WO2009093810A1

WO2009093810A1 - Transmitter and method for subcarrier scaling in mobile station of ofdma

Info

Publication number: WO2009093810A1
Application number: PCT/KR2008/007613
Authority: WO
Inventors: Dong-Kyu Kim
Original assignee: Posdata Co Ltd
Current assignee: Posdata Co Ltd
Priority date: 2007-12-28
Filing date: 2008-12-23
Publication date: 2009-07-30
Anticipated expiration: 2010-06-28
Also published as: KR100902017B1

Abstract

A transmitter for subcarrier scaling in a SS of Orthogonal Frequency Division Multiplexing Access (OFDMA) includes a modem calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, calculating a correction control value according to the scaling control value, adjusting the subcarriers allocated to the transmission signal according to the scaling control value, and outputting the transmission signal to which the adjusted subcarriers are allocated, and a Radio Frequency (RF) unit adjusting power of the transmission signal by the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.

Description

TRANSMITTER AND METHOD FOR SUBCARRIER SCALING IN MOBILE STATION OF OFDMA

Technical Field

[1] The present invention relates to transmission and reception of data in a mobile station of Orthogonal Frequency Division Multiplexing Access (OFDMA), and more particularly, to a transmitter and method which can adjust subcarriers used in a transmission unit of a modem according to the number of subcarriers allocated from a base station for transmission of uplink data. Background Art

[2] In communication environments of OFDMA, a base station generally transmits the allocation information of subcarriers for the transmission of uplink data to each subscriber station (hereinafter, referred to as "SS") by using downlink data. Accordingly, the SS receiving the downlink data checks the allocation information of the received downlink data, and allocates subcarriers as many as subcarriers allocated thereto and transmits the uplink data. FIG. 1 illustrates the configuration of a general transmitter/receiver in an OFDMA SS for the transmission/reception of data.

[3] Referring to FIG. 1, the transmitter/receiver in the SS includes a modem processing a digital signal, and a Radio Frequency (RF) unit 10 processing an analog signal.

[4] The modem includes a transmission unit 20 of OFDM communication system for processing the digital signal, a reception unit 30 of OFDM communication system for processing the digital signal, a subcarrier processing unit 41 processing data to be carried in a subcarrier allocated from a base station, a subcarrier processing unit 42 processing received data, and a frequency domain processing unit 50. Since the transmission unit 20 and the reception unit 30 are well known, their detailed description will be omitted.

[5] The RF unit 10 includes a power amplifier amplifying a transmission signal, and controls the power amplifier according to a control value (P ). Herein, the control value (P ) is a transmission power value indicated by the base station.

Tx _ Amp

[6] In the OFDMA SS having such a configuration, the number of subcarriers allocated from the base station for the transmission of uplink data is very variable. The OFDMA SS generates a standardized transmission signal irrespective of the number of the subcarriers and transmits it to the base station. For example, if the magnitude of Fast Fourier Transform (FFT) used for OFDM modulation is 1024, the number of subcarriers which the base station can allocate to each SS is 1 to 1024. When the 840 subcarriers and the 24 subcarriers among the 1024 subcarriers are allocated, the output signals of the SS are seen as FIGS. 2 and 3. The output signals seen in FIGS. 2 and 3 are an in-phase signal or a quadrature signal among FFT outputs.

[7] As shown in FIG. 2, a signal using the 840 subcarriers is distributed in the entire input/output section of a digital-to-analog controller (DAC). However, as shown in FIG. 3, it can be seen that a signal using the 24 subcarriers is distributed only in approximately a sixth of the input/output section of the DAC when it is transmitted as it is without being adjusted. When the size of used DAC bits is 10, only about 7.5 bits among the 10 bits of the DAC are used and the remaining about 2.5 bits are not used when a signal to which the 24 subcarriers are allocated is transmitted, and thus the DAC cannot be utilized to the utmost. Disclosure of Invention Technical Problem

[8] An aspect of the present invention provides a transmitter and method which can adjust subcarriers according to the number of allocated subcarriers in order to use the entire bit of a digital-to-analog controller (DAC) even when the number of the subscribers, which are allocated to a SS from a base station for the transmission of uplink data, is small in Orthogonal Frequency Division Multiplexing Access (OFDMA) communication environments. Technical Solution

[9] According to an aspect of the present invention, there is provided a transmitter for subcarrier scaling in a SS of Orthogonal Frequency Division Multiplexing Access (OFDMA), including: a modem calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, calculating a correction control value according to the scaling control value, adjusting the subcarriers allocated to the transmission signal according to the scaling control value, and outputting the transmission signal to which the adjusted subcarriers are allocated; and a Radio Frequency (RF) unit adjusting power of the transmission signal by the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.

