JP2002271292A - Ofdm-transmitting device and method, and ofdm-receiving device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a non-linear distortion by the symbol, without changing the transmission power of a transmission signal itself. SOLUTION: An OFDM-transmitting device 1 for transmitting an orthogonal frequency division multiple(OFDM) signal comprises an OFDM modulation block 12, in which an input signal is subjected to inverse Fourier transformation by the symbol, to generate the OFDM signal of a base band; a DC component calculation block 13 for calculating the DC component of the OFDM signal in each OFDM symbol; and a DC component applying block 14 for adding the calculated DC component to the OFDM signal output from the OFDM modulation block 12 in each OFDM symbol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an orthogonal frequency division multiplex (OFDM).
exing) O applied to digital broadcasting etc. by the transmission method
The present invention relates to an FDM transmitting apparatus and method, and an OFDM receiving apparatus and method.

[0002]

2. Description of the Related Art In recent years, as a method for transmitting digital signals, orthogonal frequency division multiplexing (OFDM) has been proposed.
A modulation scheme called quency division multiplexing has been proposed. In this OFDM system, a number of orthogonal subcarriers (subcarriers) are provided in a transmission band, and data is allocated to the amplitude and phase of each subcarrier.
PSK (Phase Shift Keying) and QAM (Quadrature A)
This is a method of digitally modulating the signal by mplitude modulation.

In this OFDM system, since the transmission band is divided by a number of subcarriers, the band per subcarrier wave is narrowed and the modulation speed is reduced, but the total transmission speed is not different from the conventional modulation system. It has the feature of.

[0004] Further, the OFDM system has a feature that the symbol rate is reduced because many subcarriers are transmitted in parallel in a symbol unit called an OFDM symbol. Therefore, in the OFDM system, the time length of the multipath relative to the time length of the symbol can be shortened, and multipath interference is reduced. Also, in the OFDM method, data is allocated to a plurality of subcarriers, so that IFFT (Inverse Fast Fourier TIFF) for performing inverse Fourier transform at the time of modulation.
ransform) arithmetic circuit, F for performing Fourier transform at the time of demodulation
By using an FT (Fast Fourier Transform) operation circuit, a transmission / reception circuit can be configured.

[0005] From the above characteristics, the OFDM system has been widely studied for application to terrestrial digital broadcasting which is strongly affected by multipath interference. Such OF
As terrestrial digital broadcasting adopting the DM system, for example, ISDB-T (Integrated Services Digital Br
Oadcasting-Terrestrial) is being considered for adoption in Japan.

However, since the OFDM system is composed of a large number of subcarriers, the amplitude characteristic of the time waveform of the OFDM signal becomes more Gaussian (normal distribution) as the number of subcarriers increases. For this reason, the amplitude fluctuation and the maximum amplitude value are larger than those of the single carrier transmission method, so that it is necessary to set a wide dynamic range in each signal processing block including the transmission amplifier. Therefore,
When the backoff is set small in the transmission power amplifier, the maximum amplitude value exceeds the dynamic range,
Non-linear distortion due to power amplification occurs. When an OFDM signal is subjected to nonlinear distortion, orthogonality between subcarriers cannot be maintained, and the transmission characteristics rapidly decrease.

On the other hand, if the back-off is set large in the transmission power amplifier, the problem of non-linear distortion can be solved, but the power utilization efficiency is extremely reduced.

Therefore, in order to solve the above problems,
There has been proposed an OFDM communication apparatus and method for detecting a maximum value (maximum instantaneous power) of power at each signal point for each OFDM symbol and controlling power for each OFDM symbol according to the detected maximum instantaneous power. In this OFDM communication apparatus, when the maximum instantaneous power detected for each OFDM symbol exceeds the allowable range of the dynamic range, the maximum amplitude value is reduced by multiplying by a constant less than one. Hereinafter, this OFDM communication apparatus will be described with reference to FIG. 9 taking the transmitting side as an example.

An OFDM communication apparatus 10 shown in FIG. 9 includes an encoding processing block 101 and an OFDM modulation block 102
, A peak power detection block 103, a power reduction block 104, a signal extension block 105, a D / A conversion block 106, a frequency conversion block 107, a signal amplification block 108, and a transmission antenna block 109. I have.

The encoding processing block 101 receives transmission data as an information bit sequence from a transmission data input terminal. The encoding processing block 101 performs, for example, convolutional encoding processing for error correction, interleaving processing, mapping processing, OFDM frame configuration processing, and the like. The transmission data that has been subjected to error correction signal processing and the like is supplied to the OFDM modulation block 102.

