KR20090004370A - Apparatus and method for setting transmission power of compact base station in wireless communication system - Google Patents

Abstract

An apparatus for setting the transmission power of a small-sized base station and a method therefor are provided to enable the small-sized base station to optimize the transmission power adaptively according to the state of an external base station. A small-sized base station operates in a terminal mode to scan neighboring base stations(201), measures the signal strength and thermal noise of the scanned neighboring base stations(203,205), and then selects the biggest value on the measured results(207) to set a target RSSI by adding a setup value to the selected result. The small-sized base station is converted into a general base station mode to communicate with terminals belonging to a coverage area(209), transmits a scan instruction message to the terminals within its coverage area(211), receives a scan report message including the scanning result from the terminals(213), and then selects the maximum value from the signal strengths of neighboring base stations which at least one terminal reports to set the selected maximum value as the maximum RSSI(215). Finally, the small-sized base station compares whether the maximum RSSI is identical to the target RSSI(217), if the RSSIs are different, determines whether the maximum RSSI is bigger than the target RSSI(219), and if so, reduces the transmission power by the set value(221).

Description

Apparatus and method for setting transmission power of small base station in wireless communication system {APPARATUS AND METHOD FOR SETTING TRANSMISSION POWER OF COMPACT BASE STATION IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a small base station of a wireless communication system, and more particularly, to an apparatus and method for setting the transmission power of a small base station in a broadband wireless communication system.

In a cellular broadband wireless communication system, each of a plurality of base stations communicates with a terminal located in its cell area through a wireless channel. At this time, the state of the wireless channel changes as the terminal moves. If the terminal is located in a physically enclosed area, for example, an electric wave shadow area such as an office or a home, the channel situation between the base station and the terminal becomes very poor, and thus smooth communication cannot be achieved. Therefore, as an alternative to solve this problem, a method of installing a compact base station acting as a base station in a small indoor shadow area such as an office or a house has been considered.

That is, the small base station may be used in two cases as follows. First, a user cannot receive a service from an external base station installed by an operator due to attenuation due to an outer wall or an obstacle of a building. Second, a user installs a base station directly in a home or office for a low rate.

Unlike a large power base station installed by a service provider, such a small base station must adaptively adjust its transmission power according to a radio wave environment at a corresponding installation location. At this time, the transmission power of the small base station should provide a certain data transmission rate to the indoor user while minimizing interference with the existing system. In addition, handover with an external base station should be possible within the range allowed by the transmission power of the small base station.

Conventional code division multiple access (CDMA) small base stations, called ubicells, use a power ranging technique that increases transmission power until a foreign user is detected. That is, a device identifier (MAC address or ESN, etc.) of an indoor user is registered in a small base station installed indoors, and the small base station increases transmission power until an initial access or handover of an unregistered user is detected. To adjust the output.

However, such a conventional technique requires the small base station to know all registered users. When the small base station is installed in the home, there are few registered users, so the implementation burden is small. However, when the small base station is installed in a large business building, there is a problem that it is difficult to implement too many registered users. In addition, when a foreign user enters the building, it should be recognized as an exception and perform a process that does not change the transmission power. That is, there is a problem in that an external user's connection (or handover) is due to indoor entry or excessive output of an indoor base station.

As such, adjusting the transmission power of the small base station by detecting the connection (or handover) of the external user is not only necessary for the registration of the internal user but also cannot accurately determine whether the connection of the external user is due to indoor entry. There is a difficulty in implementation.

Accordingly, an object of the present invention is to provide an apparatus and method for efficiently setting a transmission power in a small base station of a wireless communication system.

Another object of the present invention is to provide an apparatus and method for setting transmission power using signal strengths of neighboring base stations reported by a terminal in a small base station of a wireless communication system.

Another object of the present invention is to provide an apparatus and method for setting a transmission power by comparing the signal strength of the neighboring base station measured through the terminal mode and the signal strength of the neighboring base station reported from the terminal in a small base station of the wireless communication system have.

Another object of the present invention is to set the target strength using the signal strength of the neighboring base station measured through the terminal mode in the small base station of the wireless communication system, the transmission power so that the signal strength of the neighboring base station reported from the terminal is the target strength It is to provide an apparatus and method for adjusting the.

Another object of the present invention is to provide an apparatus and method for estimating and compensating shadowing in a small base station of a wireless communication system.

