KR20080037150A - Apparatus and method for selecting of frequency band in broadband wireless communication system - Google Patents

Abstract

An apparatus and a method for selecting a frequency band in a broadband wireless communication system are provided to determine a frequency allocation band and transmission power in consideration of signals of adjacent base stations, thereby optimizing frequency allocation and transmission power even without additive facilities. A transmission and reception switch(203) converts a transmission mode or a reception mode inversely so as to receive signals of adjacent base stations. A frequency selector(225) selects a frequency allocation band, considering the signals received from the adjacent base stations. A transmission power-determining unit(227) determines a signal transmission power in the frequency allocation band. The transmission and reception switch is a TDD(Time Division Duplex) type switch.

Description

Apparatus and method for selecting a frequency band in a broadband wireless communication system {APPARATUS AND METHOD FOR SELECTING OF FREQUENCY BAND IN BROADBAND WIRELESS COMMUNICATION SYSTEM}

1 is a diagram schematically showing a broadband wireless communication system according to the present invention;

2 is a block diagram of a base station in a broadband wireless communication system according to the present invention; and

3 is a diagram illustrating a procedure for determining an operating frequency band and signal strength by a base station in a broadband wireless communication system according to an exemplary embodiment of the present invention.

The present invention relates to a broadband wireless communication system, and more particularly, to an apparatus and method for determining an operating frequency band of a base station in a broadband wireless communication system.

In the 4th Generation (hereinafter referred to as '4G') communication system, which is a next generation communication system, active researches are being conducted to provide users with services having various service qualities having a transmission rate of about 100 Mbps. In particular, the current 4G communication system to support high-speed services in the form of guaranteeing mobility and quality of service (QoS) for broadband wireless access communication systems such as wireless local area network network system and wireless urban area network system Research is being actively conducted. In addition, the representative communication system is the Institute of Electrical and Electronics Engineers (IEEE) 802.16 communication system.

The IEEE 802.16 communication system includes Orthogonal Frequency Division Multiplexing (hereinafter, referred to as OFDM) and Orthogonal Frequency Division Multiple Access to support a broadband transmission network on a physical channel of the wireless communication system. A communication system employing the following OFDMA) scheme. In the IEEE 802.16 communication system, research is being actively conducted to secure mobility of a terminal and flexibility of a wireless network configuration, and to provide a more efficient service in a wireless environment in which traffic distribution or call demand is changed.

A communication system having a frequency reuse rate of 2 or more based on the IEEE 802.16 should appropriately allocate frequency resources in units of base stations when designing a system. That is, prior to installing the communication system, optimization work for frequency allocation must be preceded. Since the optimization work has to consider various factors, the optimization work is very burdensome when considering a small-scale communication network. Therefore, in order to reduce the burden on the optimization operation, the base station receives a signal from the neighbor base station using an external terminal device, and obtains the operating frequency band and the received signal strength of the neighbor base station by using the received signal Optimization work was performed. However, the method using the external terminal device also causes an increase in cost and acts as a large overhead.

Accordingly, an object of the present invention is to provide an apparatus and method for reducing the cost increase and overhead due to the optimization of frequency allocation when configuring a communication network in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for determining an operating frequency band of a base station when configuring a communication network in a broadband wireless communication system.

Another object of the present invention is to provide an apparatus and method for determining a transmission power of a base station in a communication network in a broadband wireless communication system.

According to a first aspect of the present invention for achieving the above object, a base station apparatus of a broadband wireless communication system, a transmission and reception switch for switching the transmission and reception mode in reverse to receive a signal of the adjacent base stations, and received from the adjacent base stations And a transmission power determination unit for selecting an operating frequency band with reference to the signal, and a transmission power determination unit for determining signal transmission power in the frequency band.

According to a second aspect of the present invention for achieving the above object, a method for selecting an operating frequency band in a base station of a broadband wireless communication system, the process of receiving the signals of neighboring base stations by switching the transmission mode and the reverse; And selecting an operating frequency band according to the received signal strength from neighboring base stations, and determining the transmission power using the received signal strength in the operating frequency band.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, a description will be given of a technique for determining an operating frequency band and a transmission power of a base station in a broadband wireless communication system. In the following description, the wireless communication system is described using orthogonal frequency division multiplexing (OFDM) and time division duplex (hereinafter referred to as TDD) wireless communication systems as examples. The same can be applied to the base communication system. In the following description, it is assumed that the frequency reuse factor of the wireless communication system is 2 or more.

1 schematically illustrates a broadband wireless communication system according to the present invention.

Referring to FIG. 1, base station A 110 is a base station newly added to a communication network, and base station B 120 and base station C 130 are installed before the base station A 110 or an operating frequency band is already determined. And serving base station. In addition, the base station B 120 and the base station C 130 use the first frequency band and the second frequency band, respectively.