[10] According to another aspect of the present invention, there is provided a transmitter for subcarrier scaling in a SS of OFDMA, including: a control unit calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, and calculating a correction control value according to the scaling control value; a scaling unit adjusting the subcarriers allocated to the transmission signal according to the scaling control value; a transmission unit performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; and a RF unit adjusting power of the transmission signal output from the transmission unit by the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.

[11] According to another aspect of the present invention, there is provided a method for subcarrier scaling in a SS of OFDMA, including: allocating subcarriers to a transmission signal according to a searched maximum number of subcarriers by using allocation information transmitted from a base station; calculating a scaling control value of the subcarriers according to the searched maximum number of the subcarriers, and calculating a correction control value according to the scaling control value; adjusting the subcarriers allocated to the transmission signal according to the scaling control value; performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; adjusting power of the transmission signal by the correction control value; and amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to the base station.

[12]

Advantageous Effects

[13] Embodiments of the present invention can increase power of a transmission signal, i.e., amplitude of the transmission signal, by subcarrier scaling in a modem being a digital module in a transmitter of an Orthogonal Frequency Division Multiplexing Access (OFDMA) SS, and thus can decrease the power amplification of a Radio Frequency (RF) unit being an analog module. Accordingly, when subcarriers less than the total number of available subcarriers are used, embodiments of the present invention can solve the limitation that the amplitude of an up-link signal is relatively reduced, and can save the consumption power of the analog module occupying a considerable amount of consumption power. Brief Description of Drawings

[14] The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[15] FIG. 1 illustrates the configuration of a general transmitter/receiver in an OFDMA

SS;

[16] FIGS. 2 and 3 are characteristic diagrams of signals generated in a time domain processing unit according to the number of allocated subcarriers in a general SS;

[17] FIG. 4 is a block diagram of a transmitter/receiver in an OFDMA SS according to an embodiment of the present invention;

[18] FIG. 5 is a flowchart illustrating a method for subcarrier scaling in the OFDMA SS according to an embodiment of the present invention;

[19] FIG. 6 is a flowchart illustrating the operation of the control unit of the transmitter according to an embodiment of the present invention;

[20] FIGS. 7 and 8 are characteristic diagrams illustrating the output characteristics of the fast fourier transformer of the receiver when scaling is not performed on a signal using subcarriers; and

[21] FIG. 9 is a characteristic diagram illustrating the output characteristics of the fast fourier transformer of the receiver when scaling is performed on a signal using subcarriers according to an embodiment of the present invention.

[22]

Best Mode for Carrying out the Invention

[23] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, when the detail description of the relevant known function or configuration is determined to unnecessarily obscure the important point of the present invention, the detail description will be omitted.

[24] In embodiments of the present invention, the following description will be made by applying a SS in Orthogonal Frequency Division Multiplexing Access (OFDMA) communication environments. The number of subcarriers is allocated to the SS from a base station, and the SS includes a transmitter of a novel configuration which has a subcarrier scaling function added to a general transmission unit for adjusting each subcarrier according to the number of allocated subcarriers. In embodiments of the present invention, the following description will be focused on the transmitter of the novel configuration. Furthermore, the receiver of the SS is not included in the scope of the present invention, but summary description thereof will be made by applying a general receiver of OFDMA for convenience of the description of the transmitter.

[25] Hereinafter, the configuration of a transmitter/receiver in a SS according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[26] FIG. 4 is a block diagram of a transmitter/receiver in an OFDMA SS according to an embodiment of the present invention.

[27] Referring to FIG. 4, the transmitter/receiver may greatly be divided into a modem and a Radio Frequency (RF) unit 110.

