Patent Publication Number: US-2016227549-A1

Title: Radio device that has function to reduce peak power of multiplexed signal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-020112, filed on Feb. 4, 2015, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein are related to a radio device that has a function to reduce a peak power of a multiplexed signal. 
     BACKGROUND 
     In radio communication systems, it is often desirable that transmission signals are linearly amplified without distortion. However, the input/output characteristics of the power amplifier that amplifies a transmission signal, that is, the relationship between the input power and the output power becomes non-linear from linear as the input power increases, and the output power saturates when the input power exceeds a certain power. 
     In recent radio communication systems, signals transmitted from a radio base station are multi-carrier signals in which a plurality of carrier signals are multiplexed, for example. Examples of respective carrier signals multiplexed in the multi-carrier signal include a Wideband Code Division Multiple Access (WCDMA) signal and an Orthogonal Frequency Division Multiplexing (OFDM) signal. These multi-carrier signals in which a plurality of signals are multiplexed have a larger Peak to Average Power Ratio (PAPR) compared to that of single-carrier signals. If a power amplifier with a high saturation output power and a large backoff adapted for the peak power is used for linear amplification of a signal having a large PAPR, the consumption power of the device including such a power amplifier becomes large, which leads to a larger size of the device. Therefore, a process for reducing the peak power of the signal by clipping or the like is performed in order to reduce the PAPR of the signal. Such techniques for reducing the peak power of the signal are called Crest Factor Reduction (CFR). 
     Meanwhile, a device described below that performs peak suppression in accordance with a input limit power for a power amplifier has been known. That is, the device is configured to include a power correction value generator and an output power error corrector. Based on the carrier allocation and the peak suppression setting related to either one or both of the number of carrier signals and the frequency arrangement, the power correction value generator obtains a power correction value for minimizing the error in a carrier multiplexed signal with respect to the reference output power value caused by peak power suppression under the corresponding carrier setting. The output power corrector corrects the signal gain before or after the multiplexing of the carrier signals using the power correction value obtained by the power correction value generator. 
     Meanwhile, a transmitting device described below that transmits OFDM signals has been known. That is, generating means generate a plurality of OFDM signals. Peak suppression means for base band (BB) performs peak suppression for each of the OFDM signals, according to the plurality of OFDM signals generated by the generating means. IF converting means converts the respective OFDM signals for which peak suppression has been performed by the base band peak suppressing means into signals of intermediate frequency (IF frequency). Intermediate frequency peak suppressing means performs peak suppression for each of the signals of intermediate frequency, according to the respective signals of intermediate frequency converted by the IF converting means. Combining means combines the plurality of signals of intermediate frequency for which peak suppression has been performed by the intermediate frequency peak suppressing means. Amplifying means amplifies the output signal from the combining means. The base band peak suppressing means performs the peak suppression using a combined value of the absolute values of the respective OFDM signals as a predicted peak value. In addition, the intermediate frequency peak suppression means performs peak suppression using the absolute value of the combined plurality of signals of intermediate frequency as a predictive peak value. 
     In addition, a peak suppressor described below that separates a complex transmission signal into a real part signal and an imaginary part signal and performs a peak suppression process for the real part signal with respect to the signal after separation has been known. That is, the peak suppressor is equipped with a sample unit that selects samples corresponding to a prescribed number of samples from the signal after separation and a suppression signal calculator that calculates a peak suppression signal using the selected samples, and the peak suppressor obtains the signal after the peak suppression process according to the peak suppression signal and the signals after separation. 
     A transmitter described below has been known. That is, baseband limiter means performs a peak reduction process in the base band with respect to digital signals of a plurality of transmitting carriers. Band limiting filter means performs a band limiting process for the digital signals of the respective carriers for which the peak reduction process has been performed. Orthogonal modulation processing means performs an orthogonal modulation process for the digital signals of the respective carriers for which the band limiting process has been performed. Adding means adds the digital signals of the respective carriers for which the orthogonal modulation process has been performed. Intermediate frequency limiter means multiplies the resultant signal of the addition by a window function that is weighted according to the magnitude of the detected peak and performs a peak reduction process. At this time, when a plurality of peak reduction processes overlap, the weighting for later window function is reduced in order to prevent excessive suppression. 
     Related arts are described in Japanese Laid-open Patent Publication No. 2006-67073, Japanese Laid-open Patent Publication No. 2008-294519, Japanese Laid-open Patent Publication No. 2009-100218, International Publication Pamphlet No. WO 2006/049140. 
     SUMMARY 
     According to an aspect of the embodiments, a radio device includes: a peak power reducer that reduces, according to a peak power of a multi-carrier signal obtained by a multiplexing of a plurality of carrier signals, a gain of the carrier signals before the multiplexing; and an output power corrector that corrects a power of the carrier signals before the multiplexing using a power correction value according to an occupied bandwidth of the multi-carrier signal. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A-1C  illustrate an example of a radio device according to the first embodiment; 
         FIG. 2  illustrates an example of a peak reduction value calculator; 
         FIG. 3  illustrates an example of a power correction value table according to the first embodiment; 
         FIG. 4A  illustrates an example of a multi-carrier signal having a narrow occupied bandwidth to which a peak power suppression process has not been applied; 
         FIG. 4B  illustrates an example of a multi-carrier signal having a broad occupied bandwidth to which a peak power suppression process has not been applied; 
         FIG. 5  illustrates an example of changes with time in the power of multi-carrier signals; 
         FIG. 6A  illustrates an example of a multi-carrier signal having a narrow occupied bandwidth to which a peak power suppression process has been applied; 
         FIG. 6B  illustrates an example of a multi-carrier signal having a broad occupied bandwidth to which a peak power suppression process has been applied; 
         FIG. 7  is a flowchart illustrating an example of a transmission process for a multi-carrier signal performed by a radio device according to the first embodiment; 
         FIG. 8  is an exemplary hardware configuration diagram for a radio device according to the first embodiment; 
         FIGS. 9A-9B  illustrate an example of a radio device according to the second embodiment; 
         FIG. 10  illustrates an example of a power correction value table according to the second embodiment; 
         FIG. 11  is a flowchart illustrating an example of a transmission process for a multi-carrier signal performed by a radio device according to the second embodiment; 
         FIGS. 12A-12B  illustrate an example of a radio device according to the third embodiment; 
         FIG. 13  is a flowchart illustrating an example of a transmission process for a multi-carrier signal performed by a radio device according to the third embodiment; 
         FIGS. 14A-14B  illustrate an example of a radio device according to the fourth embodiment; and 
         FIG. 15  is a flowchart illustrating an example of a transmission process for a multi-carrier signal performed by a radio device according to the fourth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the invention are described with reference to the drawings. 
     First Embodiment 
       FIGS. 1A-1C  are exemplary diagrams for a radio device according to the first embodiment. A radio device  100  according to the first embodiment illustrated in  FIGS. 1A-1C  may be a part of a radio base station such as evolved Node B (eNodeB) standardized in the specifications of Third Generation Partnership Project (3GPP), for example. In addition, the radio device  100  may be a device called Radio Equipment (RE) or Remote Radio Head (RRH), for example. 
     As illustrated in  FIGS. 1A-1C , the radio device  100  includes a control processor  110 , N signal processors  120  ( 120 - 1  through  120 -N), a peak reduction value calculator  130 , a combiner  140 , a distortion compensator  150 , a Digital to Analog Converter (DAC)  160 , a radio frequency converter  170 , a power amplifier  180 , and an antenna  190 . Here, the symbol “N” represents an integer that is 2 or greater and that corresponds to the number of carriers in the multi-carrier signal transmitted from the radio device  100 . Meanwhile, when the N identical elements are not to be particularly distinguished in the explanations below, the indication is omitted after the hyphen attached to the reference numerals for the purpose of distinction between the N identical elements. For example, when the signal processors  120 - 1  through  120 -N are not to be particularly distinguished, each of them is described as the signal processor  120 . 
     Each of the signal processors  120 - 1  through  120 -N processes one carrier signal that is different from each other in the N carrier signals to be combined (multiplexed) in the multi-carrier signal. The signal processor  120  generates a corresponding carrier signal according to the instruction from the control processor  110 . Specifically, the signal processor  120  performs signal processing for a baseband signal before it is put onto a carrier according to the instruction from the control processor  110 , and generate a carrier signal. Meanwhile, in the explanations below, the “baseband signal before it is put onto a carrier” may be referred to as “the baseband signal of a carrier”. 
     The baseband signals # 1  through #N that are respectively processed by the signal processors  120 - 1  through  120 -N are given from an application (not illustrated in the drawing). The application that gives the baseband signals to the signal processors  120  may be a part of the radio base station. In addition, the application may be a device called Radio Equipment Control (REC) or Base Band Unit (BBU), for example. 
     Baseband signals given from the application to the signal processors  120  may be signals in which complex modulation is applied to a data signal according to a prescribed Radio Access Technology (RAT) with respect to the In-phase component and the Quadrature component. The prescribed radio access technology may be WCDMA, Long Term Evolution (LTE), and LTE-Advanced (LTE-A), or the like. For example, in WCDMA, baseband signals given to the signal processor  120  are WCDMA signals in which a data signal is modulated according to modulation formats such as Quadrature Phase Shift Keying (QPSK) and 16 Quadrature Amplitude Modulation (16QAM) or the like. Meanwhile, in LTE and LTE-A, baseband signals given to the signal processors  120  are OFDM signals in which a data signal is modulated according to modulation formats such as QPSK, 16QAM, and 64QAM or the like for each subcarrier. The N baseband signals may be signal that are respectively generated according to by modulation formats based on different radio access technologies. 
     The N signal processors  120 - 1  through  120 -N respectively include a transmission signal processor  121  and a replica signal processor  122 . 
     The transmission signal processor  121  includes a first gain adjuster  1211 , a peak power reducer  1212 , a second gain adjuster  1213 , a modulator  1214 , and an output power corrector  1215 . The output power corrector  1215  may be included in the first gain adjuster  1211 . 
