JP2010109630A - Transmitter and signal transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumed during the transmission of a signal which switches a modulation system with time duration. <P>SOLUTION: A base station device 101 includes a soft clipping part 115 which acquires a modulation system for a transmission signal whose modulation system switches as time passes, determines upper limit power of the transmission signal on the basis of the modulation system, and reduces a part of the power of the transmission signal that surpasses the upper limit power, to the upper limit power or smaller. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission apparatus and a signal transmission method, and more particularly to a transmission apparatus and a signal transmission method for transmitting a signal whose modulation scheme is switched over time.

  OFDM (Orthogonal Frequency Division Multiplexing) or the like is a multiplexing scheme that realizes high-speed communication in mobile communication or the like. The OFDM system has also been decided to be adopted for the next generation PHS.

  In communication using these methods, a plurality of subcarriers and codes are multiplexed when a transmission signal is generated. Therefore, an orthogonal frequency division multiplexed transmission signal has a very large instantaneous power (peak power) relative to the average power of the signal. It has the feature of having. FIG. 7 is a diagram showing a waveform of power of a transmission signal in communication using the OFDM method. The ratio of the peak power to the average power is referred to as a peak-to-average power ratio (Peak-to-Average Power Ratio, PAPR, unit is dB).

  Here, characteristics of the amplifier that amplifies the transmission signal will be described. FIG. 8 is a diagram showing the input / output characteristics of the amplifier and the power efficiency with respect to the input. The difference between the output power of the amplifier at the operating point and the saturation value of the output power (saturated output power) is called backoff. It is shown that the power efficiency of the amplifier improves as the backoff decreases due to an increase in input power or the like.

  In order to amplify a signal having a large PAPR, that is, a peak power higher than the average power with a small distortion, it is necessary to increase the back-off, and the power efficiency is lowered.

  As a technique for solving such a problem, there is CFR (Crest Factor Reduction) processing such as soft clipping and hard clipping for reducing peak power, and these techniques are described in Patent Document 1, for example.

  The signal distribution before and after the CFR processing will be described. FIG. 10 is a diagram illustrating a distribution of signal power before CFR processing. FIG. 11 is a diagram illustrating a distribution of signal power after CFR processing. In these figures, the horizontal axis is PAPR, and a larger value represents a signal having a larger signal power. The vertical axis is CCDF (Complementary Cumulative Distribution Function, complementary cumulative distribution function), which indicates the probability of occurrence of each signal. It can be seen that a signal with PAPR = 10 dB is generated about 0.1% before the CFR processing, but is not generated at all after the CFR processing.

The CFR process is defined by a CFR value (unit: dB) representing how much the PAPR is lowered. For example, CFR value = 4 means that the PAPR of the signal is lowered by 4 dB, and the peak power is actually reduced so that the PAPR is lowered by 4 dB. CFR value = 0 means that CFR processing is not performed. In general OFDM communication using adaptive modulation, the CFR value is constant regardless of the modulation method.
JP 2007-306346 A

  However, when peak power is reduced by CFR processing or the like, modulation accuracy (Error Vector Magnet, EVM) deteriorates due to deterioration of amplitude information. If processing with a large CFR value is performed, the degradation of modulation accuracy also increases.

  In communication that performs adaptive modulation in which a modulation scheme is switched with time (time slot), a required EVM is determined for each modulation scheme, and a CFR value is derived for each of the required EVMs. When the CFR value is constant regardless of the modulation scheme, the CFR value is the most among the CFR values derived for each modulation scheme in order to satisfy each required EVM in communication by all modulation schemes. Fixed to a small value.

  In this case, during communication using a modulation method other than the modulation method having the highest required EVM, CFR processing is performed with a CFR value smaller than the CFR value that satisfies the required EVM. For this reason, the peak power becomes larger than the peak power required for realizing the required EVM of the modulation method, and there is room for reduction of power consumption.