At this time, the base station A (110) receives the signals of the base station B (120) and base station C (130) by operating in the scan mode to determine the operating frequency band and transmission power. That is, the base station A 110 operates in the uplink mode while the neighboring base station operates in the downlink mode by inverting the TDD mode.

The base station A 110 checks the received signal strength for each frequency band of signals received from adjacent base stations including the base station B 120 and the base station C 130, and operates the frequency band having the lowest received signal strength. Select by band. For example, when the frequency band available in the communication system is only the first frequency band or the second frequency band, the base station A 110 has a low received signal strength among the base station B 120 or the base station C 130. Select the frequency band used by the base station. However, when the third frequency band is available, since the signal of the third frequency band is not received, it is determined that the signal has the lowest received signal strength and selects the third frequency band.

Thereafter, the base station A 110 measures a path loss with an adjacent base station using the selected frequency band, and determines the transmission power with reference to the measured path loss. Here, the path loss can be measured by decoding the control signal of the base station. If the signal from the corresponding base station is weak enough that decoding is impossible, the base station A 110 determines the transmission power as the maximum power available.

The description with reference to FIG. 1 schematically illustrates a system in which a base station determines an operating frequency band and a transmission power by itself. In the following description, a block configuration and an operation procedure of a base station for determining the operating frequency band and transmission power will be described in detail.

2 is a block diagram of a base station in a broadband wireless communication system according to the present invention.

As shown in FIG. 2, the base station includes a filter 201, a TDD switch 203, a low noise amplifier (LNA) 205, a radio frequency (RF) processor 207, and an analog. Digital-to-digital converter (hereinafter referred to as ADC) 209, OFDM demodulator 211, demodulator and decoder 213, encoding and modulator 215, OFDM modulator 217, digital-to-analog converter An analog converter (hereinafter referred to as a DAC) 219, an RF processor 221, a power amplifier (PA) 223, a frequency determiner 225, and a transmit power determiner 227.

The filter 201 is a band-pass filter, and removes signals outside the frequency band to be transmitted or received. In particular, when the base station switches to the scan mode according to the present invention, the signals of all bands that can be transmitted are passed.

The TDD switch 203 determines transmission or reception of the base station according to a predetermined time interval. That is, it operates in the transmission mode in the downlink frame period and in the reception mode in the uplink frame period. In particular, according to the present invention, when the scan mode is switched, it operates in a reception mode to receive a transmission signal of an adjacent base station during the downlink frame period.

The low noise amplifier 205 amplifies the power of the attenuated received signal through the wireless channel. The RF processor 207 converts an RF band signal into a baseband signal. The ADC 209 receives an analog signal and converts it into a digital signal. The OFDM demodulator 211 receives a time-domain signal and performs a fast fourier transform (FFT) operation to convert the signal into a frequency-domain signal. The demodulator and decoder 213 demodulates and decodes a complex symbol in a corresponding manner to restore data.

The encoder and modulator 215 receives the data, encodes and modulates the data in a corresponding manner, and converts the complex symbols into phase and magnitude symbols. The OFDM modulator 217 receives the time domain signal and performs an Inverse Fast Fourier Transform (IFFT) operation to convert the signal into a frequency domain signal. The DAC 219 receives a digital signal and converts it into an analog signal.

The RF processor 221 converts the baseband signal into an RF band signal. In particular, according to the present invention, the signal is converted into the corresponding RF band signal determined by the frequency determiner 227.

The power amplifier 223 amplifies the power of the transmission signal for smooth reception of the signal at the receiver. In particular, according to the present invention, the power of the transmission signal is amplified by the determination of the transmission power determination unit 225.

The frequency determiner 225 selects an operating frequency band using a signal received from an adjacent base station. In other words, the frequency determiner 225 measures the strength of signals received for each frequency band from adjacent base stations in the scan mode. Then, the frequency band with the smallest received signal strength is selected.

The transmission power determiner 227 determines the transmit power in the frequency band determined by the frequency determiner 225. In other words, the transmission power determiner 225 receives the received signal strength of the neighboring base station received from the frequency determiner 225 in the corresponding frequency band, decodes the control signal received from the neighboring base station, and thus the neighboring base station. Check the transmit power. Thereafter, path loss is confirmed using the checked transmission power and the received signal strength, and the transmission power for the frequency band is determined based on the path loss. Here, when the signal of the neighboring base station is weak enough that decoding is impossible, the transmission power for the frequency band is determined as the maximum power available.

3 is a flowchart illustrating a procedure for determining an operating frequency band and signal strength by a base station in a broadband wireless communication system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, in step 301, the base station converts a transmission section into a reception section. That is, in order to receive a signal from an adjacent base station, the TDD mode is operated in reverse to switch to the scan mode.