     The first gain adjuster  1211  adjusts the gain of carrier signals multiplexed in a multi-carrier signal so that the transmission output power of the multi-carrier signal transmitted from the antenna  190  via the power amplifier  180  becomes a prescribed reference output power. Specifically, the first gain adjuster  1211  reduces the power of an input baseband signal of a carrier to a prescribed reference output power for the corresponding carrier signal according to a first gain adjustment value reported from the control processor  110 . 
     Meanwhile, in the first embodiment, the first gain adjuster  1211  includes an output power corrector  1215 . The output power corrector  1215  corrects the error between the power of a carrier signal to which a peak power reduction process has been applied by the peak power reducer  1212  and the prescribed reference output power for the corresponding carrier signal. Specifically, the output power corrector  1215  corrects the power of an input baseband signal according to a power correction value reported from the control processor  110 . 
     The power correction value may be multiplied by the first gain adjustment value so as to be reported from the control processor  110  to the first gain adjuster  1211  together with the first gain adjustment value. In addition, the first gain adjuster  1211  that includes the output power corrector  1215  may be configured so as to adjust the power of an input baseband signal according to the first gain adjustment value multiplied by the power correction value. 
     The peak power reducer  1212  reduces the power of the multi-carrier signal in which the respective carrier signals are multiplexed to be equal to or smaller than a prescribed peak power threshold set by the control processor  110 , by multiplying the input baseband signal of a carrier by a peak reduction value (reduction coefficient). The peak reduction value is generated by the peak reduction value calculator  130 . The peak reduction value calculator  130  calculates the peak reduction value based on a comparison between a replica of the multi-carrier signal and a peak power threshold reported from the control processor  110 . The replica of the multi-carrier signal is a signal obtained by combining respective carrier signals to which the process by the peak power reducer  1212  is not applied. The replica of the multi-carrier signal is generated by the process performed by the replica signal processor  122 . 
     The replica signal processor  122  includes a second gain adjuster  1221  and a modulator  1222 . The second gain adjuster  1221  has substantially the same function as that of the second gain adjuster  1213 . Meanwhile, the modulator  1222  has substantially the same function as that of the modulator  1214 . The baseband signal output from the first gain adjuster  1211  is input to the second gain adjuster  1221 . The baseband signal whose gain has been adjusted by the second gain adjuster  1221  is input to the modulator  1222 . The modulator  1222  performs frequency shift by a carrier frequency reported from the control processor  110  to generate a replica of the carrier signal. 
     The replicas of carrier signals generated respectively by the modulators  1222  in the signal processors  120 - 1  through  120 -N are input to the peak reduction value calculator  130 .  FIG. 2  is an exemplary configuration diagram of the peak reduction value calculator  130 . As illustrated in  FIG. 2 , the peak reduction value calculator  130  includes a combiner  131 , a power calculator  132 , a comparator  133 , and a coefficient calculator  134 . 
     The combiner  131  generates a replica of the multi-carrier signal by combining (multiplexing) the replicas of the carrier signals respectively generated by the modulators  1222  in the signal processors  120 - 1  through  120 -N. The power calculator  132  calculates the power value of the multi-carrier signal to which the peak power reduction process by the peak power reducer  1212  has not been applied, using the replica of the multi-carrier signal generated by the synthesizer  131 . The comparator  133  compares the power value calculated by the power calculator  132  and the peak power threshold reported from the control processor  110  and detects the different (error) between them. The coefficient calculator  134  calculates the peak reduction value (reduction coefficient) by which the baseband signal of the carrier is to be multiplied in the peak power reducer  1212 , according to the detected difference. The calculated peak reduction value is fed to the peak power reducer  1212  of each of the N transmission signal processors  121 . 
     In the N peak power reducers  1212 , the baseband signals of the respective carriers are multiplied by the same peak reduction value respectively in the period of time in which the replica of the multi-carrier signal exceeds the peak power threshold. By the reduction process applied to the baseband signal of each carrier by the peak power reducer  1212 , the PAPR of the multi-carrier signal in which the respective carrier signals are combined (multiplexed) is reduced. 
     Meanwhile, in the example illustrated in  FIGS. 1A-1C , the peak reduction value calculator  130  calculates the peak reduction value using the replica of the multi-carrier signal treated with a correction according to the power correction value. That is, in the example illustrated in  FIGS. 1A-1C , the replica of the carrier signal treated with a power correction by the output power corrector  1215  is generated by each replica signal processor  122 , and the generated replica signal of each carrier is input to the peak reduction value calculator  130 . However, the peak reduction value calculator  130  may be configured so as to calculate the peak reduction value using the replica signal of the multi-carrier signal that is not treated with the correction according to the power correction value. In this case, each replica signal processor  122  may be configured so as to generate a replica of the carrier signal that is not treated with the correction according to the power correction value. Specifically, each replica signal processor  122  may be configured to further include a gain adjuster having substantially the same function as that of the first gain adjuster  1211  that does not include the output power corrector  1215 . The same baseband signal as the baseband signal that is input to the first gain adjuster  1211  is input to the gain adjuster added to each replica signal processor  122 . Then, the baseband signal that is output from the added gain adjuster is input to the second gain adjuster  1221 . 
     The second gain adjuster  1213  adjusts the gain of the carrier signal included in the multi-carrier signal so that the multi-carrier signal before conversion to radio frequency is converted from digital to analog at the optimal operation point of the digital to analog converter  160 . Specifically, the second gain adjuster  1213  increases the power of an input baseband signal according to a second gain adjustment value. The second gain adjustment value is set in advance in the second gain adjuster  1213 . 
     The modulator  1214  applies frequency shift by a carrier frequency reported from the control processor  110  to the baseband signal whose gain has been adjusted by the second gain adjuster  1213  and generates a carrier signal. The modulator  1214  includes an oscillator such as Numerically Controlled Oscillator (NCO), for example. 
     The combiner  140  combines the carrier signals respectively generated by the modulators  1214  in the signal processors  120 - 1  through  120 -N and generates a multi-carrier signal. The respective carrier signals multiplexed in the generated multi-carrier signal are arranged at a prescribed frequency spacing according to the respective carrier frequencies. The distortion compensator  150  compensates for the distortion of the multi-carrier signal generated due to the amplification of the power of the multi-carrier signal by the power amplifier  180 . The digital to analog converter  160  converts the multi-carrier signal that has been through the process performed by the distortion compensator  150  from digital to analog. The radio frequency converter  170  converts the multi-carrier signal that has been converted into analog to a signal of prescribed radio frequency. The power amplifier  180  amplifies the transmission output power of the multi-carrier signal of radio frequency to a prescribed reference output power. The antenna  190  emits the multi-carrier signal whose transmission output power has been amplified by the power amplifier  180  into the space outside the radio device  100 . 
     The control processor  110  controls the processes of the signal processor  120 . Specifically, the control processor  110  receives control information for each carrier signal from a host device (not illustrated in the drawing). The control information includes the carrier frequency information, the first gain adjustment value, and the radio access technology (RAT) information. 
     The control processor  110  generates control values for controlling the processes of the signal processor  120  using the received control information. Control values include the first gain adjustment value, the peak power threshold, the carrier frequency information, and the power correction value. A value obtained by multiplying the first gain adjustment value by the power correction value may be generated as the first gain adjustment value and the power correction value. The control processor  110  makes the signal processor  120  execute processes according to the generated control values. Specifically, the control processor  110  gives the first gain adjustment value, the carrier frequency information, and the power correction value to the signal processor  120 . The value obtained by multiplying the first gain adjustment value by the power correction value may be given to the signal processor  120  as the first gain adjustment value and the power correction value. In addition, the control processor  110  gives the peak power threshold to the peak reduction value calculator  130 . 
     The control processor  110  includes correction value generators  111 - 1  through  111 -N, a threshold reporting unit  112 , and frequency reporting units  113 - 1  through  113 -N. 
     For the correction value generators  111 - 1  through  111 -N, the processing target for each is one carrier signal that is different from each other in the N carrier signals multiplexed in a multi-carrier signal. The correction value generator  111  receives the first gain adjustment value for the processing-target carrier signal from the host device. In addition, the correction value generator  111  receives information of the carrier frequency for each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value generator  111  generates the power correction value for the processing-target carrier signal using the received information of the carrier frequency. The correction value generator  111  multiplies the first gain adjustment value by the generated power correction value. The correction value generator  111  transmits the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     The threshold reporting unit  112  receives the information of the radio access technology (RAT) for the transmission-target multi-carrier signal from the host device. The threshold reporting unit  112  gives a prescribed peak power threshold according to the radio access technology to the peak reduction value calculator  130 . 
     For the frequency reporting units  113 - 1  through  113 -N, the processing target for each is one carrier signal that is different from each other in the N carrier signals multiplexed in the multi-carrier signal. The frequency reporting unit  113  reports the carrier frequency of the processing-target carrier signal to the modulator  1214  and the modulator  1222  in the signal processor  120  provided for the corresponding carrier signal. Specifically, the frequency reporting unit  113  receives information of the carrier frequency of the processing-target carrier signal from the host device. The frequency reporting unit  113  gives the carrier frequency information to the modulator  1214  and the modulator  1222  in the signal processor  120  provided for the corresponding carrier signal. 
     The correction value generators  111 - 1  through  111 -N respectively include a power correction value table  1111  and a correction value obtaining unit  1112 . 
       FIG. 3  is an exemplary diagram of a power correction value table according to the first embodiment. As illustrated in  FIG. 3 , the power correction value is recorded in a power correction value table  1111  with respect to occupied bandwidth of the multi-carrier signal. The occupied bandwidth of a multi-carrier signal represents the frequency bandwidth between the lowest carrier frequency and the highest carrier frequency in the carrier frequencies of a plurality of (N) carrier signals multiplexed in the multi-carrier signal. The example of the content in  FIG. 3  indicates that the broader the occupied bandwidth, the larger the gain (power correction value) added by the output power corrector  1215 . Meanwhile, the power correction value table in the present embodiment is not limited to the example of the content in  FIG. 3 , and an arbitrary power correction value may be set for each occupied bandwidth of a multi-carrier signal. In addition, the segments of the occupied bandwidths are not limited to those in the example of the content in  FIG. 3 , and they may be set arbitrarily. 