Another object of the present invention is to define the difference between the signal intensity average value of the small base station measured in the terminal in the small base station of the wireless communication system and the signal intensity average value of the external base station measured in the same terminal as the power rise value, the power An apparatus and method for adjusting a transmission power such that a rising value is a target value is provided.

According to an aspect of the present invention for achieving the above object, in a small base station in a wireless communication system, the measuring unit for measuring the signal strength of the neighboring base station during operation in the terminal mode, and the signal strength of the neighboring base station measured by the terminal And a self-configuring control unit configured to set a transmission power using the signal strength of the neighboring base station measured through the terminal mode and the signal strength of the neighboring base station reported from the terminal.

According to another aspect of the present invention, in a method for setting a transmission power of a small base station in a wireless communication system, measuring the signal strength of the neighboring base station while operating in the terminal mode, and receives the signal strength of the neighboring base station measured by the terminal And setting the transmission power by using the signal strength of the neighboring base station measured through the terminal mode and the signal strength of the neighboring base station reported from the terminal.

According to still another aspect of the present invention, in a small base station in a wireless communication system, the measurement unit for measuring the signal strength of the external base station during operation in the terminal mode, and the signal strength of the small base station and the external base station measured in the terminal Estimating shadowing by using a receiving receiver and an average value of signal strengths of external base stations reported from terminals, and compensating the estimated shadowings for signal strengths of external base stations measured through the terminal mode, And a self-configuring control unit for adding the signal strengths of the shadow-compensated external base station to obtain the sum of interference signals.

According to still another aspect of the present invention, a method of operating a small base station in a wireless communication system, the method of measuring the signal strength of the external base station during operation in the terminal mode, and the signal strength of the small base station and the external base station from the terminals In the process of receiving the report, calculating the average value of the signal strength of the external base station reported from the terminals, estimating shadowing using the average value, and the signal strength of the external base station measured through the terminal mode Compensating for the estimated shadowing for the estimated, and adding the signal strength of the shadowing compensated external base station to calculate the sum of the interference signal, and the sum of the noise and the interference signal measured through the terminal mode In addition, obtaining an NI value, and calculating the average value by averaging the signal strength of the small base station reported from the terminals by dB And subtracting the NI value (unit: dB) from the calculated average value to calculate a power rise, and adjusting the transmission power by comparing the power rise value with a target value. Characterized in that.

As described above, the small base station according to the present invention has an advantage of adaptively optimizing the transmission power according to the state of the external base station. In addition, the present invention adjusts the transmission power by using the signal strength of the neighboring base station reported from the terminal, there is an advantage that it is easy to implement. That is, the external base station does not need any change for the implementation of the present invention, and since the terminal also needs to report the signal strength of the adjacent base station to the small base station according to the specification, there is an advantage that it can be easily performed without modification of the system.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, a description will be given of a technique for adaptively setting a transmission power in a small base station of a wireless communication system.

In the following description, the wireless communication system is, for example, a communication system using an Orthogonal Frequency Division Multiplexing (OFDM) scheme or an Orthogonal Frequency Division Multiple Access (OFDMA) scheme. That is, the following description describes a broadband wireless access communication system using multiple carriers as an example, but the present invention can be equally applied to other wireless communication systems using a small base station.

Here, the small base station is a low-power base station directly installed by the user, such as a micro base station, a self configurable base station, a compact base station, an indoor base station, a home base station, and the like. Can be called.

1 shows a configuration of a wireless communication system using a small base station according to the present invention.

As shown, the wireless communication system includes a large base station 100, a small base station 110, and a network manager 120. The large base station 100 represents a large output general base station installed outdoors. The small base station 110 is a low power micro base station installed indoors. In addition, the small base station 110 is a self-configurable base station that optimizes its own operating parameters (operation parameters) when plugged in. For the optimization, the small base station 110 operates in a terminal mode to measure a surrounding situation (radio state, etc.). Thus, a mode of operating as a terminal as necessary is called an over-the-air receiver (OTAR) mode. Shall be. The network manager 120 is responsible for network optimization such as setting of a system such as IP (Internet Protocol) setting of base stations and image download, and monitoring and managing the status of operating base stations. The network manager 120 may be referred to as a WiBro System Manager (WSM) or an Element Management System (EMS).