An OFDM modulation block 102 performs an inverse Fourier transform on the input transmission data in OFDM symbol units at a time to obtain a baseband OFD in the time domain.
Generate an M signal. The OFDM signal is supplied to a peak power value detection block 103 and a power reduction block 104.

The peak power value detection block 103 calculates the power of the input baseband OFDM signal in the time domain for each signal point, and calculates the maximum instantaneous power for each OFDM symbol. Peak power value detection block 103
Outputs the maximum instantaneous power calculated for each OFDM symbol to the power reduction block 104.

The power reduction block 104 receives a baseband OFDM signal in the time domain and the maximum instantaneous power in OFDM symbol units. Power reduction block 104
Compares the dynamic range with the maximum instantaneous power for each OFDM symbol. When the maximum instantaneous power exceeds the dynamic range, the power reduction block 104 multiplies the OFDM symbol by a constant less than 1 so that the maximum instantaneous power becomes equal to the dynamic range. The power reduction block 104 performs such power controlled OFDM
The signal is supplied to the signal extension block 105.

The signal extension block 105 adds a guard interval to the OFDM signal and performs shaving processing for reducing discontinuity between symbols. The signal extension block 105 performs the OFD processing
The M signal is output to the D / A conversion block 106.

The D / A conversion block 106 receives an OFDM signal from the signal extension block. The D / A conversion block 106 converts a digital signal into an analog signal for the input OFDM signal. The OFDM signal converted to the analog signal is output to the frequency conversion block 1
07.

The frequency conversion block 107 converts the frequency of the input OFDM signal into a radio frequency band, and outputs the converted OFDM signal to the signal amplification block 108.

The signal amplification block 108 receives the input O
The FDM signal is amplified to a desired power for wireless communication. The signal amplification block 108 outputs the amplified OFDM signal to the transmission antenna block 109.

The transmitting antenna block 109 radiates the input OFDM signal into space as a broadcast wave.

[0019]

Since the conventional OFDM communication apparatus 10 can control the maximum instantaneous power in OFDM symbol units, it is possible to suppress nonlinear distortion due to exceeding the dynamic range. As a result, the back-off can be reduced, so that a decrease in power use efficiency can be prevented.

However, in the above-mentioned conventional OFDM communication apparatus 10, since the OFDM signal is multiplied by a constant of less than 1 for each OFDM symbol in order to adjust the maximum instantaneous power and dynamic range, the transmission power of the OFDM signal is attenuated, and However, there is a problem that the signal reproduction capability of the device is reduced.

Accordingly, the present invention has been devised to solve the above-described problem, and it is possible to reduce nonlinear distortion in units of symbols without changing the transmission power of a transmission signal itself. An object of the present invention is to provide an OFDM transmission apparatus and method. It is another object of the present invention to provide an OFDM receiving apparatus and method for removing a DC component from a received signal.

[0022]

In order to achieve the above object, an OFDM transmitting apparatus according to the present invention performs an inverse Fourier transform of an input signal in units of a symbol to obtain a baseband OFDM signal.
OFDM modulation means for generating a signal, DC component calculation means for calculating a DC component of the OFDM signal for each OFDM symbol, and OFD output from the OFDM modulation means
An adder for adding the DC component to the M signal for each OFDM symbol is provided.

This OFDM transmitting apparatus calculates a DC component of a baseband OFDM signal subjected to inverse Fourier transform for each symbol, and includes this in an OFDM symbol.

In order to achieve the above object, an OFDM transmission method according to the present invention generates an OFDM signal of a baseband by performing an inverse Fourier transform of an input signal in symbol units, and converts a DC component of the generated OFDM signal into an OFDM signal. The DC component is added to the OFDM signal calculated and generated for each symbol for each OFDM symbol.

In this OFDM transmission method, a DC component of a baseband OFDM signal subjected to inverse Fourier transform is calculated for each symbol, and this is included in the OFDM symbol.

In order to achieve the above object, an OFDM receiving apparatus according to the present invention comprises: a DC component calculating means for calculating a DC component of a received OFDM signal for each OFDM symbol;
Adding means for adding the DC component to the OFDM signal for each OFDM symbol; and Fourier transforming the OFDM signal output from the adding means in symbol units,
OFDM modulation means for generating an output signal in the frequency domain.