     The reason why the power correction value is recorded in the power correction value table  1111  for each occupied bandwidth of the multi-carrier signal is explained below with respect to  FIG. 4A ,  FIG. 4B ,  FIG. 5 ,  FIG. 6A , and  FIG. 6B . 
       FIG. 4A  is an exemplary diagram of a multi-carrier signal having a narrow occupied bandwidth for which the peak power suppression process has not been applied.  FIG. 4B  is an exemplary diagram of a multi-carrier signal having a broad occupied bandwidth for which the peak power suppression process has not been applied.  FIG. 4A  and  FIG. 4B  present exemplary illustrations of multi-carrier signals in which two (N=2) carrier signals are combined (multiplexed). In addition, the multi-carrier signals illustrated in  FIG. 4A  and  FIG. 4B  represent signals in which carrier signals to which the peak power reduction process has not been applied by the peak power reducer  1212  in the signal processor  120 . Note that the occupied bandwidth of the multi-carrier signal may be narrow in accordance with the carrier frequencies of the respective carrier signals as in  FIG. 4A  in some cases, and it may be broad as in  FIG. 4B  in some cases. 
       FIG. 5  is an exemplary diagram of changes with time in the power of multi-carrier signals.  FIG. 5  illustrates changes with time in the power of a multi-carrier signal having a narrow occupied bandwidth as in  FIG. 4A  and changes with time in the power of a multi-carrier signal having a broad occupied bandwidth as in  FIG. 4B  together with the envelope of the multi-carrier signals. As illustrated in  FIG. 5 , changes with time in the power of the multi-carrier signal having a broad occupied bandwidth are faster compared with changes with time in the power of the multi-carrier signal having a narrow occupied bandwidth. That is, the multi-carrier signal having a narrow occupied bandwidth follows the envelope over relatively long time intervals, whereas the multi-carrier signal having a broad occupied bandwidth follows the envelope over relatively short time intervals. 
     The reason why the multi-carrier signal having abroad occupied bandwidth follows the envelope over relatively short time intervals compared with the multi-carrier signal having a narrow occupied bandwidth may be explained as follows for example. That is, when there is a carrier signal of higher frequency assuming the carrier signal of low frequency multiplexed in the multi-carrier signal as a reference, that is, when there is a carrier signal whose amplitude changes faster with time, the multi-carrier signal includes a component whose amplitude changes faster with time. For this reason, the changes with time in the amplitude (power) of the multi-carrier signal becomes faster when there is a carrier signal of a higher frequency with respect to the carrier signal at the low-frequency side, that is, when the occupied bandwidth of the multi-carrier is broader. 
     As described above, changes with time in multi-carrier signals differ according to the width of the occupied bandwidth of the multi-carrier signals. Specifically a multi-carrier signal having a broad occupied bandwidth follows the envelope over relatively short time intervals, and therefore, a multi-carrier signal having a broad occupied bandwidth includes a signal having a large power compared with a the multi-carrier signal having a narrow occupied bandwidth. For this reason, when a reduction process such as clipping or the like is applied in the same manner using a peak power threshold such as the one illustrated in  FIG. 5 , the power of the signal regarded as the target of the reduction process as the signal that exceeds the peak power threshold differs according to the width of the occupied bandwidth of the multi-carrier signals. 
     Specifically, a multi-carrier signal having a narrow occupied bandwidth follows the envelope over relatively long time intervals as illustrated in  FIG. 5 . For this reason, in a multi-carrier signal having a narrow occupied bandwidth, the power of the signal regarded as the target of the reduction process as the signal that exceeds the peak power threshold is relatively small. Therefore, when the reduction process is applied using the same peak power threshold as that for a multi-carrier signal having a broad occupied bandwidth, the power reduced in the multi-carrier signal having a narrow occupied bandwidth is relatively small as illustrated in  FIG. 6A .  FIG. 6A  is an exemplary diagram of a multi-carrier signal having a narrow occupied bandwidth to which a peak power reduction process has been applied. 
     On the other hand, a multi-carrier signal having a broad occupied bandwidth follows the envelope over relatively short intervals as illustrated in  FIG. 5 . For this reason, in a multi-carrier signal having a broad occupied bandwidth, the power of the signal regarded as the target of the reduction process as the signal that exceeds the peak power threshold is relatively large. Therefore, when the reduction process is applied using the same peak power threshold as that for a multi-carrier signal having a narrow occupied bandwidth, the power reduced in the multi-carrier signal having a broad occupied bandwidth is relatively large as illustrated in  FIG. 6B .  FIG. 6B  is an exemplary diagram of a multi-carrier signal having a broad occupied bandwidth to which a peak power reduction process has been applied. 
     Thus, the magnitude of the power to which the reduction process is applied in each carrier signal differs according to the width of the occupied bandwidth of the multi-carrier signal, when the process is to be applied using the same peak reduction value (reduction coefficient). Specifically, the power reduced by the process performed by the peak power reducer  1212  becomes larger as the occupied bandwidth of the multi-carrier signal becomes wider. 
     Meanwhile,  FIG. 4A ,  FIG. 4B ,  FIG. 5 ,  FIG. 6A , and  FIG. 6B  are merely examples for explaining that the magnitude of the power reduced by the peak power reducer  1212  differs according to the width of the occupied bandwidth. For example, even when there are three carrier signals multiplexed in the multi-carrier signal (N=3), it can still be said that the power reduced by the peak power reducer  1212  becomes larger as the occupied bandwidth of the multi-carrier signal becomes wider. In addition, for example, assuming that the respective carrier signals multiplexed in the multi-carrier signal have the same bandwidth and that the respective carrier signals are arranged at the same frequency spacing, the occupied bandwidth of the multi-carrier signal becomes wider as the number of carrier signals multiplexed in the multi-carrier signal increases. That is, under such an assumption, it can also be said that the power reduced by the peak power reducer  1212  becomes larger as the number (N) of the carrier signals increases, that is, as the occupied bandwidth of the multi-carrier signal becomes wider. 
     As mentioned earlier, the output power corrector  1215  suppresses the error between the power of a carrier signal to which the peak power reduction process has been applied by the peak power reducer  1212  and the prescribed reference output power for the corresponding carrier signal. Specifically, the output power corrector  1215  corrects the power of the carrier signal according to the power correction value reported from the control processor  110 . However, the magnitude of the power reduced by the peak power reducer  1212  is different according to the width of the occupied bandwidth of the multi-carrier signal, and therefore, the value of the error regarded as the target of the correction, that is, the power correction value differs according to the width of the occupied bandwidth of the multi-carrier signal. Therefore, in order for the correction value generator  111  to report the power correction value according to the width of the occupied bandwidth of the multi-carrier signal to the first gain adjuster  1211 , the power correction value for each occupied bandwidth of the multi-carrier signal is recorded in advance in the power correction value table  1111 . 
     The correction value obtaining unit  1112  receives the first gain adjustment value for the processing-target carrier signal from the host device. In addition, the correction value obtaining unit  1112  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value obtaining unit  1112  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. In addition, the correction value obtaining unit  1112  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  1111 . The correction value obtaining unit  1112  multiplies the first gain adjustment value by the power correction value. The correction value obtaining unit  1112  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     The first gain adjuster  1211  receives the first gain adjustment value multiplied by the power correction value from the correction value obtaining unit  1112 . The first gain adjuster  1211  adjusts the power of the baseband signal of the processing-target carrier in accordance with the prescribed reference output power for the carrier signal, according to the first gain adjustment value multiplied by the power correction value. That is, the first gain adjuster  1211  adjusts the power of the baseband signal of the processing-target carrier treated with a correction process by the output power corrector  1215 . 
     Meanwhile, the correction value obtaining unit  1112  may also be configured so as to vive the power correction value and the first gain adjustment value separately to the first gain adjuster  1211 . In this case, the first gain adjuster  1211  may be configured so as to reduce, according to the received first gain adjustment value, the power of the input baseband signal of a carrier in accordance with the prescribed reference output power for the carrier signal. The output power corrector  1215  may be configured to correct, according to the received power correction value, the output power of the baseband signal of the carrier that has been reduced according to the first gain adjustment value. 
     Through the processes performed by the correction value generator  111  and the output power corrector  1215  described above, the error between the transmission output power of a carrier signal to which the peak power reduction process has been applied and the reference output power for the carrier signal is suppressed in advance in accordance with the width of the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of the carrier signals multiplexed in the multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     An example of the method for transmitting the multi-carrier signal executed by the radio device  100  is explained.  FIG. 7  is an exemplary illustration of the process flow for the transmission of a multi-carrier signal executed by the radio device according to the first embodiment. In the example illustrated in  FIG. 7 , control values set by the control processor  110  are the first gain adjustment value multiplied by the power correction value, the peak power threshold, and the carrier frequency. Meanwhile, in  FIG. 7 , the respective processes in step S 1003 , step S 1004 , and step S 1005  through step S 1006  may be performed in parallel in terms of time. 
     When a series of processes for transmitting a multi-carrier signal start (step S 1001 ), the control processor  110  receives control information from a host device (step S 1002 ). Specifically, the correction value obtaining unit  1112  receives the first gain adjustment value for the processing-target carrier signal and information of the carrier frequency of each carrier signal. The threshold reporting unit  112  receives information of the radio access technology for the transmission-target multi-carrier signal from the host device. The frequency reporting unit  113  receives information of the carrier frequency of the processing-target carrier signal from the host device. 
     In step S 1003 , the threshold reporting unit  112  gives a prescribed peak power threshold according to the radio access technology to the peak reduction value calculator  130 . The peak reduction value calculator  130  receives the peak power threshold from the threshold reporting unit  112 . The peak reduction value calculator  130  sets the peak power threshold as the power threshold for the multi-carrier signal in which carrier signals generated by the respective transmission signal processors  121  are multiplexed. 