  For example, in modulation with a high modulation multi-level number such as 256QAM executed in the next generation PHS, a high EVM is required, and thus the CFR value needs to be considerably reduced. When this CFR value is applied to all modulation schemes, in a modulation scheme with a low required EVM, CFR processing with a very small value is performed as compared with the CFR value necessary to satisfy the required EVM. At this time, since the peak power is significantly larger than the peak power necessary for realizing the required EVM, there is a large room for reducing power consumption.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a transmission device and a signal transmission method that reduce power consumed in transmission of a signal whose modulation scheme changes over time.

  In order to achieve the above object, a transmission apparatus according to the present invention is based on a modulation scheme acquisition unit that acquires a modulation scheme and a modulation scheme that is acquired by the modulation scheme acquisition unit of a transmission signal whose modulation scheme changes over time. Then, an upper limit power determining means for determining an upper limit power of the transmission signal, and an excess power reducing means for reducing a portion of the power of the transmission signal that exceeds the upper limit power to the upper limit power or less.

  Further, the transmission device according to the present invention has a control voltage determination unit that determines a control voltage based on the modulation scheme acquired by the modulation scheme acquisition unit, and a saturated input power that varies according to the control voltage. And a power amplifying means for amplifying a portion of the power of the transmission signal output from the excess power reducing means that is less than the saturated input power with an intended amplification factor.

  In the transmission apparatus according to the present invention, the control voltage determination unit determines the control voltage so that the saturation input power of the power amplification unit is equal to or higher than the upper limit power determined by the upper limit power determination unit. .

  Furthermore, in the transmission apparatus according to the present invention, the transmission signal is a signal obtained by multiplexing a plurality of element signals, and the modulation scheme acquired by the modulation scheme acquisition unit is modulated by the modulation scheme of the plurality of component signals. This is the modulation system with the highest multi-level number.

  In the transmission apparatus according to the present invention, the modulation scheme of the transmission signal is switched for each time-divided time slot.

  In the transmission apparatus according to the present invention, the transmission signal is a signal multiplexed by orthogonal frequency division multiplexing.

  Furthermore, the signal transmission method according to the present invention is based on a modulation scheme acquisition step for acquiring a modulation scheme of a transmission signal whose modulation scheme changes over time, and the transmission signal based on the modulation scheme acquired in the modulation scheme acquisition step. An upper limit power determining step for determining the upper limit power, and an excess power reducing step for reducing a portion of the power of the transmission signal that exceeds the upper limit power to the upper limit power or less.

  The power consumed by transmitting a signal whose modulation method changes over time is reduced.

(First embodiment)
In the first embodiment, a configuration using soft clipping processing for performing reduction processing corresponding to the magnitude of the peak power is shown for the peak power of the transmission signal. By suppressing the peak power to the upper limit power determined according to the modulation scheme, power consumption is reduced during communication using a modulation scheme other than the modulation scheme having the highest modulation multilevel number.

  FIG. 1 is a diagram illustrating a configuration of a base station apparatus 101 according to the first embodiment.

  The base station apparatus 101 transmits signals multiplexed by the OFDM method using adaptive modulation to the mobile station apparatus. The base station apparatus 101 includes a CPU 102, a transmission signal processing unit 103, a drain voltage generation unit 104, an amplifier 105, a reception processing unit 106, a memory 107, a switching unit 108, and an antenna 109.

  When the base station apparatus 101 transmits a signal, the antenna 109 transmits a signal input from the amplifier 105 via the switching unit 108 as a radio wave. Further, when the base station apparatus 101 receives a signal, the antenna 109 receives a radio wave and outputs the received radio wave to the reception processing unit 106 via the switching unit 108.

  The switching unit 108 switches the connection destination of the antenna 109 between the amplifier 105 and the reception processing unit 106 according to the operation status of the base station apparatus 101.