2 illustrates an operation procedure of a small base station in a broadband wireless communication system according to an embodiment of the present invention. The algorithm described below relates to transmission power optimization among self-configuration functions of a small base station.

Referring to FIG. 2, first, a small base station operates in a terminal mode (error mode) in step 201 to scan adjacent base stations by a periodic or specific event. During the terminal mode, the small base station measures the signal strength of the neighboring base station received in step 203 and measures the thermal noise in step 205.

In step 207, the small base station selects the largest value among the measured signal strengths of the neighboring base stations and the thermal noise, and sets a 'target RSSI' by adding a power rise value to the selected value. That is, the target RSSI is set using the RSSI value of the neighboring base station which has the greatest influence at the current location. In this case, the thermal noise may be greater than the RSSI value of the neighboring base station. In this case, the target RSSI is set using the thermal noise. That is, the target RSSI is calculated through the following equation.

Target RSSI (dBm) = Max (thermal noise (dBm), Max.RSSI _OTAR (dBm)) + Power Rise (dB)

Here, Max.RSSI _OTAR represents the largest value among the signal strengths of neighboring base stations measured through the terminal mode, and Power Rise is a value that is optimized by simulation in order to ensure cell coverage of the small base station.

After setting the target RSSI, the small base station switches to the normal base station mode in step 209 to communicate with terminals belonging to the coverage area. After switching to the normal base station mode, the small base station transmits a scan instruction message (eg, MOB_SCN-RSP) requesting scanning to the terminals in its coverage area in step 211. The scan indication message may include information of neighbor base stations to be scanned. If the neighboring base station uses a different frequency from the small base station, the small base station should allocate a separate scan interval for an inter-FA scan through the scan indication message.

In step 213, the small base station receives a scan report message (eg, MOB_SCN-REP) including a scanning result from the terminals. The scan report message may include an identifier and a scanning result (RSSI) for each of the neighbor base stations recognized through scanning.

In step 215, the small base station selects the maximum value among the signal strengths of the neighbor base stations reported from the at least one terminal and sets the maximum value to 'maximum RSSI'.

In step 217, the small base station compares the maximum RSSI with the target RSSI. At this time, if the maximum RSSI and the target RSSI are the same, it is determined that transmission power adjustment is not necessary and the algorithm ends.

If the maximum RSSI and the target RSSI are different, the small base station proceeds to step 219 and determines whether the maximum RSSI is greater than the target RSSI. In this case, if the maximum RSSI is greater than the target RSSI, the small base station proceeds to step 221 and reduces the transmission power by a set value and returns to step 211. That is, it is determined that the current transmission power excessively widens the cell coverage, thereby reducing the transmission power.

On the other hand, if the target RSSI is the maximum RSSI, the small base station proceeds to step 223 and increases the transmission power by a set value and returns to step 211. That is, it is determined that the current transmission power does not secure a predetermined cell coverage, thereby increasing the transmission power. As such, when a transmission power is increased or decreased, a hysteresis margin may be applied to prevent frequent fluctuations in the transmission power. For example, if the margin value is 1.0 dB, the transmission power can be adjusted only when the difference between the target RSSI and the maximum RSSI is 1.0 dB or more.

Although the algorithm of FIG. 2 described above is simple, performance deterioration may occur because shadowing at the installation location of the small base station and shadowing according to the terminal location are not considered. Therefore, another embodiment of the present invention that can compensate for the performance degradation due to the shadowing will be proposed.

According to another embodiment of the present invention, the small base station first performs an OTAR mode to measure signal strength and thermal noise of the external base station. In addition, during the normal mode, the small base station continuously observes the received signal strength indicator (RSSI) of the external base station reported from the terminal, calculates a power rise value, and calculates the calculated power rise value. The transmission power of the small base station is changed by comparing the target power rise with the set target power rise. At this time, the dB average value of the RSSI value of the small base station measured by the terminal and the average value of the RSSI value of the RSSI value of the external base station measured by the same terminal is obtained, and the difference is determined as the power rise value. This is expressed as Equation 1 as an expression.

However, it was experimentally confirmed that the power increase value has a constant value until the coverage of the indoor base station (small base station) reaches the building boundary regardless of the absolute size of the building. Assuming that the building transmission loss is larger than the change in the power rise value according to the shape of the building, such as a non-round rectangle and the attenuation model, the target power rise value can be fixed. Based on this assumption, the present invention increases the transmit power of the base station until the power increase value determined through the terminal report reaches the target power rise value.