     In step S 1004 , the frequency reporting unit  113  gives the value of the carrier frequency to the modulators  1214 ,  1222  in the signal processor  120  provided for the corresponding carrier signal. The modulators  1214 ,  1222  receive the carrier frequency information of the processing-target carrier signal from the frequency reporting unit  113 . The modulators  1214 ,  1222  sets the received carrier frequency information as the carrier frequency for modulating an input baseband signal. 
     In step S 1005 , the correction value obtaining unit  1112  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  1112  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  1111 . The correction value obtaining unit  1112  multiplies the first gain adjustment value by the obtained power correction value. The correction value obtaining unit  1112  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     In step S 1006 , the first gain adjuster  1211  receives the first gain adjustment value multiplied by the power correction value from the correction value obtaining unit  1112 . The first gain adjuster  1211  sets the first gain adjustment value multiplied by the power correction value as the gain adjustment value to be adjusted by this first gain adjuster  1211  that includes the output power corrector  1215 . 
     In step S 1007 , the radio device  100  starts the transmission of a multi-carrier signal according to the set control values. Specifically, the first gain adjuster  1211  receives a baseband signals of carrier transmitted from application. Then, the respective transmission signal processors  121  generate carrier signals according to the set control values. The carrier signals generated by the respective transmission signal processors  121  are combined by the combiner  140  and a multi-carrier signal is generated. The multi-carrier signal generated by the combiner  140  is output via the antenna  190  after being subjected to the processes by the distortion compensator  150 , the digital to analog converter  160 , the radio frequency converter  170 , and the power amplifier  180 . The series of processes are terminated when the transmission of the multi-carrier signal ends (step S 1008 ). 
     The radio device  100  is configured by hardware illustrated in  FIG. 8 , for example.  FIG. 8  is an exemplary hardware configuration diagram of the radio device according to the first embodiment. As illustrated in  FIG. 8 , a radio device  200  includes a processor  210 , a memory  220 , a Field Programmable Gate Array (FPGA)  230 , a DAC  240 , an up converter  250 , a power amplifier  260 , a filter  270 , and an antenna  280 . 
     The processor  210  is a logic circuit such as a Central Processor (CPU) that performs operation processes. The processor  210  controls the operations of the respective circuit elements included in the radio device  200 . The processor  210  corresponds to the control processor  110  and the peak reduction value calculator  130 . 
     The memory  220  is a device in which a processing program executed by the processor  210 , data used for the processing by the processor  210 , and data of the processing result by the processor  210  are stored. The memory  220  includes the power correction value table  1111 . 
     The FPGA  230  includes a communication interface  2301  and a Digital Pre-distortion (DPD)  2302 . 
     The communication interface  2301  is an interface for transmitting and receiving a data signal of base band and control signals between the radio device  200  and a host device (not illustrated in the drawing) according to a prescribed communication standard. Examples of the communication standard include Common Public Radio Interface (CPRI) and Open Base Station Architecture Initiative (OBSAI), and the like. The communication interface  2301  forwards a data signal received from the host device to the DPD  2302 , and forwards a control signal received from the host device to the processor  210 , for example. 
     The DPD  2302  receives the data signal of base band transmitted from the host device via the communication interface  2301 . The DPD  2302  applies digital processing to the received data signal according to control signals received from the processor  210 . The DPD  2302  corresponds to the signal processors  120 - 1  through  120 -N, the peak reduction value calculator  130 , the combiner  140 , and the distortion compensator  150 . 
     The DAC  240  converts the data signal processed by the DPD  2302  from digital to analog. The DAC  240  corresponds to the digital to analog converter  160 . The up converter  250  up-converts the analog-converted data signal to radio frequency. The up converter  250  corresponds to the radio frequency converter  170 . 
     The power amplifier  260  amplifies the transmission output power of the data signal of radio frequency to a prescribed reference output power. The power amplifier  260  corresponds to the power amplifier  180 . The filter  270  is a splitter that separates the data signal transmitted via the antenna  280  and the data signal received via the antenna  280 . The antenna  280  emits the data signal received via the filter  270  to a radio terminal device (not illustrated in the drawing) that communicates with the radio device  200 , and the antenna  280  guides the data signal received from a radio terminal device to the filter  270 . The antenna  280  corresponds to the antenna  190 . 
     Thus, the following effects may be obtained with the radio device according to the first embodiment. That is, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and a prescribed reference power of the carrier signal is suppressed in accordance with the width of the occupied bandwidth of the multi-carrier signal in the process of the generation of each of the carrier signals multiplexed in the multi-carrier signal. As a result, with the radio device according to the first embodiment, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     Second Embodiment 
     In the first embodiment, the output power corrector  1215  is included in the first gain adjuster  1211 . For this reason, the error between the transmission output power of a carrier signal to which a peak power reduction process is applied and the reference output power for the carrier signal is suppressed before the peak power reduction process is applied to the carrier signal. However, the radio device may be configured so as to suppress such an error after the peak power reduction process is applied to the carrier signal. 
       FIGS. 9A-9B  are exemplary function configuration diagrams of a radio device according to the second embodiment. In  FIG. 9 , in the circuit elements of a radio device  300  according to the second embodiment, the same circuit elements as those in the radio device  100  (see  FIGS. 1A-1C ) are indicated by the same reference numerals as the reference numerals of the circuit elements of the radio device  100 . The radio device  300  is configured by hardware illustrated in  FIG. 8 , for example. Note that the distortion compensator  150 , the DAC  160 , the radio frequency converter  170 , the power amplifier  180 , and the antenna  190  are substantially the same in the first and second embodiments, and thus they are omitted in  FIGS. 9A-9B . 
     As illustrated in  FIGS. 9A-9B , the radio device  300  includes a control processor  310  instead of the control processor  110  (see  FIG. 1C ). In addition, the radio device  300  includes signal processors  320  instead of the signal processors  120  (see  FIG. 1B ). 
     The signal processors  320 - 1  through  320 -N respectively include a transmission signal processor  321  instead of the transmission signal processor  121  (see  FIG. 1B ). In addition, the signal processors  320 - 1  through  320 -N respectively include a replica signal processor  322  instead of the replica signal processor  122  (see  FIG. 1B ). 
     The transmission signal processor  321  includes a first gain adjuster  3211  instead of the first gain adjuster  1211  (see  FIG. 1B ). The transmission signal processor  321  includes a second gain adjuster  3212  instead of the second gain adjuster  1213  (see  FIG. 1B ). The transmission signal processor  321  includes an output power corrector  3213  instead of the output power corrector  1215  (see  FIG. 1B ). The output power corrector  3213  may be included in the second gain adjuster  3212 . 
     The first gain adjuster  3211  adjusts the gain of carrier signals multiplexed into the multi-carrier signal so that the transmission output power of the multi-carrier signal transmitted from the antenna  190  via the power amplifier  180  becomes a prescribed reference output power. Specifically, the first gain adjuster  3211  reduces the power of the input baseband signal of a carrier to a prescribed reference output power for the corresponding carrier signal according to a first gain adjustment value reported from the control processor  310 . 
     Thus, the first gain adjuster  3211  has a similar function as that of the first gain adjuster  1211 . However, unlike the first gain adjuster  1211 , the first gain adjuster  3211  does not include the output power corrector  1215  (see  FIG. 1B ). 
     The second gain adjuster  3212  adjusts the gain of carrier signals multiplexed in the multi-carrier signal so that the multi-carrier signal before conversion to radio frequency is converted from digital to analog at the optimal operation point of the digital to analog converter  160 . Specifically, the second gain adjuster  3212  increases the power of an input baseband signal according to a second gain adjustment value reported from the control processor  310 . 
     Thus, the second gain adjuster  3212  has a similar function as that of the second gain adjuster  1213 . However, the second gain adjustment value is reported from the control processor  310  to the second gain adjuster  3212 , while the second gain adjustment value is set in advance in the second gain adjuster  1213 . In addition, unlike the second gain adjuster  1213 , the second gain adjuster  3212  includes the output power corrector  3213 . 
     The output power corrector  3213  corrects the error between the power of a carrier signal to which a peak power reduction process has been applied by the peak power reducer  1212  and the prescribed reference output power for the corresponding carrier signal. Specifically, the output power corrector  3213  corrects the power of an input baseband signal according to a power correction value reported from the control processor  310 . 
     Thus, the output power corrector  3213  has a similar function as that of the output power corrector  1215 . However, the output power corrector  3213  differs from the output power corrector  1215  included in the first gain adjuster  1211 , in that the output power corrector  3213  is included in the second gain adjuster  3212 . 
     The power correction value may be multiplied by the second gain adjustment value so as to be reported from the control processor  310  to the second gain adjuster  3212  together with the second gain adjustment value. In this case, the second gain adjuster  3212  including the output power corrector  3213  may be configured so as to adjust the power of an input baseband signal according to second gain adjustment value multiplied by the power correction value. 
     The replica signal processor  322  generate a carrier signal to which the process by the peak power reducer  1212  is not applied. The replica signal processor  322  includes a second gain adjuster  3221  instead of the second gain adjuster  1221  (see  FIG. 1B ). The second gain adjuster  3221  has substantially the same function as that of the second gain adjuster  3212  included in the transmission signal processor  321 . The output power corrector  3222  has substantially the same function as that of the output power corrector  3222  included in the transmission signal processor  321 . 
     In the example illustrated in  FIG. 9A , the peak reduction value calculator  130  calculates the peak reduction value using a replica of a multi-carrier signal treated with a correction according to the power correction value. That is, in the example illustrated in  FIG. 9A , the replica of a carrier signal treated with the power correction by the output power corrector  3222  is generated by each replica signal processor  322 , and the generated replica signal of each carrier is input to the peak reduction value calculator  130 . However, the peak reduction value calculator  130  may be configured so as to calculate the peak reduction value using a replica of a multi-carrier signal that is not treated with the correction according to the power correction value. In this case, each replica signal processor  322  may be configured so as to generate a replica of a carrier signal that is not treated with the correction according to the power correction value. Specifically, each replica signal processor  322  may be configured so as not to include the output power corrector  3222  in the second gain adjuster  3221 . 