[28] The modem includes a frequency domain processing unit 120, a control unit 130, subcarrier allocating units 140a and 140b, a scaling unit 150, a transmission unit 160, and a reception unit 170. Herein, the control unit 130 is included in the modem and performs an overall control. Alternatively, the control unit 130 can be configured in the outside of the modem and can control the modem overall.

[29] The RF unit 110 includes a power amplifier, and adjusts the power of a transmission signal output from the modem to a low level and amplifies the adjusted power according to a correction control value received from the control unit 130. That is, the RF unit 110 decreases the power of the transmission signal by a power level of subcarriers increased by the scaling unit 150, and amplifies the transmission signal.

[30] The control unit 130 searches the number of subcarriers to be transmitted per each

OFDMA symbol within a transmission time allocated to a SS on the basis of the allocation information of subcarriers transmitted from a base station, searches the maximum number of subcarriers to be allocated to the transmission signal, and thereafter transmits relevant allocation information to the subcarrier allocating unit 140a to allocate subcarriers as many as the searched maximum number of the subcarriers to the signal. The control unit 130 calculates a scaling control value according to the number of subcarriers to be allocated to the transmission signal by using a predetermined look-up table, and calculates the correction control value in accordance with to the scaling control value to thereby transfer it to the RF unit 110. Herein, the correction control value is a value for controlling the power amplification of the transmission signal, and a specific calculation method thereof will be described below. The scaling control value may be a multiplication value multiplied by the complex number of the subcarriers, or may be a shift value for shifting the each subcarrier by a bit unit.

[31] In the transmitter, the subcarrier allocating unit 140a allocates subcarriers to the transmission signal according to the allocation information transmitted from the control unit 130, that is, the number of the searched maximum number of the subcarriers. In the receiver, the subcarrier allocating unit 140b allocates subcarriers to a reception signal.

[32] The scaling unit 150 is configured between the subcarrier allocating unit 140a and the transmission unit 160. The scaling unit 150 receives the scaling control value from the control unit 130 and adjusts subcarriers allocated by the subcarrier allocating unit 140a according to the received scaling control value, thereby increasing the power of the transmission signal. When the scaling unit 150 receives a multiplication value as the scaling control value and uses a multiplication scheme, the scaling unit 150 can be configured with a multiplier. When the scaling unit 150 receives a shift value as the scaling control value and uses a shift scheme, the scaling unit 150 can be configured with a shifter. The multiplication scheme and the shift scheme will be described below in detail.

[33] The transmission unit 160 includes an inverse fast fourier transformer (IFFT) 161, a parallel-to-serial converter (P/S) 162, a Cyclic Prefix (CP) adder 163, a time domain processing unit 164, and a digital-to- analog converter (DAC) 165. The transmission unit 160 performs a digital signal processing on a signal output from the scaling unit 150 and converts a digital signal into an analog signal, and thereafter transmits the converted analog transmission signal to the RF unit 110.

[34] The reception unit 170 includes a Fast Fourier Transformer (FFT) 171, a serial- to-parallel converter (S/P) 172, a Cyclic Prefix (CP) remover 173, a time domain processing unit 174, and an analog-to-digital converter (ADC) 175. The reception unit 170 performs a digital signal processing on a signal transmitted from the RF unit 110 and transmits a digital reception signal to the subcarrier allocating unit 140b.

[35] In the transmitter/receiver of the OFDMA SS having such a configuration, it is required to calculate the scaling control value for the number of used subcarriers as listed in the following Table 1 in order to adjust the transmission signal and transmit the adjusted signal to the base station. The following Table 1 represents a case, in which the subcarriers are used by multiples of 24, as an example. The following Table 1 represents the calculated values of the total power of an OFDMA symbol on the each multiple of 24. Specifically, when the symbol power is compared with the total power of the OFDMA symbol using the number of subcarriers capable of being allocated to the utmost, the following Table 1 represents the difference between the symbol power and the total power of the OFDMA symbol.

[36] Table 1 [Table 1]

[37] As shown in the above Table 1, an OFDMA power using 24 subcarriers is reduced by -15.44[dB] relative to an OFDMA power using 840 subcarriers. Accordingly, a transmission signal is also reduced. Consequently, when the scaling control value (optimal scaling value) is increased by approximately 5.9 times, a signal power is increased to use the entire bit of the digital-to- analog converter 165.