On the other hand, the average value of the interference signal sum and the thermal noise (N) from the external base station (macro base station) on the right side of the equation (1) can use the value reported by the terminal, but in actual implementation it is measured by the base station in the typo mode It can be used by approximation. The reason for the approximation is that the installation position of the small base station is the center of the room. If the measured value is used in the typo mode, the shadowing value at the corresponding position should be estimated and compensated. The compensation algorithm is represented by Equation 2 below.

는 단말의 잡음 지수(noise figure)를 나타내고,

는 기지국의 잡음 지수를 나타내며,

는 잡음 스펙트럼 밀도(noise spectral density)를 나타내고,

는 대역폭(bandwidth)을 나타내며,

는 매크로 기지국(외부 기지국)의 인덱스를 나타내고,

는 j번째 매크로 기지국에서의 쉐도윙을 나타내며,

는 j번째 매크로 기지국에서 소형 기지국까지의 경로 손실(path loss)을 나타내고,

는 j번째 매크로 기지국의 송신 전력(transmit power)을 나타내며,

는 단말에서의 쉐도윙을 나타낸다. here,

Denotes a noise figure of the terminal,

Represents the noise figure of the base station,

Denotes the noise spectral density,

Denotes bandwidth,

Denotes the index of the macro base station (external base station),

Represents shadowing in the j-th macro base station,

Denotes a path loss from the j-th macro base station to the small base station,

Denotes the transmit power of the j-th macro base station,

Represents shadowing in the terminal.

The first equation in Equation 2 represents the sum of noise and interference at the small base station location. As shown in the second equation, noise power can be estimated through a typo operation and the shadowing of the small base station can be compensated. At this time, the shadowing compensation is the same as the third equation. That is, since the small base station is located in the center of the room, the shadowing is estimated by calculating the difference in dB units of the maximum RSSI value of the external base station reported from the terminal from the value measured through the typo mode and using the estimated value To compensate. On the other hand, by averaging the RSSI values measured by the terminals in dB as in the last equation can also remove the shadowing effect for each terminal location.

Hereinafter, a detailed operation according to another embodiment of the present invention will be described with reference to the drawings.

3 is a flowchart illustrating an operation of a small base station in a broadband wireless communication system according to another embodiment of the present invention.

Referring to FIG. 3, a small base station scans an external base station by operating in a terminal mode (error mode) in step 301 by a periodic or specific event. During the terminal mode, the small base station measures the signal strength of the received external base station and measures the thermal noise.

In step 303, the small base station determines the external base station having the largest signal strength. In this case, it is assumed that the index (or identifier) of the external base station having the largest signal strength is j ₀ .

In this way, after determining the external base station that has the greatest impact with the small base station, the small base station proceeds to step 305 to switch to the normal base station mode to communicate with the terminals belonging to the coverage area. After switching to the normal base station mode, the small base station transmits a scan instruction message (eg, MOB_SCN-RSP) requesting scanning to terminals in its coverage area (307). The scan indication message may include information of at least one base station to be scanned. Here, it is assumed that the small base station requests scanning of itself (SC-RAS) and the j _0th external base station to the terminals. If the external base station uses a different frequency from the small base station, the small base station should allocate a separate scan interval for an inter-FA scan through the scan indication message.

In step 309, the small base station receives a scan report message (eg, MOB_SCN-REP) including a scanning result from the terminals. The scan report message may include a scanning result (RSSI) of the small base station and the j ₀ th external base station.

)을 구하고, 상기 적어도 하나의 단말로부터 보고된 상기 j₀번째 외부 기지국의 신호세기 값의 dB 평균값(

)을 구한다. 이와 같이, 단말들에서 측정된 RSSI 값들을 dB단위로 평균함으로써 단말 위치별 쉐도윙 영향을 제거한다.Then, the small base station is a dB average value of the signal strength (RSSI) value of the small base station reported from at least one terminal in step 311 (

), And the dB average value of the signal strength value of the j ₀ th external base station reported from the at least one terminal (

) As such, the shadowing effect for each terminal location is removed by averaging RSSI values measured by the terminals in dB units.