     The control processor  310  includes adjustment value reporting units  311 - 1  through  311 -N instead of the correction value generators  111 - 1  through  111 -N (see  FIG. 1C ). In addition, the control processor  310  includes correction value generators  312 - 1  through  312 -N. 
     The adjustment value reporting unit  311  receives the first gain adjustment value for the processing-target carrier signal from the host device. The adjustment value reporting unit  311  gives the first gain adjustment value to the first gain adjuster  3211  provided for the corresponding carrier signal. Thus, the adjustment value reporting unit  311  has a similar function as a part of the function of the correction value generator  111  (see  FIG. 1C ). However, the adjustment value reporting unit  311  differs from the correction value generator  111  in that the adjustment value reporting unit  311  does not generate and transmit the power correction value. 
     The correction value generator  312  holds in advance the second gain correction value for the processing-target carrier signal. In addition, the correction value generator  312  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value generator  312  generates the power correction value for the processing-target carrier signal using the received information of each carrier frequency. The correction value generator  312  multiplies the held second gain adjustment value by the generated power correction value. The correction value generator  312  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     Thus, the correction value generator  312  has a similar function as that of the correction value generator  111  in generating the power correction value using information of each carrier frequency received from a host device. However, the correction value generator  312  differs from the correction value generator  111  that receives the first gain adjustment value from a host device, in that the correction value generator  312  holds in advance the second gain adjustment value. In addition, the correction value generator  312  differs from the correction value generator  111  that gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211 , in that the correction value generator  312  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221 . 
     The correction value generators  312 - 1  through  312 -N respectively include a power correction value table  3121  and a correction value obtaining unit  3122 . 
     In the power correction value table  3121 , the power correction value is recorded for each occupied bandwidth of the multi-carrier signal. The power correction value table  3121  may be a table similar to the power correction value table  1111  illustrated in  FIG. 3 . 
     The correction value obtaining unit  3122  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value obtaining unit  3122  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  3122  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  3121 . The correction value obtaining unit  3122  multiplies the second gain adjustment value held in advance by the obtained power correction value. The correction value obtaining unit  3122  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     The second gain adjuster  3212  receives the second gain adjustment value multiplied by the power correction value from the correction value obtaining unit  3122 . The second gain adjuster  3212  adjusts the output power of the processing-target carrier signal so that digital to analog converter  160  operates at the optimal operation point, according to the second gain adjustment value multiplied by the power correction value. That is, the second gain adjuster  3212  adjusts the power of the baseband signal of the processing-target carrier treated with the correction process by the output power corrector  3213 . The second gain adjuster  3221  operates in a manner similar to that of the second gain adjuster  3212 . 
     Meanwhile, the correction value obtaining unit  3122  may also be configured so as to give the power correction value and the second gain adjustment value separately to the second gain adjuster  3212 ,  3221  provided for the corresponding carrier signal. In this case, the second gain adjuster  3212  may be configured so as to reduce, according to the received second gain adjustment value, the power of an input baseband signal of a carrier in accordance with a prescribed reference output power. The output power corrector  3213  included in the second gain adjuster  3212  may also be configured so as to correct, according to the received power adjustment value, the output power of the baseband signal of the carrier reduced in accordance with the second gain adjustment value. The second gain adjuster  3221  and the output power corrector  3222  may be configured so as to operate in a manner similar to that of the second gain adjuster  3212  and the output power corrector  3213 . 
     Through the processes performed by the correction value generator  312  and the output power corrector  3213  described above, the error between the transmission output power of the carrier signal to which a peak power reduction process is applied and the reference output power for the carrier signal is suppressed in accordance with the width of the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     Meanwhile, the correction value generator  312  may further be configured as explained below. 
     Instead of holding the second gain adjustment value in the correction value obtaining unit  3122  in advance, the power correction value multiplied by the second gain adjustment value is recorded for each occupied bandwidth of the multi-carrier signal in the power correction value table  3121 , as illustrated in  FIG. 10 .  FIG. 10  is an example of the power correction value table according to the second embodiment. 
     The correction value obtaining unit  3122  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value obtaining unit  3122  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  3122  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  3121 . The obtained power correction value has been multiplied by the second gain adjustment value in advance. The correction value obtaining unit  3122  gives the obtained power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     The second gain adjuster  3212  receives the power correction value multiplied by the second gain adjustment value from the correction value obtaining unit  3122 . The second gain adjuster  3212  adjusts the power of an input carrier signal so that the digital to analog converter  160  operates at the optimal operation point, according to the power correction value multiplied by the second gain adjustment. That is, the second gain adjuster  3212  adjusts the power of the baseband signal of the processing-target carrier treated with the correction process by the output power corrector  3213 . The second gain adjuster  3221  operates in a manner similar to that of the second gain adjuster  3212 . 
     According to a configuration such as the one described above, the error between the transmission output power of a carrier signal to which a peak power reduction process is applied and the reference output power for the carrier signal is also suppressed in accordance with the width of the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     In addition, according to a configuration such as the one described above, the process for multiplying the second gain adjustment value by the power correction value in the correction value generator  312  is not required, and therefore, it becomes possible to simplify and speed up the processing in the control processor  310  that includes the correction value generator  312 . 
     An example of the method for transmitting the multi-carrier signal executed by the radio device  300  is explained.  FIG. 11  is an exemplary illustration of the process flow for the transmission of a multi-carrier signal executed by the radio device according to the second embodiment. In the example illustrated in  FIG. 11 , control values set by the control processor  310  are the first gain adjustment value, the peak power threshold, the carrier frequency, and the power correction value multiplied by the second gain adjustment value. Meanwhile, in  FIG. 11 , the respective processes in step S 2003 , step S 2004 , step S 2005 , and step S 2006  through step S 2007  may be performed in parallel in terms of time. 
     When a series of processes for transmitting a multi-carrier signal start (step S 2001 ), the control processor  310  receives control information from a host device (step S 2002 ). Specifically, the adjustment value reporting unit  311  receives the first gain adjustment value for the processing-target carrier signal from the host device. The threshold reporting unit  112  receives information of the radio access technology for the transmission-target multi-carrier signal from the host device. The correction value obtaining unit  3122  receives information of the carrier frequency of each carrier signal from the host device. The frequency reporting unit  113  receives information of the carrier frequency of the processing-target carrier signal from the host device. 
     In step S 2003 , the adjustment value reporting unit  311  gives the first gain adjustment value to the first gain adjuster  3211  provided for the corresponding carrier signal. The first gain adjuster  3211  receives the first gain adjustment value for the processing-target carrier signal from the adjustment value reporting unit  311 . The first gain adjuster  3211  sets the received first gain adjustment value as the value for adjusting the power of an input baseband signal of a carrier to the prescribed reference output power for the carrier signal. 
     In step S 2004 , the threshold reporting unit  112  gives a prescribed peak power threshold according to the radio access technology to the peak reduction value calculator  130 . The peak reduction value calculator  130  receives the peak power threshold from the threshold reporting unit  112 . The peak reduction value calculator  130  sets the peak power threshold as the power threshold for the multi-carrier signal in which carrier signals generated by the respective transmission signal processors  321  are multiplexed. 
     In step S 2005 , the frequency reporting unit  113  gives the value of the carrier frequency to the modulators  1214 ,  1222  in the signal processor  320  provided for the corresponding carrier signal. The modulators  1214 ,  1222  receive the carrier frequency information of the processing-target carrier signal from the frequency reporting unit  113 . The modulators  1214 ,  1222  set the received carrier frequency information as the carrier frequency for modulating an input baseband signal. 
     In step S 2006 , the correction value obtaining unit  3122  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  3122  obtains the power correction value according to the occupied bandwidth from the power correction value table  3121 . The obtained power correction value has been multiplied by the second gain adjustment value in advance. That is, a fixed value is used as the second gain adjustment value without depending on the occupied bandwidth of the multi-carrier signal, and therefore, the value obtained by multiplying the power correction value according to the occupied bandwidth by the second gain adjustment value may be stored in advance in the power correction value table  3121 . The correction value obtaining unit  3122  gives the obtained power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     In step S 2007 , the second gain adjuster  3212  receives the power correction value multiplied by the second gain adjustment value from the correction value obtaining unit  3122 . The second gain adjuster  3212  sets the power correction value multiplied by the second gain adjustment value as the gain adjustment value to be adjusted by this second gain adjuster  3212  that includes the output power corrector  3213 . The second gain adjuster  3221  performs processes similar to these processes performed by the second gain adjuster  3212 . 
     In step S 2008 , the radio device  300  starts the transmission of a multi-carrier signal according to the set control values. Specifically, the first gain adjuster  3211  receives baseband signals of carriers generated by the application. The respective transmission signal processors  321  generate carrier signals according to the set control values. The carrier signals generated by the respective transmission signal processors  321  are combined by the combiner  140 , and a multi-carrier signal is generated. The multi-carrier signal generated by the combiner  140  is transmitted via the antenna  190  after being subjected to the processes by the distortion compensator  150 , the digital to analog converter  160 , the radio frequency converter  170 , and the power amplifier  180 . The series of processes are terminated when the transmission of the multi-carrier signal ends (step S 2009 ). 
     As described above, with the radio device  300  according to the second embodiment, an effect that is similar to the effect obtained with the radio device  100  according to the first embodiment may also be obtained. In addition, with the radio device  300  according to the second embodiment, it becomes possible to simplify and speed up the process for correcting error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal. 
     Third Embodiment 
     In the first embodiment, the radio device suppresses the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal before the peak power reduction process is applied to the carrier signal. In addition, in the first embodiment, the radio device holds in advance the power correction value for each occupied bandwidth of the multi-carrier signal in order to correct such an error. However, the radio device may also be configured so as to generate the power correction value for the carrier signals multiplexed in the transmission-target multi-carrier signal while these carrier signals are being generated. 