[38] In the above Table 1, the number (No subca) of the subcarriers of the first column and a multiplication value (optimal scaling value) which is the scaling control value of the fourth column or a shift value (approximated scaling value) which is the scaling control value of the firth column may be preset in the look-up table, wherein the shift value (approximated scaling value) is the scaling control value of when a shift is performed by a bit unit. In this way, the control unit 130 can know a scaling power value and a relative difference value in accord with the scaling in the modem by using the preset values.

[39] When the first column and the fourth column are used as the look-up table in the above Table 1, a scheme of multiplying the scaling control value can be applied.

[40] For example, when the output of the subcarrier allocating unit 140a is "X =X +X

K K, I K, Q scaling control value is "a" which is a multiplication value, the control unit 130 performs scaling by multiplying a real part and an imaginary part by a as expressed in Equation (1) below. [41] X K , adj =aX k ,i +jaX K ,Q (1)

[42] where K is a subcarrier index, X K ,1 is the value of the real part (or In-phase) of a complex value (X K ), and X K ,Q is the value of the imaginary part (or Quadrature) of the complex value (X ). [43] When the first column and the fifth column are used as the look-up table in the above

Table 1, a scheme of shifting by a bit unit can be applied. Such a scheme can obtain a result such as the multiplication of the index number of 2. [44] The following Table 2 represents the increased power of when a left shift is performed by 1 to 3 bits, and it can be seen from the following Table 2 that the increased power is approximately a multiple of 6[dB]. Accordingly, scaling can simply be approximated by the left shift as expressed in Equation (2) below. [45] Table 2

[Table 2]

[Table ]

[46]

[47] X K,adj =(X K,I «b)+j(X K,Q «b) (2) [48] where A«b means a bit-shift operation that shifts a complex value (A) to the left by a shift value (b bit). Accordingly, the control unit 130 respectively shifts the complex value (X , X ) of the output of the subcarrier allocating unit 140a by b and adjusts the power of a signal.

[49] Then, the following description will be made in detail with reference to the accompanying drawings on a method for scaling of the transmission signal by using the multiplication or shift scheme.

[50] FIG. 5 is a flowchart illustrating a method for scaling in the OFDMA SS according to an embodiment of the present invention.

[51] Referring to FIG. 5, in operation 210, the SS searches the maximum number of subcarriers by using allocation information transmitted from the base station, and allocates the subcarriers to the transmission signal according to the searched maximum number of the subcarriers by the subcarrier allocating unit 140a.

[52] In operation 220, the SS calculates the scaling control value of the subcarriers according to the searched maximum number of the subcarriers by the control unit 130 and calculates the correction control value in accordance with the scaling control value. The calculations on the scaling control value and the correction control value will be described below in detail.

[53] Subsequently, in operation 230, the SS performs scaling for the subcarriers allocated to the transmission signal according to the calculated scaling control value by the scaling unit 150, and thereafter transmits the signal, to which the adjusted subcarriers are allocated, to the transmission unit 160.

[54] Accordingly, in operation 240, the SS performs a digital signal processing on the signal transmitted from the scaling unit 150 to output an analog transmission signal. That is, the transmission unit 160 performs Inverse Fast Fourier Transform (IFFT) on the signal by the inverse fast fourier transformer 161, and converts the transformed signal into a serial signal by the parallel-to-serial converter 162. Subsequently, the transmission unit 160 adds a Cyclic Prefix (CP) to the converted serial signal by the CP adder 163, converts it into the time domain by the time domain processing unit 164, converts the converted signal into an analog signal, and transmits the converted analog signal as a transmission signal to the RF unit 110.

[55] In operation 250, the RF unit 110 of the SS receives the analog transmission signal from the transmission unit 160, and reduces the power of the transmission signal by the correction control value transmitted from the control unit 130.

[56] In operation 260, the SS amplifies the transmission signal to the adjusted power level by the RF unit 110 and transmits the amplified signal to the base station. At this point, the power of the transmission signal output from the antenna of the RF unit 110 must be in accordance with a numerical value indicated by the base station irrespective of scaling. That is, in a case of the transmission signal, since the power increased by the modem is again reduced according to the correction control value output from the RF unit 110, it can be seen that the power of the transmission signal is in accordance with the numerical value indicated by the base station.