  When the base station apparatus 101 transmits a signal, the switching unit 108 outputs the output of the amplifier 105 to the antenna 109 with the connection destination of the antenna 109 as the amplifier 105.

  When the base station apparatus 101 receives a signal, the switching unit 108 uses the connection destination of the antenna 109 as the reception processing unit 106 and outputs the output of the antenna 109 to the reception processing unit 106.

  The reception processing unit 106 receives the signal output from the antenna 109 via the switching unit 108, and performs processing such as AD conversion and demodulation on the received signal to generate reception data. The reception processing unit 106 outputs the generated reception data to the CPU 102.

  The CPU 102 controls the operation of the base station apparatus 101 as a whole. CPU 102 receives a signal transmitted from the mobile station device via antenna 109, switching unit 108, and reception processing unit 106. Based on SINR (Signal-to-Interference plus Noise power Ratio) of the received signal, the CPU 102 switches the modulation method of the transmission signal transmitted from the base station apparatus 101 to the mobile station apparatus with time. The modulation scheme is switched, for example, for each time-slotted time slot.

  In addition, the number of mobile station apparatuses with which the base station apparatus 101 communicates also changes, for example, for each time slot, and the base station apparatus 101 transmits subchannel signals (element signals) that are signals transmitted to the respective mobile station apparatuses. Transmits an orthogonal frequency division multiplexed OFDM signal. For each subchannel signal, CPU 102 determines the modulation scheme based on the SINR of the signal received from the mobile station apparatus that is the transmission destination of the subchannel signal.

  The transmission signal processing unit 103 is composed of a semiconductor circuit or the like, and performs transmission signal processing based on a modulation method determined by the CPU 102. The transmission signal processing unit 103 includes a serial / parallel conversion unit 110, a subchannel signal modulation unit 111, an adder 112, an IFFT unit 113, a signal interpolation unit 114, a soft clipping unit 115, a GI addition unit 116, a symbol shaping unit 117, and a DA converter. 118 and a quadrature modulation unit 119.

  The serial / parallel conversion unit 110 divides the transmission signal processed by the transmission signal processing unit 103 into a plurality of subchannel signals by serial / parallel conversion.

  The subchannel signal modulator 111 modulates each of the plurality of subchannel signals output from the serial / parallel converter 110 according to the modulation scheme determined by the CPU 102.

  The adder 112 performs a negative addition process (subtraction process) on the output of the soft clipping unit 115 with respect to the output of the subchannel signal modulation unit 111.

  The IFFT unit 113 performs inverse Fourier transform on the output of the adder 112.

  The signal interpolation unit 114 performs an interpolation process on the output of the IFFT unit 113.

  The GI addition unit 116 adds a guard interval to the output of the signal interpolation unit 114 to prevent interference due to delayed waves.

  The symbol shaping unit 117 performs window shaping processing on the output of the GI adding unit 116 to reduce the out-of-band spectrum.

  The DA converter 118 performs DA conversion processing on the output of the symbol shaping unit 117.

  The quadrature modulation unit 119 performs quadrature modulation processing on the output of the DA converter 118.

  The soft clipping unit 115 calculates a reduction value for clipping processing. Here, the clipping process is a process of reducing a portion of the signal power exceeding the upper limit power to the upper limit power.

  The clipping process is executed to reduce the PAPR of the transmission signal output from the signal interpolation unit 114. A CFR value (unit: dB), which is a reduction amount of PAPR, is derived from a required EVM defined for each modulation method. FIG. 3 is an example of the CFR value and drain voltage derived for each modulation method. The drain voltage is a numerical value used in the drain voltage generation unit 104 described later, and is stored in the memory 107.

  The upper limit power used in the soft clipping unit 115 is an upper limit value of transmission signal power set to reduce the PAPR by the CFR value shown in FIG. These CFR values are determined in advance from simulation or the like.

  This upper limit power is stored in the memory 107 in association with the modulation method.