       FIGS. 12A-12B  are exemplary function configuration diagrams of a radio device according to the third embodiment. In  FIGS. 12A-12B , in the constituent elements of a radio device  400  according to the third embodiment, the same circuit elements as those in the radio device  100  (see  FIGS. 1A-1C ) are indicated by the same reference numerals as the reference numerals of the circuit elements of the radio device  100 . The radio device  400  is configured by hardware illustrated in  FIG. 8 , for example. Note that the distortion compensator  150 , the DAC  160 , the radio frequency converter  170 , the power amplifier  180 , and the antenna  190  are substantially the same in the first and third embodiments, and thus they are omitted in  FIGS. 12A-12B . 
     As illustrated in  FIGS. 12A-12B , a radio device  400  includes a control processor  410  instead of the control processor  110  (see  FIG. 1C ). The control processor  410  includes correction value generators  411 - 1  through  411 -N instead of the correction value generators  111 - 1  through  111 -N (see  FIG. 1C ). 
     The correction value generator  411  stores initial values of the power correction values for processing-target carrier signals, for each occupied bandwidth of the multi-carrier signal. For example, the correction value generator  411  stores a power correction value table such as the one illustrated in  FIG. 3 . 
     The correction value generator  411  receives the first gain adjustment value for the processing-target carrier signal from a host device. In addition, the correction value generator  411  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal. The correction value generator  411  calculates the occupied bandwidth of the multi-carrier signal using the received information of each carrier frequency. The correction value generator  411  selects the initial value of the power correction value according to the calculated occupied bandwidth from the initial values of the power correction values stored in advance. The correction value generator  411  holds the initial value of the power correction value as the power correction value to be used by the output power corrector  1215  provided for the corresponding carrier signal. The correction value generator  411  multiplies the received first gain adjustment value by the held power correction value. The correction value generator  411  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     Meanwhile, after the transmission of the multi-carrier signal starts, the correction value generator  411  generates the power correction value from the processing-target carrier signal. Specifically, the correction value generator  411  calculates a first power and a second power. The first power is the power of the carrier signal before the peak power reduction process is applied to it, that is, specifically, the power of the baseband signal of the carrier that is input to the peak power reducer  1212 . The second power is the power of the carrier signal after the peak power reduction process is applied to it, that is, specifically, the power of the baseband signal of the carrier that is output from the peak power reducer  1212 . The correction value generator  411  calculates a new power correction value using the difference between the first power and the second power. 
     In a manner similar to that in the first embodiment, the peak power reducer  1212  reduces the power of the multi-carrier signal in which the respective carrier signals are multiplexed so as to make it equal to or smaller than a prescribed peak power threshold set by the control processor  410 , by multiplying the base band of the input carrier by a peak reduction value. The peak reduction value is calculated by the peak reduction value calculator  130  by comparing a replica of the multi-carrier signal generated through the process performed by the replica signal processor  122  with a peak power threshold reported from the control processor  110 . The replica of the multi-carrier signal used for the calculation of the peak reduction value has the same occupied bandwidth as that of the multi-carrier signal. For this reason, it can be said that the peak reduction value is a value calculated according to the occupied bandwidth of the multi-carrier signal, and therefore, it can be said that the second power that is output from the peak power reducer  1212  using the peak reduction value is also a power to which a reduction process has been applied according to the occupied bandwidth of the multi-carrier signal. Therefore, it can be said that the power correction value generated from the difference value between the first power and the second power is a value generated according to the occupied bandwidth of the multi-carrier signal. In other words, it can be said that the power correction value generated from the difference value between the first power and the second power depends on the occupied bandwidth of the multi-carrier signal. 
     The correction value generator  411  generates a power correction value that is newly used by the output power corrector  1215  provided for the corresponding carrier signal, from the difference value between the first power and the second power and the power correction value that has been already held by the correction value generator  411 . For example, the correction value generator  411  calculates the weighted average of the difference value between the first power and the second power and the power correction value that has been already held by the correction value generator  411 . The correction value generator  411  holds the newly generated power correction value. The correction value generator  411  multiplies the received first gain adjustment value by the held power correction value. The correction value generator  411  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     Meanwhile, the generation process for the power correction value after the start of the transmission of the multi-carrier signal may be repeated a prescribed number of times at a prescribed time interval. With the repeated execution of the generation process for the power correction value, it becomes possible to improve the accuracy in suppressing the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal. 
     As described above, the correction value generator  411  has a similar function to that of the correction value generator  111  (see  FIG. 1C ) in generating a power correction value and giving the generated the first gain adjustment value multiplied by the generated the power correction value to the first gain adjuster  1211 . However, the correction value generator  411  differs from the correction value generator  111  in that, after the start of the transmission of the multi-carrier signal, the correction value generator  411  generates the power correction value using the power of the carrier signal before the peak power reduction process and the power of the carrier signal after the peak power reduction process. 
     The correction value generators  411 - 1  through  411 -N respectively include a first power calculator  4111 , a second power calculator  4112 , a difference detector  4113 , a correction value obtaining unit  4114 , and a power correction value table  4115 . 
     The correction value obtaining unit  4114  receives the first gain adjustment value for the processing-target carrier signal from the host device. In addition, the correction value obtaining unit  4114  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The correction value obtaining unit  4114  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  4114  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  4115 . The power correction value table  4115  is a table such as the one illustrated in  FIG. 3  for example. The correction value obtaining unit  4114  holds the obtained power correction value. The correction value obtaining unit  4114  multiplies the received first gain adjustment value by the held power correction value. The correction value obtaining unit  4114  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     After the start of the transmission of the multi-carrier signal, the first power calculator  4111  calculates the first power of the processing-target carrier signal from the baseband signal of the carrier that is input to the peak power reducer  1212  provided for the corresponding carrier signal. The second power calculator  4112  calculates the second power of the processing-target carrier signal from the baseband signal of the carrier that is output from the peak power reducer  1212  provided for the corresponding carrier signal. The difference detector  4113  detects the difference between the first power calculated by the first power calculator  4111  and the second power calculated by the second power calculator  4112 . The correction value obtaining unit  4114  obtains the power difference value detected by the difference detector  4113 . The correction value obtaining unit  4114  calculates the weighted average of the obtained power difference value and the power correction value that has already been held. The correction value obtaining unit  4114  holds the calculated value as a new power correction value. The correction value obtaining unit  4114  multiplies the first gain adjustment value received from the host device by the held power correction value. The correction value obtaining unit  4114  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     As described above, the correction value generator  411  generates the power correction value using the baseband signal of the carrier that is actually processed by the signal processors  120 , and therefore, the power correction value is generated with a good accuracy. 
     The first gain adjuster  1211  receives the first gain adjustment value multiplied by the power correction value from the correction value obtaining unit  4114 . The first gain adjuster  1211  adjusts the power of an input carrier signal in accordance with the prescribed reference output power for the carrier signal, according to the first gain adjustment value multiplied by the power correction value. That is, the first gain adjuster  1211  adjusts the power of the baseband signal of the processing-target carrier treated with a correction process by the output power corrector  1215 . 
     Meanwhile, the correction value obtaining unit  4114  may also be configured so as to give the power correction value and the first gain adjustment value separately to the first gain adjuster  1211 . In this case, the first gain adjuster  1211  may also be configured so as to reduce, according to the received first gain adjustment value, the power of an input baseband signal of a carrier in accordance with the prescribed reference output power for the carrier signal. The output power corrector  1215  included in the first gain adjuster  1211  may also be configured to correct, according to the received power correction value, the output power of the baseband signal of the carrier reduced in accordance with the first gain adjustment value. 
     Through the processes performed by the correction value generator  411  and the output power corrector  1215  described above, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is suppressed in accordance with the width of the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     Meanwhile, described above is merely a configuration example of the radio device according to the third embodiment, and for example, the radio device according to the third embodiment may also be configured so as to execute the processes described below. That is, the control processor  410  associates and stores the power correction values generated by the correction value generator  411  with the occupied bandwidths of the multi-carrier signal to be transmitted. The control processor  410  calculates a new bandwidth of a multi-carrier signal using information of carrier frequencies newly reported from a host device. The control processor  410  decides whether or not the power correction value according to the calculated occupied bandwidth has already been stored. When it is decided that the power correction value according to the calculated occupied bandwidth has already been stored, the control processor  410  reports the power correction value according to the calculated occupied bandwidth to the first gain adjuster  1211 . When it is decided that the power correction value according to the calculated occupied bandwidth has not been stored, the control processor  410  generates the power correction value according to the calculated occupied bandwidth through the process performed by the correction value generator  411 , and reports the newly generated power correction value to the first gain adjuster  1211 . According to such a configuration, the radio device  400  does not need to generate a power correction value every time information of the carrier frequency is newly reported from the host device. As a result, according to the configuration described above, it becomes possible to speed up and simplify the process for suppressing the error between the transmission output power of a carrier signal to which a peak power reduction process is applied and the reference output power for the carrier signal. 
     Meanwhile, in the description above, the correction value obtaining unit  4114  obtains the power correction value from the power correction value table  4115  at the time of the start of transmission. However, the radio device  400  may be configured so as not to include the power correction value table  4115 , and the correction value obtaining unit  4114  may be configured so as to hold a default value as the power correction value at the time of the start of transmission. According to such a configuration, during the transmission of the multi-carrier signal, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is also suppressed in accordance with the occupied bandwidth of the multi-carrier signal. 
     An example of the method for transmitting the multi-carrier signal executed by radio device  400  is explained.  FIG. 13  is an exemplary illustration of the process flow for the transmission of a multi-carrier signal executed by the radio device according to the third embodiment. In the example illustrated in  FIG. 13 , control values set by the control processor  410  are the first gain adjustment value multiplied by the power correction value, the peak power threshold, and the carrier frequency. Meanwhile, in  FIG. 13 , the respective processes in step S 3003 , step S 3004 , and step S 3005  may be performed in parallel in terms of time. 