[57] The following description will be made in detail with reference to the accompany drawings on the operation of the control unit of the transmitter which calculates the scaling control value and the correction control value in the method for scaling for the subcarrier.

[58] FIG. 6 is a flowchart illustrating the operation of the control unit of the transmitter according to an embodiment of the present invention.

[59] Referring to FIG. 6, in operation 310, the control unit 130 of the transmitter of the SS receives subcarrier allocation information from the base station. In operation 320, the control unit 130 searches the maximum number of the subcarriers on the basis of the subcarrier allocation information, and transmits allocation information associated with the searched maximum number of the subcarriers to the subcarrier allocating unit 140a.

[60] In operation 330, the control unit 130 calculates the scaling control value by using the predetermined look-up table, calculates the correction control value for controlling the power amplifier (not shown) of the RF unit 110, and transfers the scaling control value and the correction control value to the RF unit 110. Herein, the scaling control value may be calculated using the multiplication or shift scheme, and consequently the values of the above Table 1 can be obtained. Moreover, the correction control value may be calculated by using Equation (3) below.

[61] P Tx _ Amp , adj =P Tx _ Amp -P s (3)

[62] where P is a control value for controlling the power amplifier when the

Tx _ Amp subcarriers are not adjusted, P is a control value, i.e., the correction control

Tx _ Amp , adj value for controlling the power amplifier when the subcarriers are adjusted, P is obtained by multiplying a value corresponding to the third column of the above Table 1 by - 1 when the multiplication scheme is applied, and P is a value corresponding to the sixth column of the above Table 1 when the shift scheme is applied. For example, when 24 subcarriers are used, since a signal 15.44[dB] less than that of when 840 subcarriers are used is generated, the modem increases the levels of the in-phase signal and quadrature signal of each of the 24 subcarriers by 5.9 times. This means that the modem amplifies the transmission signal by 15.44[dB], and thus the amplification degree of the Radio Frequency (RF) is reduced by 15.44[dB]. Accordingly, the correction control value (P Tx _ Amp , adj ) is "P Tx _ Amp -15.44[dB]".

[63] In operation 340, the control unit 130 transmits the calculated scaling control value to the scaling unit 150. Therefore, the scaling unit 150 applies the scaling control value to the complex value of the subcarriers output from the subcarrier allocating unit 140a and increases the level of the subcarriers by the scaling control value.

[64] In operation 350, the control unit 130 transfers the calculated correction control value to the RF unit 110. Accordingly, the RF unit 110 amplifies the output analog signal, i.e, the transmission signal and transmits the amplified signal to the base station. At this point, the RF unit 110 amplifies the power of the transmission signal by the correction control value transmitted from the control unit 130.

[65] When the subcarriers of the signal to be transmitted to the base station are adjusted and transmitted by the above-described processes, the output of the fast fourier transformer of the receiver is seen as FIG. 9. This is the same as FIG. 8, and is identical to when scaling is not performed as seen in FIGS. 7 and 8. More accurately, when scaling is performed, the quality of a signal is improved when a small number of subcarrier is used, but the influence is very small in general wireless communication environments when a signal to noise ratio (SNR) is 35 [dB] or less. This is because a noise power is relatively higher than an improved value. FIGS. 7 and 8 are characteristic diagrams illustrating the output characteristics of the fast fourier transformer of the receiver when a 10-bit DAC conversion is performed on the respective signals using 840 subcarriers and 24 subcarriers and the converted signals are transmitted.

[66] While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the spirit and scope of the present invention should not be limited to the above-described embodiments, and embodiments of the present invention are defined by the following claims, with equivalents of the claims to be included therein.

Claims

[1] A transmitter for subcarrier scaling in a subscriber station of Orthogonal

Frequency Division Multiplexing Access (OFDMA), comprising: a modem calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, calculating a correction control value according to the scaling control value, adjusting the subcarriers allocated to the transmission signal according to the scaling control value, and outputting the transmission signal to which the adjusted subcarriers are allocated; and a Radio Frequency (RF) unit adjusting power of the transmission signal by using the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.