  As described above, the base station apparatus 101 performs communication with the mobile station apparatus using a modulation scheme that switches for each time slot, and the number of mobile station apparatuses (users) also changes for each time slot. FIG. 4 is a diagram illustrating an example of communication performed by the base station apparatus 101.

  As illustrated in FIG. 4, the soft clipping unit 115 acquires a modulation scheme having the highest modulation multi-level number among modulation schemes applied to communication performed in each time slot. For example, in slot 1, the modulation scheme having the highest modulation multi-level number is 16QAM. At this time, as shown in FIG. 3, the CFR value is 4.0 dB, and the drain voltage is 28V.

  The soft clipping unit 115 determines the upper limit power of the transmission signal based on the modulation scheme with the highest number of modulation multilevels acquired. Specifically, the soft clipping unit 115 reads the upper limit power stored in association with the acquired modulation scheme from the memory 107 and sets it as the upper limit power of the transmission power.

  The soft clipping unit 115 calculates a reduction value in the adder 112 from the upper limit power and the power of the transmission signal output from the signal interpolation unit 114.

  The soft clipping unit 115 includes an upper limit power comparison unit 120, an excess power detection unit 121, a time domain filter unit 122, an FFT unit 123, and a frequency domain filter unit 124.

  The upper limit power comparison unit 120 compares the upper limit power with the power of the transmission signal output from the signal interpolation unit 114.

  The excess power detection unit 121 detects a difference from the upper limit power for the power of the transmission signal determined to be larger than the upper limit power in the comparison by the upper limit power comparison unit 120.

  The difference detected by the excess power detection unit 121 is converted into frequency component data by the FFT unit 123 after unnecessary time components are removed by the time domain filter unit 122. Further, the frequency domain filter unit 124 removes unnecessary frequency components from the output of the FFT unit 123.

  The soft clipping unit 115 outputs the output of the frequency domain filter unit 124 to the adder 112 as a reduced value.

  The adder 112 subtracts the reduction value output from the soft clipping unit 115 from the output of the subchannel signal modulation unit 111, so that a portion of the transmission signal output from the signal interpolation unit 114 exceeds the upper limit power. It is suppressed to a value equal to the upper limit power.

  The signal output from the transmission signal processing unit 103 is amplified by the amplifier 105 and output to the switching unit 108.

  In the present embodiment, the drain voltage (control voltage) applied to the amplifier 105 is further determined according to the modulation method.

  FIG. 9 is a diagram illustrating input / output characteristics of the amplifier 105 with respect to different drain voltages. If the drain voltage is lowered, the saturated output power is lowered, and the drain voltage acts as a control voltage for controlling the saturated output power.

  In the amplifier 105, when the input power is increased, the input power when the output power reaches the saturation output power is set as the saturation input power. The amplifier 105 amplifies a portion of the signal input from the transmission signal processing unit 103 that is less than the saturation input power with an intended amplification factor. As shown in FIG. 9, the saturation input power also varies depending on the applied drain voltage.

  In the present embodiment, the drain voltage generation unit 104 determines the drain voltage of the amplifier 105 according to the modulation method. If the determined drain voltage is used, the saturation input power becomes equal to or higher than the upper limit power used in the soft clipping unit 115.

  Furthermore, the back-off of the amplifier 105 is reduced by determining the drain voltage of the amplifier 105 so that the difference between the saturated input power and the upper limit power of the soft clipping unit 115 becomes small.

  The operation of the drain voltage generation unit 104 will be described below.

  Drain voltage generation unit 104 includes DC / DC converters 125, 126, 127, 128 and a selector 129. The DC / DC converters 125, 126, 127, and 128 output the drain voltages 24V, 28V, 30V, and 32V shown in FIG. 3, respectively. The selector 129 selects any one of the outputs of the DC / DC converters 125, 126, 127, and 128.