를 이용해서 자신의 위치에서의 쉐 도윙(

)을 추정한다.In addition, the small base station measures the signal strength of the j ₀ th external base station measured in the typo mode in step 313.

Using the

Estimate).

)에서 상기 쉐도윙 추정값(

)을 빼서 쉐도윙을 보상하고, 모든 기지국들에 대한 상기 쉐도윙 보상 값들을 모두 가산하여 간섭신호의 합(

)을 구한다.In step 315, the small base station measures the signal strength of the j-th external base station measured through the typo mode.

In the shadowing estimate (

) To compensate for shadowing, and add all the shadowing compensation values for all base stations to sum the interference signal (

)

)을 가산하여 간섭신호와 열잡음의 합(

)을 구한다. In step 317, the small base station sums the thermal noise N and the interference signal measured through the error mode.

) To add the interference signal and the thermal noise (

)

)에서 상기 간섭신호의 열잡음의 합(

)을 감산하여 전력상승(Power Rise) 값을 계산한다.In step 319, the small base station measures the dB average value of the signal strength values of the small base station measured by the terminals.

Sum of thermal noise of the interference signal

Calculate Power Rise value by subtracting).

In operation 321, the small base station compares the calculated power rise value with a target power rise. If the calculated power increase value is smaller than the target value, the small base station increases the transmission power by a set value in step 323 and returns to step 307. That is, it is determined that the current transmission power does not secure a predetermined cell coverage, thereby increasing the transmission power. If the calculated power increase value is larger than the target value, the small base station returns to step 307 after reducing the transmission power by a set value in step 325. That is, it is determined that the current transmission power excessively widens the cell coverage, thereby reducing the transmission power.

As such, when a transmission power is increased or decreased, a hysteresis margin may be applied to prevent frequent fluctuations in the transmission power. For example, if the margin value is 1.0 dB, the transmission power can be adjusted only when the difference between the measured power rise value and the target value is 1.0 dB or more.

4 is a block diagram of a small base station in a broadband wireless communication system according to an exemplary embodiment of the present invention. Hereinafter, a description will be made on the assumption of a time division duplexing (OFD) -OFDMA system. However, the present invention can be easily applied to any system that performs power control, such as a frequency division duplexing (FDD) -OFDMA system, a hybrid system using TDD and FDD together.

As shown, the small base station according to the present invention, the MAC (Media Access Control) layer 400, the transmission modem 402, the RF transmitter 404, the duplexer 406, the RF receiver ( 408, the reception modem 410, and the self-configuration controller 416.

Referring to FIG. 3, first, the MAC layer unit 400 receives transmission data from an upper layer (eg, an IP layer unit), processes the transmission data according to a connection method with the transmission modem 402, and transmits the transmission data. Forward to modem 404. Then, the reception data is received from the reception modem 410, the received data is processed according to a connection method with a higher layer, and transferred to the higher layer.

In addition, according to the present invention, the MAC layer unit 400 provides information necessary for self configuration to the self configuration controller 416. The present invention relates to transmission power setting among the self-configuring functions. In order to set the transmission power, the present invention requires a signal strength value of a neighbor base station (small base station and an external base station) reported from a terminal, and the MAC layer unit 400 receives a message (for example, a scan report message) received from the terminal. The signal strength value of the neighboring base station is extracted from the self-configuration controller 416. Here, the signal strength may be RSSI (Received Signal Strength Indicator), Signal to Interference and Noise Ratio (SINR), Signal to Noise Ratio (SNR), Carrier to Interference and Noise Ratio (CINR), etc. Let's take a look at RSSI as an example.

The transmission modem 402 physically encodes and outputs a packet (data burst) from the MAC layer unit 400. Here, the transmission modem 402 may be composed of a channel encoder, a modulator, and an inverse fast fourier transform (IFFT).

The RF transmitter 404 includes a frequency converter, a filter, an amplifier, and the like. The RF transmitter 404 converts the baseband data from the transmission modem 402 into an analog signal and converts the baseband analog signal into an RF signal and outputs the RF signal. At this time, the RF transmitter 404 adjusts and transmits transmission power according to a control signal (transmission power control signal) from the self-configuration controller 416.

The duplexer 406 transmits the received signal from the antenna to the RF receiver 408 by the duplexing method, and transmits the transmitted signal from the RF transmitter 404 to the antenna.

