station and indoor base station use different frequencies, indoors Interference is only affected between cells.

2 illustrates an example of cell coverage between indoor base stations in a portable Internet system to which the present invention is applied, and illustrates cell coverage by installation and transmission power of an indoor base station.

In general, since the size of the indoor environment, such as home, depends on the size of the building, the required coverage also varies in size for each cell. However, when all indoor base stations transmit signals with the maximum transmission power, the coverage of adjacent cells overlaps as shown in FIG. 2 (a), and greatly affects the interference between cells, thereby providing a normal service. Can't.

On the other hand, as shown in (b) of FIG. 2, when the indoor base station adjusts the appropriate transmission power, each cell can reduce the interference to the adjacent cell through the appropriate transmission power to enable optimal service.

Hereinafter, when the outdoor base station and the indoor base station use different frequencies, a method of adjusting the downlink transmission power of the indoor base station to the continuous power level will be described. In this case, the influence of the outdoor base station can be ignored, so only interference between indoor base stations is considered.

3 is an exemplary diagram of an indoor base station network of a portable internet system to which the present invention is applied, and illustrates a situation in which indoor base stations are installed and operated in a home.

The user can install the indoor base station anywhere in the home. The installed home base station is connected to the Internet.

Therefore, when the home base station is powered on, first, by using the frequency scanning to determine the information of the outdoor base station and indoor base station in the surroundings, and collects information on the basic network situation.

Information exchange between base stations is also possible through the Internet. When the correct installation is completed, the service is performed to the terminal existing indoors. When the base station transmits data in downlink, the terminal periodically feeds back information about the radio channel environment, that is, channel state information to the base station.

Then, the base station performs downlink transmission power adjustment based on the channel state information transmitted from the terminal. In this case, the channel state information includes Carrier-to-Interference and Noise Ratio (CINR), Received Signal Strength Indication (RSSI), and the like.

4 is a flowchart illustrating a method for adjusting a transmission power in an indoor portable Internet base station according to the present invention.

First, the indoor portable Internet base station stores the minimum and maximum values corresponding to the channel state information (401).

Then, the transmission power is adjusted so that the channel state information from the portable Internet terminal is located between the minimum value and the maximum value. If the maximum transmission power is exceeded, the transmission power is transmitted to the adjacent indoor portable Internet base station through a communication network (eg, the Internet). Request a reduction of 402.

That is, when the CINR value from the portable Internet terminal does not exceed the minimum value, the transmission power is increased to exceed the minimum value through Equation 4 below. At this time, even if the transmission power is increased to the maximum, if the CINR value from the portable Internet terminal does not exceed the minimum value, the transmission power is requested to the adjacent indoor portable Internet base station via the Internet.

Through this process, it is possible to solve the problem that each indoor portable Internet base station competitively increases the transmission power by adjusting the transmission power in cooperation with neighboring indoor portable Internet base stations.

Hereinafter, a transmission power adjusting method in an indoor portable Internet base station according to the present invention will be described in more detail with reference to Equation 4 below.

First, each indoor base station stores the maximum transmission power (Ptx_max) that can be transmitted in consideration of the influence of the interference of its own transmission signal to the outdoor base station or the neighboring indoor base station located around. In this case, the maximum transmission power may be changed to an appropriate value.

Then, each indoor base station periodically receives a CINR value from the terminal during operation.

At this time, if the feedback CINR value does not exceed the minimum value (CINR_min), normal service is not possible for the corresponding terminal. Therefore, each indoor base station adjusts the transmission power so that the CINR of the serving terminal exceeds the minimum value, CINR_min.

 On the other hand, if the channel state information exceeds the minimum value CINR_min, the current transmission power is maintained.

Here, the adjustment of the transmission power is performed through the following [Equation 4].