  The selector 129 obtains the modulation scheme having the highest modulation multi-level number of the transmission signal of the target slot from the CPU 102, and based on this modulation scheme, the modulation scheme defined as shown in FIG. One is selected from the outputs of the DC / DC converters 125, 126, 127, and 128 while considering the start timing of the slot so that the drain voltage corresponding to is supplied to the amplifier 105. The output selected by the selector 129 is supplied as the drain voltage of the amplifier 105.

  That is, as with the soft clipping unit 115, the drain voltage generation unit 104 is also set to the modulation method having the highest modulation multi-level number among the modulation methods applied to communication performed in the time slot in each time slot. Based on this, the drain voltage of the amplifier 105 is determined.

  Next, the operation of the base station apparatus 101 will be described using a flowchart.

  FIG. 5 is a flowchart showing the operation of the base station apparatus 101 according to the present invention. The base station apparatus 101 performs the operation shown in this flowchart at the beginning of the time slot.

  The base station apparatus 101 allocates the subchannel signal to the mobile station apparatus (user) (S101).

  Next, the soft clipping unit 115 and the drain voltage generation unit 104 of the base station apparatus 101 use the modulation scheme having the highest modulation multi-level number among the modulation schemes of communication executed in the time slot as a control reference. (S102).

  Next, the soft clipping unit 115 determines the upper limit power based on the acquired modulation method, and the drain voltage generation unit 104 determines the drain voltage of the amplifier 105 based on the acquired modulation method (S103).

  Then, the base station apparatus 101 starts communication with the mobile station apparatus to which the subchannel signal is assigned (S104).

  With the above operation, in base station apparatus 101 that performs communication by adaptive modulation, the upper limit power of soft clipping section 115 and the drain voltage of amplifier 105 are switched according to the modulation scheme.

  By switching the upper limit power in accordance with the modulation method, the power consumed in transmission of a signal whose modulation method is switched over time is reduced.

  Further, the back-off is reduced by determining the drain voltage so that the difference between the saturated input power of the amplifier 105 and the upper limit power of the soft clipping unit 115 becomes small. As shown in FIG. 8, the power efficiency of the amplifier 105 improves as the backoff decreases. Therefore, the power efficiency of the amplifier 105 is improved by determining the drain voltage as described above.

(Second embodiment)
In the second embodiment, a configuration using a hard clipping process for performing a reduction process that uniformly suppresses peak power exceeding the upper limit power to the upper limit power is shown.

  FIG. 2 is a diagram illustrating the configuration of the base station apparatus 201 according to the second embodiment.

  The base station apparatus 201 transmits signals multiplexed by the OFDM method using adaptive modulation to the mobile station apparatus.

  The operation of the base station apparatus 201 is the same as that of the base station apparatus 101 according to the first embodiment except for the operation related to the clipping process. Here, the description about the same part as the base station apparatus 101 which concerns on 1st embodiment is abbreviate | omitted suitably.

  The base station apparatus 201 includes a CPU 102, a transmission signal processing unit 203, a drain voltage generation unit 104, an amplifier 105, a reception processing unit 106, a memory 107, a switching unit 108, and an antenna 109. Except for the transmission signal processing unit 203, each unit is the same as each unit of the base station apparatus 101.

  The transmission signal processing unit 203 includes a semiconductor circuit or the like, and performs transmission signal processing based on a modulation method determined by the CPU 102. The transmission signal processing unit 203 includes a serial-parallel conversion unit 110, a subchannel signal modulation unit 111, an IFFT unit 113, a signal interpolation unit 114, a hard clipping unit 215, a GI addition unit 116, a symbol shaping unit 117, a DA converter 118, and orthogonal modulation. Part 119.

  The serial / parallel converter 110 divides the transmission signal into a plurality of subchannel signals by serial / parallel conversion.

  The subchannel signal modulator 111 modulates each of the plurality of subchannel signals output from the serial / parallel converter 110 according to the modulation scheme determined by the CPU 102.