After the transmission section is switched to the reception section, the base station proceeds to step 303 and checks whether signals from neighboring base stations are received.

When the signals of the neighbor base stations are received, the base station proceeds to step 305 to classify the signals received from the neighbor base stations by frequency band and measure the received signal strength.

After measuring the received signal strength for each frequency band, the base station proceeds to step 307 to select the frequency band with the lowest received signal strength for use in communication.

In step 309, the base station determines whether the signal of the selected frequency band is decodable. In other words, it is checked whether the received signal from the neighboring base station using the selected frequency band is strong enough to decode.

If the received signal strength from the neighboring base station is weak and cannot be decoded, the base station proceeds to step 311 to determine the transmit power at the maximum power available. That is, since the signal from the neighboring base station is weak, the interference from the neighboring base station is insignificant, which is the basis for the determination that the interference to the neighboring base station will be insignificant even using the maximum power. Thus, the base station determines the transmit power at the maximum power available.

On the other hand, if the signal strength of the neighboring base station is strong enough to decode, the base station proceeds to step 315 to decode the control signal of the neighboring base station, and then the transmit power of the neighboring base station and the received signal strength of the selected frequency band To measure path loss.

In step 315, the base station determines transmission power based on a path loss with the neighbor base station. That is, when the transmission power of a specific strength is used, the signal strength to be received by the neighboring base station is predicted with reference to the path loss, and the transmission power is determined so that the received signal strength to the neighboring base station does not act as interference. do.

In step 317, the base station performs communication with the determined frequency band and transmission power.

The embodiment described with reference to FIG. 3 described a procedure in which a base station determines itself an operating frequency band and a transmission power in a broadband wireless communication system. The base station may determine the operating frequency band and the transmission power of the minimum interference by performing the above-described procedure. In addition, since each base station sequentially performs the above-described operating procedure, it is possible to optimize the frequency band allocation and the transmission power of each cell in the entire communication system.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible 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.

As described above, in the broadband wireless communication system, the base station determines the operating frequency band and the transmission power based on the received signal from the adjacent base station, thereby optimizing the frequency allocation and the transmission power of the communication system without additional equipment.

Claims (14)

A base station apparatus of a broadband wireless communication system, A transmit / receive switch that reverses a transmit / receive mode to receive signals of neighboring base stations; A frequency selector for selecting an operating frequency band by referring to signals received from the neighbor base stations; And a transmission power determiner for determining signal transmission power in the operating frequency band. The method of claim 1, The transmission and reception switch, Apparatus characterized in that the time division duplex (TDD: time division duplex) transmission and reception switch. The method of claim 1, The frequency selector, And selecting a frequency band having the lowest received signal strength among available frequency bands. The method of claim 1, The transmission power determiner, And calculating a path loss with an adjacent base station using the selected operating frequency band and determining transmission power with reference to the path loss. The method of claim 4, wherein The transmission power determiner, Decoding the control information of the neighboring base station using the selected operating frequency band to confirm the transmission power of the neighboring base station, and calculates the path loss using the received signal strength from the neighboring base station and the identified transmission power. Device. The method of claim 1, The transmission power determiner, And when the received signal strength of the selected operating frequency band is lower than a predetermined reference value, determining the transmission power at the maximum power available. The method of claim 6, And the predetermined reference value is a minimum decodable signal strength value. A method for selecting an operating frequency band at a base station of a broadband wireless communication system, Receiving the signals of adjacent base stations by switching the transmission / reception mode to the reverse; Selecting an operating frequency band according to the received signal strength from the adjacent base stations; And determining transmission power using the received signal strength in the operating frequency band. The method of claim 8, The transmission and reception mode, A time division duplex (TDD: Time Division Duplex) method characterized in that divided into time intervals. The method of claim 8, The process of selecting the operating frequency band, Measuring reception strength by dividing the signals from the adjacent base stations according to available frequency bands; And selecting a frequency band having the lowest received signal strength. The method of claim 8, The process of determining the transmission power, Calculating a path loss with an adjacent base station using the selected frequency band; Determining transmission power with reference to the path loss. The method of claim 11, The process of measuring the path loss, Confirming transmission power of the neighboring base station by decoding a control signal of the neighboring base station using the selected frequency band; And measuring a path loss using the transmit power of the neighboring base station and the received signal strength in the selected frequency band. The method of claim 8, The process of determining the transmission power, Checking whether the received signal strength in the selected frequency band is equal to or less than a predetermined reference value; Determining the transmit power with the maximum power available. The method of claim 13, And the predetermined reference value is a minimum decodable signal strength value.

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