[2] The transmitter of claim 1, wherein the modem searches the maximum number of subcarriers by using allocation information transmitted from the base station, allocates subcarriers to the transmission signal by the searched maximum number of the subcarriers, and calculates the scaling control value by using a predetermined look-up table.

[3] The transmitter of claim 2, wherein the modem calculates the scaling control value to use entire bit when the transmission signal is digital-to-analog converted, and adjusts the allocated subcarriers according to the scaling control value to increase power of the transmission signal.

[4] The transmitter of claim 2, wherein the modem uses the scaling control value as a multiplication value, and multiplies a real part and imaginary part of a complex value of the allocated subcarriers by the multiplication value to adjust the subcarriers.

[5] The transmitter of claim 2, wherein the modem uses the scaling control value as a shift value of a bit unit, and shifts a complex value of the allocated subcarriers by the shift value to adjust the subcarriers.

[6] A transmitter for subcarrier scaling in a subscriber station of Orthogonal

Frequency Division Multiplexing Access (OFDMA), comprising: a control unit calculating a scaling control value of subcarriers according to the number of subcarriers to be allocated to a transmission signal, and calculating a correction control value according to the scaling control value; a scaling unit adjusting the subcarriers allocated to the transmission signal according to the scaling control value; a transmission unit performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; and a Radio Frequency (RF) unit adjusting power of the transmission signal output from the transmission unit by using the correction control value, amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to a base station.

[7] The transmitter of claim 6, further comprising a subcarrier allocating unit allocating subcarriers to the transmission signal by a searched maximum number of subcarriers when the control unit has searched the maximum number of the subcarriers by using allocation information transmitted from the base station.

[8] The transmitter of claim 6, wherein the scaling unit adjusts the subcarriers by the scaling control value to increase power of the signal to which the subcarriers are allocated in order to use entire bit upon digital-to-analog conversion.

[9] The transmitter of claim 6, wherein the scaling unit is a multiplier which receives a multiplication value as the scaling control value from the control unit, and multiplies a real part and imaginary part of a complex value of the allocated subcarriers by the multiplication value to adjust the subcarriers.

[10] The transmitter of claim 6, wherein the scaling unit is a shifter which receives a shift value of a bit unit as the scaling control value, and shifts a complex value of the allocated subcarriers by using the shift value to adjust the subcarriers.

[11] The transmitter of claim 1 or 6, wherein the correction control value is obtained by subtracting a power value, which is increased according to the subcarrier scaling, from a control value for controlling a power amplification of the transmission signal.

[12] A method for subcarrier scaling in a subscriber station of Orthogonal Frequency

Division Multiplexing Access (OFDMA), comprising: allocating subcarriers to a transmission signal according to a searched maximum number of subcarriers by using allocation information transmitted from a base station; calculating a scaling control value of the subcarriers according to the searched maximum number of the subcarriers, and calculating a correction control value according to the scaling control value; adjusting the subcarriers allocated to the transmission signal according to the scaling control value; performing a digital signal processing on a signal to which the adjusted subcarriers are allocated, and outputting an analog transmission signal; adjusting power of the transmission signal by the correction control value; and amplifying the transmission signal to the adjusted power level, and transmitting the amplified signal to the base station.

[13] The method of claim 12, wherein the scaling control value is calculated by using a predetermined look-up table and is a multiplication value to be multiplied by a real part and imaginary part of a complex value of the allocated subcarriers.

[14] The method of claim 12, wherein the scaling control value is calculated by using a predetermined look-up table and is a shift value for shifting a complex value of the allocated subcarriers by a bit unit.

[15] The method of claim 12, wherein the correction control value is obtained by subtracting a power value, which is increased according to the subcarrier adjusting, from a control value for controlling a power amplification of the transmission signal.

[16] The method of claim 12, wherein the ajusting of the subcarriers comprises: receiving a multiplication value as the scaling control value; and multiplying a real part and imaginary part of a complex value of the allocated subcarriers by using the received multiplication value to adjust the subcarriers.

[17] The method of claim 12, wherein the scaling of the subcarriers comprises: receiving a shift value of a bit unit as the scaling control value; and shifting the allocated subcarriers by using the received shift value to adjust the subcarriers.