  IFFT section 113 performs inverse Fourier transform on the output of subchannel signal modulation section 111.

  The signal interpolation unit 114 performs an interpolation process on the output of the IFFT unit 113.

  Based on the modulation scheme determined by the CPU 102, the hard clipping unit 215 performs a clipping process that reduces the portion of the transmission signal power output from the signal interpolation unit 114 that exceeds the upper limit power to the upper limit power.

  The upper limit power used in the hard clipping unit 215 is an upper limit value of transmission signal power set to reduce the PAPR by the CFR value shown in FIG. These CFR values are determined in advance from simulation or the like.

  This upper limit power is stored in the memory 107 in association with the modulation method.

  As shown in FIG. 4, the hard clipping unit 215 acquires the modulation scheme having the highest modulation multi-level number among the modulation schemes applied to the communication performed in the time slot in each time slot.

  The hard clipping unit 215 determines the upper limit power of the transmission signal based on the modulation scheme with the highest number of modulation multilevels acquired. Specifically, the hard clipping unit 215 reads the upper limit power stored in association with the acquired modulation scheme from the memory 107 and sets it as the upper limit power of the transmission power.

  Then, the hard clipping unit 215 reduces the portion of the transmission signal power output from the signal interpolation unit 114 that exceeds the upper limit power to the upper limit power.

  The GI adding unit 116 adds a guard interval to the output of the hard clipping unit 215 to prevent interference due to delayed waves.

  The symbol shaping unit 117 performs window shaping processing on the output of the GI adding unit 116 to reduce the out-of-band spectrum.

  The DA converter 118 performs DA conversion processing on the output of the symbol shaping unit 117.

  Except for the transmission signal processing unit 203 described above, the base station apparatus 101 according to the first embodiment is the same as the base station apparatus 101, and a description thereof will be omitted.

  Next, the operation of the base station apparatus 201 will be described using a flowchart.

  FIG. 6 is a flowchart showing the operation of the base station apparatus 201 according to the second embodiment. The base station apparatus 201 performs the operation shown in this flowchart at the beginning of the time slot.

  The base station apparatus 201 allocates the subchannel signal to the mobile station apparatus (user) (S201).

  Next, the hard clipping unit 215 and the drain voltage generation unit 104 of the base station apparatus 201 use the modulation scheme having the highest modulation multi-level number among the modulation schemes for communication executed in the time slot as a control reference. (S202).

  Next, the hard clipping unit 215 determines the upper limit power based on the acquired modulation method, and the drain voltage generation unit 104 determines the drain voltage of the amplifier 105 based on the acquired modulation method (S203).

  Then, the base station apparatus 101 starts communication with the mobile station apparatus to which the subchannel signal is assigned (S204).

  With the above operation, the base station apparatus 201 that performs communication by adaptive modulation switches the upper limit power of the hard clipping unit 215 according to the modulation method, so that the power consumed by the transmission of the signal whose modulation method is switched over time is reduced. Reduced.

  In addition, since the drain voltage of the amplifier 105 is switched according to the modulation method, the power efficiency in the amplifier 105 is also improved.

  The present invention is not limited to these embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

  For example, in the embodiment shown in the present invention, a configuration using soft clipping processing or hard clipping processing for peak value reduction is shown, but the present invention is not limited to this configuration, and PTS (Partial Transmit Sequence). , SLM (Selected Mapping), Insert Dummy Signal, etc. may be used.

  Further, in the embodiment shown in the present invention, a configuration is shown in which one is selected from the outputs of a plurality of DC / DC converters 125, 126, 127, and 128 and supplied as a drain voltage as a back-off control of the amplifier 105. However, the present invention is not limited to this configuration. For example, a voltage source capable of adjusting the output voltage may be used, and the back-off control may be performed by a method other than the drain voltage control. Good.