와

의 값은 적절한 값으로 정한다. 예를 들어,

=1,

=1의 값으로 정하면 전송파워를 증가시킬 수 있다. 다른 예로,

=0의 값으로 정하고,

의 값을 목표하는 CINR 값(CINR_target)으로 정할 수도 있다.The base station can adjust the power by repeating [Equation 4] L (L = 1, 2, 3, ...) times,

Wow

Is set to an appropriate value. E.g,

= 1,

Setting the value to = 1 can increase the transmission power. As another example,

Set to a value of 0,

May be set as a target CINR value (CINR_target).

At this time, if the transmission power is greater than the maximum transmission power (Ptx_max) it can no longer increase its own transmission power, and requests the transmission power of the adjacent indoor base station through the Internet backbone network. That is, a request is made to reduce transmission power to an adjacent indoor base station.

The neighboring indoor base station then lowers its transmission power to reduce the interference effect on the neighboring cell.

At this time, if the current CINR is lower than the CINR_min of the cell, smooth service is not possible, and thus the level is maintained above a certain level even after power adjustment. That is, the transmission power is reduced only when the current CINR is larger than (CINR_min + a).

,

) 조절을 통해서 전송파워의 감소를 수행한다. 예를 들어,

=0,

=1로 정하면 알고리즘을 수행할 때마다 전송파워가 감소한다.In addition, the transmission power is adjusted by using Equation 4 above, and the transmission power is adjusted by repeating L (L = 1, 2, 3, ...) times. At this time, the parameter of [Equation 4]

,

Adjust the power to reduce the transmission power. E.g,

= 0,

If set to = 1, the transmission power decreases every time the algorithm is executed.

Meanwhile, when the outdoor base station and the indoor base station use the same frequency, the outdoor base station and the indoor base station have the influence of interference with each other.

Therefore, the indoor base station should minimize the effect of interference on the terminal that was receiving services from the outdoor base station. That is, the maximum transmission power of the indoor base station is set so as not to significantly affect the outdoor base station.

In addition, the base station transmission power level in the actual communication system has a characteristic that is not continuous (Discrete). The transmission power adjustment for such a discontinuous transmission power level can be implemented by the following method.

First, the transmission power is determined through the continuous transmission power adjusting method described above. The signal is transmitted by selecting a value closest to the value (the determined transmission power value) among the discontinuous power levels.

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of recording medium that can be read by a computer.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

The present invention can be used for a portable internet system and the like.

1 is a configuration diagram of an embodiment of a portable Internet system composed of an outdoor / indoor base station to which the present invention is applied;

2 is an exemplary view of cell coverage between indoor base stations in a mobile Internet system to which the present invention is applied;

3 is an exemplary view of an indoor base station network of a portable Internet system to which the present invention is applied;

4 is a flowchart illustrating a method for adjusting a transmission power in an indoor portable Internet base station according to the present invention.

* Explanation of symbols for the main parts of the drawings

101: outdoor base station 102, 104: terminal

103: indoor base station

Claims (6)

In the transmission power control method in an indoor base station, Storing a minimum value and a maximum value corresponding to the channel state information; And Adjusting the transmission power so that the channel state information from the terminal is located between the minimum value and the maximum value, if the maximum transmission power exceeds the transmission power control step of requesting the transmission power reduction to the adjacent indoor base station through the communication network Transmission power control method in an indoor base station comprising a. The method of claim 1, Transmitting the signal by selecting a value closest to the determined transmission power value among the discontinuous power levels after determining the transmission power through the transmission power adjusting method; Transmission power control method in an indoor base station further comprising. delete The method according to claim 1 or 2, The transmission power adjustment step, Transmission power control method in an indoor base station for controlling the transmission power through the following [Equation A]. Equation A

(here,

Denotes transmission power transmitted from the i th base station to the k th time slot,

Indicates channel status information fed back from the cell.

Wow

Is an adjustable value with a positive real number.) The method of claim 4, wherein The transmission power adjustment step,

= 1,

If = 1, the transmission power is increased.

= 0,

A transmission power adjusting method in an indoor base station in which transmission power is reduced when = 1. delete

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