The RF receiver 408 includes an amplifier, a frequency converter, a filter, and the like, converts an RF signal from the duplexer 406 into a baseband signal, and converts an analog baseband signal into digital data and outputs the digital data.

The reception modem 410 physically decodes and outputs the data from the RF receiver 408. Here, the reception modem 410 may be configured of a fast fourier transform (FFT), a demodulator, a channel decoder, and the like. In addition, the reception modem 410 includes a signal strength measuring unit 412 that can measure the strength (RSSI) of the received signal and a noise measuring unit 412 that can measure the thermal noise (Thermal Noise).

The signal strength measuring unit 412 measures the signal strength (RSSI) of the adjacent base station (including the external base station) received when the terminal mode (operation mode) in operation, and provides it to the self-organizing control unit 416. In addition, the noise measuring unit 412 measures the thermal noise when operating in the terminal mode and provides it to the self-organizing control unit 416.

The self-configuration control unit 416 performs a function of optimizing operation parameters required for the operation of the small base station. For example, the operation parameter may be a frequency allocation (FA), a segment ID, a cell ID (IDentifier), a transmission power, or the like. The present invention relates to the transmission power setting, which will be described in detail below.

Looking at the transmission power control according to an embodiment of the present invention.

First, the self-configuration controller 416 operates the small base station in a terminal mode (error mode) to scan an adjacent base station. While operating in the terminal mode, the signal strength measuring unit 412 measures the signal strength of neighboring base stations and provides it to the self-organizing control unit 416, and the noise measuring unit 414 measures the thermal noise Provided to the configuration control unit 416. Then, the self-configuration controller 416 selects the maximum value of the signal strengths of the neighboring base stations and the thermal noise, and sets a 'target RSSI' by adding a power rise value to the selected maximum value. Here, the set value is a value for ensuring cell coverage of the small base station, which is optimized through simulation.

After setting the target RSSI, the self-configuration controller 416 switches the small base station to the normal base station mode. While operating in the normal mode, the small base station transmits a scan instruction message (eg, MOB_SCN-RSP) requesting scanning to the terminal and receives a scan report message (eg, MOB_SCN-REP) including the scanning result. . That is, the MAC layer 400 analyzes the scan report message received from the terminal, extracts the signal strength of the neighboring base station measured by the terminal, and provides the signal strength of the neighboring base station to the self-configuring controller 416. . The self-configuration controller 416 selects a maximum value among signal strengths of neighbor base stations reported from at least one terminal, and sets the maximum value to 'maximum RSSI'.

The self-configuration controller 416 compares the target RSSI with the maximum RSSI to determine an increase or decrease of transmission power, and provides the transmission power control signal to the transmission modem 402 or the RF transmitter 404. . At this time, if the maximum RSSI is larger than the target RSSI, the cell coverage is excessively increased, and thus, the transmission power is reduced. On the contrary, if the target RSSI is large, the transmission power is increased because the coverage of the small base station must be secured.

Looking at the transmission power control according to another embodiment of the present invention.

First, the self-configuration controller 416 operates the small base station in a terminal mode (error mode) to scan an external base station. While operating in the terminal mode, the signal strength measuring unit 412 measures the signal strength of external base stations and provides it to the self-organizing control unit 416, and the noise measuring unit 414 measures the thermal noise Provided to the configuration control unit 416. Then, the self-configuration controller 416 selects an external base station (j ₀ th external base station) having the largest value among the signal strengths of the external base stations.

Thereafter, the self-configuration controller 416 switches the small base station to the normal base station mode. While operating in the normal mode, the small base station transmits a scan command message (eg MOB_SCN-RSP) requesting scanning to the terminal and receives a scan report message (eg MOB_SCN-REP) including the scanning result. do. In this case, the self-configuring controller 416 may obtain a scanning result (RSSI) of the terminals for the small base station and the j ₀ th external base station.