  In addition, in the present embodiment, the configuration of the base station apparatus that performs communication by the OFDM scheme has been described. However, the present invention is not limited to this configuration, and other signals that instantaneously transmit a large value are transmitted. The present invention can also be applied to a communication device of a system.

It is a figure which shows the structure of the base station apparatus which concerns on 1st embodiment. It is a figure which shows the structure of the base station apparatus which concerns on 2nd embodiment. It is an example of the CFR value and drain voltage derived | led-out for every modulation system. It is a figure which shows an example of the communication which a base station apparatus performs. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 1st embodiment. It is a flowchart which shows operation | movement of the base station apparatus which concerns on 2nd embodiment. It is a figure which shows the waveform of the power of the transmission signal in the communication by an OFDM system. It is a figure which shows the input-output characteristic of an amplifier, and the power efficiency with respect to an input. It is a figure which shows the input / output characteristic of the amplifier with respect to different drain voltages. It is a figure which shows distribution of the signal power before a CFR process. It is a figure which shows distribution of the signal power after a CFR process.

Explanation of symbols

  101 base station apparatus, 102 CPU, 103 transmission signal processing unit, 104 drain voltage generation unit, 105 amplifier, 106 reception processing unit, 107 memory, 108 switching unit, 109 antenna, 110 series-parallel conversion unit, 111 subchannel signal modulation unit 112 adder, 113 IFFT unit, 114 signal interpolation unit, 115 soft clipping unit, 116 GI addition unit, 117 symbol shaping unit, 118 DA converter, 119 quadrature modulation unit, 120 upper limit power comparison unit, 121 excess power detection unit, 122 time domain filter unit, 123 FFT unit, 124 frequency domain filter unit, 125 DC / DC converter, 126 DC / DC converter, 127 DC / DC converter, 128 DC / DC converter, 129 selector, 201 base station equipment , 203 transmission signal processing section, 215 hard clipping unit.

Claims (7)

A modulation scheme acquisition means for acquiring a modulation scheme of a transmission signal whose modulation scheme is switched over time;
Upper limit power determining means for determining the upper limit power of the transmission signal based on the modulation scheme acquired by the modulation scheme acquiring means;
Excess power reducing means for reducing a portion of the power of the transmission signal that exceeds the upper limit power to the upper limit power or less;
A transmission apparatus comprising: The transmission apparatus according to claim 1,
Control voltage determining means for determining a control voltage based on the modulation scheme acquired by the modulation scheme acquiring means;
A saturation input power that varies according to the control voltage, and a portion of the power of the transmission signal that is output from the excess power reduction means that is less than the saturation input power is amplified with an intended amplification factor. Power amplification means;
The transmission device further comprising: The transmission device according to claim 2,
The control voltage determining means determines the control voltage so that the saturation input power of the power amplifying means is equal to or higher than the upper limit power determined by the upper limit power determining means;
A transmission apparatus characterized by the above. The transmission device according to any one of claims 1 to 3,
The transmission signal is a signal in which a plurality of element signals are multiplexed,
The modulation scheme acquired by the modulation scheme acquisition means is the modulation scheme having the highest modulation multi-level number in the modulation scheme of the plurality of element signals.
A transmission apparatus characterized by the above. The transmission device according to any one of claims 1 to 4,
The modulation method of the transmission signal is switched for each time-divided time slot.
A transmission apparatus characterized by the above. The transmission device according to any one of claims 1 to 5,
The transmission signal is a signal multiplexed by orthogonal frequency division multiplexing.
A transmitting apparatus characterized by the above. A modulation method acquisition step for acquiring a modulation method of a transmission signal whose modulation method is switched over time;
An upper limit power determination step for determining an upper limit power of the transmission signal based on the modulation scheme acquired in the modulation scheme acquisition step;
Of the power of the transmission signal, an excess power reduction step of reducing a portion exceeding the upper limit power to the upper limit power or less;
A signal transmission method comprising:

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