     When a series of processes for transmitting a multi-carrier signal start (step S 3001 ), the control processor  410  receives control information from a host device (step S 3002 ). Specifically, the correction value obtaining unit  4114  receives the first gain adjustment value for the processing-target carrier signal and information of the carrier frequency of each carrier signal. The threshold reporting unit  112  receives information of the radio access technology for the transmission-target multi-carrier signal from the host device. The frequency reporting unit  113  receives the information of the carrier frequency of the processing-target carrier signal from the host device. 
     In step S 3003 , the threshold reporting unit  112  reports the peak power threshold according to the radio access technology to the peak reduction value calculator  130 . The peak reduction value calculator  130  receives the peak power threshold from the threshold reporting unit  112 . The peak reduction value calculator  130  sets the received peak power threshold as the power threshold for the multi-carrier signal in which carrier signals generated by the respective transmission signal processors  321  are multiplexed. 
     In step S 3004 , the frequency reporting unit  113  reports the value of the received carrier frequency to the modulators  1214 ,  1222  in the signal processor  120  provided for the corresponding carrier signal. The modulators  1214 ,  1222  receive the carrier frequency information of the processing-target carrier signal from the frequency reporting unit  113 . The modulators  1214 ,  1222  set the carrier frequency information as the carrier frequency for modulating an input baseband signal. 
     In step S 3005 , the correction value obtaining unit  4114  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  4114  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  4115  and holds the obtained power correction value. The correction value obtaining unit  4114  multiplies the received first gain adjustment value by the held power correction value. The correction value obtaining unit  4114  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     The first gain adjuster  1211  receives the first gain adjustment value multiplied by the power correction value from the correction value obtaining unit  4114 . The first gain adjuster  1211  sets the first gain adjustment value multiplied by the power correction value as the gain adjustment value to be adjusted by the corresponding first gain adjuster  1211  that includes the output power corrector  1215 . 
     In step S 3006 , the radio device  400  starts the transmission of a multi-carrier signal according to the set control values. Specifically, the first gain adjuster  1211  receives baseband signals of carriers transmitted from the application. Then, the respective transmission signal processors  121  generate carrier signals according to the set control values. The carrier signals generated by the respective transmission signal processors  121  are combined by the combiner  140  and a multi-carrier signal is generated. The multi-carrier signal generated by the combiner  140  is transmitted via the antenna  190  after being subjected to the processes by the distortion compensator  150 , the digital to analog converter  160 , the radio frequency converter  170 , and the power amplifier  180 . 
     When the transmission of the multi-carrier signal starts, the processes in step S 3007  through step S 3014  are repeated a prescribed number of times M (M is an arbitrary integer equal to or larger than 1). 
     In step S 3008 , the first power calculator  4111  integrates over a prescribe period of time the power of the baseband signal of the carrier that is input to the peak power reducer  1212  provided for the same carrier signal as that for the first power calculator  4111  to calculate the first power. In step S 3009 , the second power calculator  4112  integrates over a prescribe period of time the power of the baseband signal of the carrier that is output from the peak power reducer  1212  provided for the same carrier signal as that for the second power calculator  4112  to calculate the second power. 
     In step S 3010 , the difference detector  4113  detects the difference between the first power calculated by the first power calculator  4111  in step S 3008  and the second power calculated by the second power calculator  4112  in step S 3009 . The correction value obtaining unit  4114  obtains the difference value detected by the difference detector  4113 . In step S 3011 , the correction value obtaining unit  4114  calculates the weighted average of the power difference value and the power correction value that has already been held, and the correction value obtaining unit  4114  holds the calculated value as a new power correction value. In step S 3012 , the correction value obtaining unit  4114  multiplies the first gain adjustment value received from the host device by the held power correction value. The correction value obtaining unit  4114  gives the first gain adjustment value multiplied by the power correction value to the first gain adjuster  1211  provided for the corresponding carrier signal. 
     In step S 3013 , the first gain adjuster  1211  receives the first gain adjustment value multiplied by the power correction value from the correction value obtaining unit  4114 . The first gain adjuster  1211  sets the first gain adjustment value multiplied by the power correction value as the gain adjustment value to be adjusted by the corresponding first gain adjuster  1211  that includes the output power corrector  1215 . 
     The series of processes are terminated when the transmission of the multi-carrier ends (step S 3015 ). 
     As described above, with the radio device  400  according to the third embodiment, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is suppressed with a good accuracy in accordance with the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal further improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     Fourth Embodiment 
     In the second embodiment, the radio device suppresses the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal after the peak power reduction process is applied to the carrier signal. In addition, in the second embodiment, the radio device holds in advance the power correction value for each occupied bandwidth of the multi-carrier signal in order to correct such an error. However, the radio device may also be configured so as to generate the power correction value for the carrier signals multiplexed in the transmission-target multi-carrier signal while these carrier signals are being generated. 
       FIGS. 14A-14B  are exemplary function configuration diagrams of a radio device according to the fourth embodiment. In  FIGS. 14A-14B , in the circuit elements of a radio device  500  according to the fourth embodiment, the same circuit elements as those in the radio device  300  (see  FIGS. 9A-9B ) are indicated by the same reference numerals as the reference numerals of the circuit elements of the radio device  300 . The radio device  500  is configured by hardware illustrated in  FIG. 8 , for example. Note that the distortion compensator  150 , the DAC  160 , the radio frequency converter  170 , the power amplifier  180 , and the antenna  190  are substantially the same in the first and fourth embodiments, and thus they are omitted in  FIGS. 14A-14B . 
     As illustrated in  FIGS. 14A-14B , the radio device  500  includes a control processor  510  instead of the control processor  310  (see  FIG. 9B ). The control processor  510  includes correction value generators  511 - 1  through  511 -N instead of the correction value generators  312 - 1  through  312 - 2  (see  FIG. 9B ). 
     The correction value generator  511  holds the second gain adjustment value for the processing-target carrier signal in advance. In addition, the correction value generator  511  stores an initial value of the power correction value for the processing-target carrier signal, for each occupied bandwidth of the multi-carrier signal. For example, the correction value generator  511  holds a power correction value table such as the one illustrated in  FIG. 3 . 
     The correction value generator  511  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from a host device. The correction value generator  511  calculates the occupied bandwidth of the multi-carrier signal using the received information of each carrier frequency. The correction value generator  511  selects the initial value of the power correction value according to the calculated occupied bandwidth from the stored initial values of the power correction values. The correction value generator  511  holds the selected initial value of the power correction value as the power correction value to be used by the output power correctors  3213 ,  3222  in the signal processor  320  provided for the corresponding carrier signal. The correction value generator  511  multiplies the second gain adjustment value held in advance by the held power correction value. The correction value generator  511  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     Meanwhile, after the transmission of the multi-carrier signal starts, the correction value generator  511  generates the power correction value using the difference value between the first power and the second power. As described earlier, it can be said that the power correction value calculated using the difference value between the first power and the second power is a value generated according to the occupied bandwidth of the multi-carrier signal. For example, the correction value generator  411  calculates the weighted average of the difference value between the first power and the second power and the power correction value that has already been held. The correction value generator  411  holds the newly generated power correction value. 
     The correction value generator  511  multiplies the second gain adjustment value held in advance by the held power correction value. The correction value generator  511  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     Meanwhile, the generation process for the power correction value after the start of the transmission of the multi-carrier signal may be repeated a prescribed number of times at a prescribed time interval. With the repeated execution of the generation process for the power correction value, it becomes possible to improve the accuracy in suppressing the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal. 
     As described above, the correction value generator  511  has a similar function as that of the correction value generator  312  in generating a power correction value and giving the second gain adjustment value multiplied by the generated power correction value to the second gain adjusters  3212 ,  3221 . However, the correction value generator  511  differs from the correction value generator  312  in that, after the start of the transmission of the multi-carrier signal, the correction value generator  511  generates the power correction value using the power of the carrier signal before the peak power reduction process and the power of the carrier signal after the peak power reduction process. 
     The correction value generators  511 - 1  through  511 -N respectively include a first power calculator  5111 , a second power calculator  5112 , a difference detector  5113 , a correction value obtaining unit  5114 , and a power correction value table  5115 . 
     The correction value obtaining unit  5114  holds the second gain adjustment value for the processing-target carrier signal in advance. The correction value obtaining unit  5114  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from a host device. The correction value obtaining unit  5114  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  5114  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  5115 . The power correction value table  5115  is a table such as the one illustrated in  FIG. 3  for example. The correction value obtaining unit  5114  holds the obtained power correction value. The correction value obtaining unit  5114  multiplies the second gain adjustment value held in advance by the held power correction value. The correction value obtaining unit  5114  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221 , in the signal processor  320  provided for the corresponding carrier signal. 
     After the start of the transmission of the multi-carrier signal, the first power calculator  5111  calculates the first power of the processing-target carrier signal from the baseband signal of the carrier that is input to the peak power reducer  1212  provided for the corresponding carrier signal. The second power calculator  5112  calculates the second power of the processing-target carrier signal from the baseband signal of the carrier that is output from the peak power reducer  1212  provided for the corresponding carrier signal. The difference detector  5113  detects the difference between the first power calculated by the first power calculator  5111  and the second power calculated by the second power calculator  5112 . The correction value obtaining unit  5114  obtains the power difference value detected by the difference detector  5113 . The correction value obtaining unit  5114  calculates the weighted average of the obtained power difference value and the power correction value that has already been held. The correction value obtaining unit  5114  holds the calculated value as a new power correction value. The correction value obtaining unit  5114  multiplies the second gain adjustment value held in advance by the held power correction value. The correction value obtaining unit  5114  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  in the signal processor  320  provided for the corresponding carrier signal. 
     As described above, the correction value generator  511  generates the power correction value that is to be reported to the output power corrector  3213  without holding it in advance. In addition, the correction value generator  511  generates the power correction value using the baseband signals of carriers that are actually processed by the signal processors  320 , and therefore, the power correction value is generated with a good accuracy. 