The self-organizing control unit 416 is a dB average value (first average value) of the signal strength value of the small base station reported from the terminals and the dB average value (signal value of the j ₀ th external base station reported from the terminals) (second Average value). The self-configuring controller 416 estimates shadowing at the location of the small base station using the second average value, and uses the signal strength of the external base stations measured through the error mode and the shadowing estimate using the shadowing estimate. Find the sum of (I). Thereafter, the self-organizing control unit 416 obtains NI by adding the sum of thermal noise (N) and the interference signal (I) measured through the error mode, and subtracts the NI from the first average value to increase the power increase value. Obtain

As described above, after obtaining the power rise value, the self-organizing control unit 416 compares the power rise value with a target power rise to determine the increase and decrease of the transmit power, and transmits the transmit power control signal to a transmit modem ( 402 or the RF transmitter 404. At this time, if the power increase value is greater than the target value, the cell coverage is excessively increased, and thus the transmission power is reduced.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described. However, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a diagram showing a schematic configuration of a broadband wireless communication system according to the present invention;

2 is a diagram illustrating an operation procedure of a small base station in a broadband wireless communication system according to an embodiment of the present invention.

3 is a diagram illustrating an operation procedure of a small base station in a broadband wireless communication system according to another embodiment of the present invention.

4 is a diagram illustrating a configuration of a small base station in a broadband wireless communication system according to an embodiment of the present invention.

Claims (35)

In a small base station in a wireless communication system, A measuring unit measuring signal strength of an adjacent base station while operating in a terminal mode; A receiver for receiving the signal strength of the neighboring base station measured by the terminal; And a self-configuring controller configured to set a transmission power by using the signal strength of the neighboring base station measured through the terminal mode and the signal strength of the neighboring base station reported from the terminal. The method of claim 1, wherein the self-organizing control unit, Setting a target strength using the signal strength of the neighboring base station measured through the terminal mode, and adjusting the transmission power so that the signal strength of the neighboring base station measured by the terminal and reported to the small base station becomes the target strength. Small base station characterized. The method of claim 1, wherein the self-organizing control unit, The target strength is set by adding a set value to the maximum value of the signal strengths of the neighboring base stations measured through the terminal mode, and the maximum value of the signal strengths of the neighboring base stations reported from the terminals is maximized. And the transmission power is adjusted by comparing the target intensity with the maximum intensity. The method of claim 3, The setting value is a small base station, characterized in that for securing the cell coverage of the small base station. The method of claim 3, wherein the self-organizing control unit, And the transmission power is decreased when the maximum intensity is greater than the target intensity, and the transmission power is increased when the target intensity is greater than the maximum intensity. The method of claim 3, wherein the self-organizing control unit, And when the difference between the maximum intensity and the target intensity is greater than or equal to a set margin, the small base station. The method of claim 1, The signal strength of the adjacent base station is small, characterized in that one of the Received Signal Strength Indicator (RSSI), Carrier to Interference and Noise Ratio (CINR), Signal to Interference and Noise Ratio (SINR), Signal to Noise Ratio (SNR) Base station. The method of claim 1, The small base station further comprises a measurement unit for measuring the thermal noise during operation in the terminal mode. The method of claim 8, wherein the self-organizing control unit, The target strength is set by using the largest value of the signal strength of the neighboring base stations measured through the terminal mode and the measured thermal noise, and the transmission power is set such that the signal strength of the neighboring base station reported from the terminal becomes the target strength. Small base station, characterized in that for adjusting. The method of claim 1, The small base station further comprises a transmitter for transmitting a neighbor base station scanning instruction to the terminal. In the transmission power setting method of a small base station in a wireless communication system, Measuring the signal strength of a neighboring base station while operating in a terminal mode; Receiving a signal strength of the neighboring base station measured by the terminal; And setting a transmission power by using the signal strength of the neighboring base station measured through the terminal mode and the signal strength of the neighboring base station reported from the terminal. The method of claim 11, wherein the setting process, Setting a target strength using the signal strength of the neighboring base station measured through the terminal mode; And adjusting the transmission power so that the signal strength of the neighboring base station reported from the terminal becomes the target strength. The method of claim 11, wherein the setting process, Setting a target intensity by adding a set value to a maximum value among signal strengths of neighboring base stations measured through the terminal mode; Setting the maximum value of the signal strengths of neighboring base stations reported from the terminals to the maximum strength; And adjusting the transmission power by comparing the target intensity with the maximum intensity. The method of claim 13, The setting value is a value for ensuring cell coverage of the small base station. The method of claim 13, wherein the adjusting process, Reducing the transmission power when the maximum intensity is greater than the target intensity; And if the target intensity is greater than the maximum intensity, increasing the transmit power. The method of claim 13, wherein the adjusting process, And when the difference between the maximum intensity and the target intensity is greater than or equal to a set margin, changing the transmission power. The method of claim 11, The signal strength of the adjacent base station is one of the following: Received Signal Strength Indicator (RSSI), Carrier to Interference and Noise Ratio (CINR), Signal to Interference and Noise Ratio (SINR), Signal to Noise Ratio (SNR) . The method of claim 11, And measuring thermal noise while operating in the terminal mode. The method of claim 18, wherein the setting process, Setting a target intensity by adding a set value to a maximum value of the signal strength of the neighboring base stations measured through the terminal mode and the measured thermal noise; And adjusting the transmission power so that the signal strength of the neighboring base station reported from the terminal becomes the target strength. The method of claim 11, And transmitting a neighbor base station scanning instruction to the terminal. In a small base station in a wireless communication system, A measurement unit for measuring signal strength of an external base station while operating in a terminal mode; A receiver for receiving signal strengths of the small base station and the external base station measured by the terminal; Estimating shadowing by using the average value of the signal strength of the external base station reported from the terminals, compensating the estimated shadowing for the signal strength of the external base station measured through the terminal mode, the shadowing compensated A small base station comprising a self-configuring control unit for adding the signal strength of the external base station to obtain the sum of the interference signals. The method of claim 21, The self-configuring control unit, the small base station characterized in that the average value of the signal strength of the external base station that has the largest impact on the small base station among the signal strength of the external base station reported from the terminal to obtain the average value. The method of claim 22, The self-configuring control unit, the small base station to estimate the shadowing by subtracting the average value from the signal strength of the external base station having the largest value among the signal strength of the external base station measured in the terminal mode. The method of claim 21, The self-configuring control unit compensates for shadowing by subtracting the measured shadowing value (unit: dB) from signal strength (unit: dB) for each of the external base stations measured through the terminal mode. Small base station. The method of claim 21, The self-configuring control unit is a small base station, characterized in that to obtain the NI value by adding the sum of the noise and the interference signal measured in the terminal mode. The method of claim 25, The self-organizing control unit averages the signal strengths of the small base stations reported from the terminals by dB and averages the average value (

) And subtracting the NI value (unit: dB) from the average value to obtain a power rise. The method of claim 26, The self-configuring controller compares the power increase value with a target value, and when the power rise value is greater than the target value, decreases the transmission power of the small base station and increases the transmission power if it is smaller than the target value. Small base station characterized. In the method of operating a small base station in a wireless communication system, Measuring the signal strength of an external base station while operating in a terminal mode; Receiving signal strengths of the small base station and the external base station from terminals; Calculating an average value of signal strengths of the external base stations reported from the terminals; Estimating shadow wing using the average value; Compensating the estimated shadow wing for the signal strength of the external base station measured through the terminal mode; And calculating the sum of interference signals by adding all the signal strengths of the shadow-compensated external base station. The method of claim 28, wherein the average value calculation process, The average value is obtained by averaging the signal strengths of the external base station having the largest influence on the small base station among the signal strengths of the external base station reported from the terminals. The method of claim 29, wherein the shadow wing estimation process, And estimating the shadowing by subtracting the average value from the signal strength of the external base station having the largest value among the signal strengths of the external base station measured through the terminal mode. The method of claim 28, wherein the shadow wing compensation process, And subtracting the measured shadowing value (unit: dB) from the signal strength (unit: dB) for each of the external base stations measured through the terminal mode. The method of claim 28, And adding the sum of the noise measured through the terminal mode and the interference signal to obtain an NI value. 33. The method of claim 32, The average value of the signal strength of the small base station reported from the terminals by dB averaged (

), And subtracting the NI value (dB) from the calculated average value to calculate a power rise. The method of claim 33, wherein Comparing the power increase value with a target value; Reducing the transmit power of the small base station if the power rise value is greater than the target value, and increasing the transmit power if the power rise value is less than the target value. In the method of operating a small base station in a wireless communication system, Receiving signal strengths of the small base station and the external base station from terminals; Obtaining a first average value by averaging the signal strengths of the small base stations reported from the terminals by dB; Obtaining a second average value by averaging the signal strengths of the external base stations reported from the terminals by dB; Obtaining a power increase value by subtracting the second average value from the first average value; And controlling a transmission power to become the power rise value and the target value.

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