     The second gain adjuster  3212  receives the power correction value multiplied by the second gain adjustment value from the correction value obtaining unit  5114 . The second gain adjuster  3212  adjusts the power of an input carrier signal so that the digital to analog converter  160  operates at the optimal operation point, according to the power correction value multiplied by the second gain adjustment value. That is, the second gain adjuster  3212  adjusts the power of the baseband signal of the processing-target carrier treated with the correction process by the output power corrector  3213 . Note that the second gain adjuster  3221  operates in a manner similar to that of the second gain adjuster  3212 . 
     Meanwhile, the correction value obtaining unit  5114  may also be configured so as to give the power correction value and the second gain adjustment value separately to the second gain adjuster  3212  provided for the corresponding carrier signal. In this case, the second gain adjuster  3212  may also be configured so as to increase the power of an input baseband signal of a carrier according to the received second gain adjustment value. The output power corrector  3213  included in the second gain adjuster  3212  may also be configured to correct the output power of the baseband signal of the carrier increased in accordance with the second gain adjustment value, according to the received power correction value. The second gain adjuster  3221  and the output power corrector  3222  may also be configured so as to operate in a manner similar to that of the second gain adjuster  3212  and the output power corrector  3213 . 
     Through the processes performed by the correction value generator  511  and the output power corrector  3213  described above, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is suppressed in accordance with the width of the occupied bandwidth of the multi-carrier signal. As a result, the accuracy of the transmission output power of each of carrier signals multiplexed in a multi-carrier signal improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     Meanwhile, described above is merely a configuration example of the radio device according to the fourth embodiment, and the radio device according to the fourth embodiment may also be configured so as to execute the processes described below. That is, the control processor  510  associates and stores the power correction value generated by the correction value generator  511  with the occupied bandwidth of the multi-carrier signal to be transmitted. The control processor  510  calculates the bandwidth of the multi-carrier signal to be transmitted using information of carrier frequencies newly reported from a host device. The control processor  510  decides whether the power correction value corresponding to the calculated bandwidth has already been stored. When it is decided that the power correction value corresponding to the calculated bandwidth has already been stored, the control processor  510  reports the power correction value corresponding to the calculated occupied bandwidth to the second gain adjusters  3212 ,  3221 . When it is decided that the power correction value corresponding to the calculated bandwidth has not been stored, the control processor  510  generates a power correction value corresponding to the calculated occupied bandwidth through the process performed by the correction value generator  511 , and reports the generated power correction value to the second gain adjusters  3212 ,  3221 . According to such a configuration, the radio device  500  does not need to generate the power correction value every time information of the carrier frequency is newly reported from the host device. As a result, according to the configuration described above, it becomes possible to further speed up and simplify the process for suppressing the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal in accordance with the occupied bandwidth of the multi-carrier signal. 
     Meanwhile, in the description above, the correction value obtaining unit  5114  obtains, from the power correction value table  5115 , the power correction value at the time of the start of transmission. However, the radio device  500  may be configured so as not to include the power correction value table  5115 , and the correction value obtaining unit  5114  may be configured so as to hold a default value as the power correction value at the time of the start of transmission. According to such a configuration, during the transmission of the multi-carrier signal, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is also suppressed in accordance with the occupied bandwidth of the multi-carrier signal. 
     An example of the method for transmitting the multi-carrier signal executed by the radio device  500  is explained.  FIG. 15  is an exemplary illustration of the process flow for the transmission of a multi-carrier signal executed by the radio device according to the fourth embodiment. In the example illustrated in  FIG. 15 , control values generated by the control processor  510  are the first gain adjustment value, the peak power threshold, the carrier frequency, and the second gain adjustment value multiplied by the power correction value. Meanwhile, in  FIG. 15 , the respective processes in step S 4003 , step S 4004 , and step S 4005  may be performed in parallel in terms of time. 
     When a series of processes for transmitting a multi-carrier signal start (step S 4001 ), the control processor  510  receives control information from a host device (step S 4002 ). Specifically, the adjustment value reporting unit  311  receives the first gain adjustment value for the processing-target carrier signal from the host device. The threshold reporting unit  112  receives information of the radio access technology for the transmission-target multi-carrier signal from the host device. The correction value obtaining unit  5114  receives information of the carrier frequency of each of the carrier signals multiplexed in the multi-carrier signal from the host device. The frequency reporting unit  113  receives information of the carrier frequency of the processing-target carrier signal from the host device. 
     In step S 4003 , the adjustment value reporting unit  311  gives the received first gain adjustment value to the first gain adjuster  3211  provided for the corresponding carrier signal. The first gain adjuster  3211  receives the first gain adjustment value for the processing-target carrier signal from the adjustment value reporting unit  311 . The first gain adjuster  3211  sets the received first gain adjustment value as the value for adjusting the power of an input baseband signal of a carrier to the prescribed reference output power for the carrier signal. 
     In step S 4004 , the threshold reporting unit  112  reports the prescribed peak power threshold according to the radio access technology to the peak reduction value calculator  130 . The peak reduction value calculator  130  receives the peak power threshold from the threshold reporting unit  112 . The peak reduction value calculator  130  sets the received peak power threshold as the power threshold for the multi-carrier signal in which carrier signals generated by the respective transmission signal processors  121  are multiplexed. 
     In step S 4005 , the frequency reporting unit  113  reports the value of the carrier frequency to the modulators  1214 ,  1222  in the signal processor  320  provided for the corresponding carrier signal. The modulators  1214 ,  1222  receive the carrier frequency information of the processing-target carrier signal from the frequency reporting unit  113 . The modulators  1214 ,  1222  sets the received carrier frequency information as the carrier frequency for modulating an input baseband signal. 
     In step S 4006 , the correction value obtaining unit  5114  calculates the occupied bandwidth of the multi-carrier signal by referring to the received information of the carrier frequencies and subtracting the lowest carrier frequency from the highest carrier frequency. The correction value obtaining unit  5114  obtains the power correction value according to the calculated occupied bandwidth from the power correction value table  5115 , and the correction value obtaining unit  5114  holds the obtained power correction value. The correction value obtaining unit  5114  multiplies the received second gain adjustment value by the held power correction value. The correction value obtaining unit  5114  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  provided for the corresponding carrier signal. 
     The second gain adjuster  3212  receives the second gain adjustment value multiplied by the power correction value from the correction value obtaining unit  5114 . The second gain adjuster  3212  sets the second gain adjustment value multiplied by the power correction value as the gain adjustment value to be adjusted by this second gain adjuster  3212  that includes the output power corrector  3213 . The second gain adjuster  3221  operates in a manner similar to that of the second gain adjuster  3212  to set the second gain adjustment value multiplied by the power correction value. 
     In step S 4007 , the radio device  500  starts the transmission of a multi-carrier signal according to the set control values. Specifically, the first gain adjuster  3211  receives baseband signals of carriers transmitted from the application. Then, the respective transmission signal processors  321  generate carrier signals according to the set control values. The carrier signals generated by the respective transmission signal processors  321  are combined by the combiner  140 , and a multi-carrier signal is generated. The multi-carrier signal generated by the combiner  140  is transmitted via the antenna  190  after being subjected to the processes by the distortion compensator  150 , the digital to analog converter  160 , the radio frequency converter  170 , and the power amplifier  180 . 
     When the transmission of the multi-carrier signal starts, the processes in step S 4008  through step S 4015  are repeated a prescribed number of times M (M is an arbitrary integer equal to or larger than 1). 
     In step S 4009 , the first power calculator  5111  integrates over a prescribe period of time the power of the baseband signal of the carrier that is input to the peak power reducer  1212  provided for the same carrier signal as that for the first power calculator  5111  to calculate the first power. In step S 4010 , the second power calculator  5112  integrates over a prescribe period of time the power of the baseband signal of the carrier that is output from the peak power reducer  1212  provided for the same carrier signal as that for the second power calculator  5112  to calculate the second power. 
     In step S 4011 , the difference detector  5113  detects the difference between the first power calculated by the first power calculator  5111  in step S 4009  and the second power calculated by the second power calculator  5112  in step S 4010 . The correction value obtaining unit  5114  obtains the power difference value detected by the difference detector  5113 . In step S 4012 , the correction value obtaining unit  5114  calculates the weighted average of the obtained power difference value and the held power correction value, and the correction value obtaining unit  5114  holds the calculated value as a new power correction value. In step S 4013 , the correction value obtaining unit  5114  multiplies the second gain adjustment value held in advance with the held power correction value. The correction value obtaining unit  5114  gives the second gain adjustment value multiplied by the power correction value to the second gain adjusters  3212 ,  3221  provided for the corresponding carrier signal. 
     In step S 4014 , the second gain adjuster  3212  receives the second gain adjustment value multiplied by the power correction value from the correction value obtaining unit  5114 . The second gain adjuster  3212  sets the second gain adjustment value multiplied by the power correction value as the gain adjustment value to be adjusted by this second gain adjuster  3212  that includes the output power corrector  3213 . The second gain adjuster  3221  sets the second gain adjustment value multiplied by the power correction value through an operation similar to that of the second gain adjuster  3212 . 
     The series of processes are terminated when the transmission of the multi-carrier ends (step S 4016 ). 
     As described above, with the radio device  500  according to the fourth embodiment, the error between the transmission output power of a carrier signal to which a peak power reduction process has been applied and the reference output power for the carrier signal is suppressed in accordance with the occupied bandwidth of the multi-carrier signal with a good accuracy. As a result, the accuracy of the transmission output power of each of the carrier signals multiplexed in the multi-carrier signal further improves regardless of the width of the occupied bandwidth of the multi-carrier signal. 
     As described above, with a radio device according to an aspect of the embodiments, while reducing the peak power of a multi-carrier signal in which a plurality of carrier signals are multiplexed, the accuracy of the transmission output power of each of the carrier signals may be improved. 
     All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.