This OFDM receiver has the following features:
The DC component included in the received OFDM signal is calculated, and this is removed from each OFDM symbol.

To achieve the above object, an OFDM receiving method according to the present invention calculates a DC component of a received OFDM signal for each OFDM symbol, and converts the DC component into the OFDM signal.
The DC component is added for each OFDM symbol, and the OFDM signal to which the DC component is added is Fourier-transformed in symbol units to generate a frequency-domain output signal.

In this OFDM receiving method, for each symbol,
The DC component included in the received OFDM signal is calculated, and this is removed from each OFDM symbol.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an OFDM transmitting apparatus and method and an OFDM receiving apparatus and method according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an OFD according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of an OFDM transmission device 1 that calculates a DC component in units of M symbols and adds the calculated DC component to an OFDM signal that has been IFFT-converted.

The OFDM transmission apparatus 1 includes an encoding processing block 11, an OFDM modulation block 12, a DC component calculation block 13, a DC component application block 14, a signal extension block 15, a D / A conversion block 16, It comprises a frequency conversion block 17, a signal amplification block 18, and a transmission antenna block 19.

The encoding processing block 11 receives transmission data as an information bit sequence from a transmission data input terminal. The coding processing block 11 performs so-called error correction coding processing or the like in order to remove a code error occurring until a signal is received. For example, convolution coding processing, interleaving for spreading data, and the like are performed. processing,
It performs mapping processing, OFDM frame configuration processing, and the like.
Transmission data that has been subjected to error correction signal processing, etc.
It is supplied to the DM modulation block 12.

The OFDM modulation block 12 performs an inverse Fourier transform on the input transmission data in units of OFDM symbols, and obtains a baseband OFDM in the time domain.
Generate a signal. The generated OFDM signal is supplied to the DC component calculation block 13 and the DC component application block 14 for each symbol.

The DC component calculation block 13 performs an arithmetic process on the input baseband OFDM signal in the time domain, and calculates a DC component value required for each symbol. The calculation method will be described later in detail. The DC component calculation block 13 outputs the calculated DC component to the DC component application block 14.

The DC component application block 14 receives the baseband OFDM signal in the time domain and the DC component calculated for each symbol. This DC component application block 14 is an OFD modulated by the OFDM modulation block 12.
A time delay process is performed on the M signal to match the time with the DC component input from the DC component calculation block 13. The DC component application block 14 adds a DC component to the OFDM signal subjected to the time delay processing for each symbol. The DC component application block 14 supplies the OFDM signal to which the DC component has been added to the signal extension block 15.

The signal extension block 15 adds a guard interval to the OFDM signal and performs shaving processing to reduce discontinuity between symbols. The signal extension block 15 outputs the processed OFDM signal to the D / A conversion block 16.

The D / A conversion block 16 receives the OFDM signal from the signal extension block 15. The D / A conversion block 16 converts the input OFDM signal into
Converts digital signals to analog signals. The OFDM signal converted to an analog signal is output to the frequency conversion block 17.

The frequency conversion block 17 receives the input O
The frequency of the FDM signal is converted to a radio frequency band. The frequency conversion block 17 outputs the frequency-converted OFDM signal to the signal amplification block 18.

The signal amplification block 18 receives the input OF signal.
The DM signal is amplified to a desired power for wireless communication. The signal amplification block 18 sets a constant back-off, for example, to reduce nonlinear distortion. The signal amplification block 18 outputs the amplified OFDM signal to the transmission antenna block 19.

The transmission antenna block 19 radiates the input OFDM signal into space as a broadcast wave. The transmitting antenna in the transmitting antenna block 19 is, for example, a super turn style, a super gain, or a parabola antenna in satellite broadcasting.

Next, a specific example of the internal structure of the DC component application block 14 will be described with reference to FIG. As shown in FIG. 2, the DC component application block 14 includes a signal delay block 51 and an addition / subtraction block 52.

The signal delay block 51 receives a baseband OFDM signal in the time domain from the OFDM modulation block for each symbol. The signal delay block 51
The OFDM signal modulated by the DM modulation block 12 is subjected to a time delay process for adjusting the time to the DC component input from the DC component calculation block 13. In this time delay processing, for example, since the DC component must be calculated by detecting a signal for at least one symbol in the DC component application block 14, it is necessary to apply a time delay of at least one symbol. In this time delay process, for example, if the calculation time required in the DC component calculation block 13 is known, the calculation time may be configured as the delay amount. Further, in the time delay processing, the time delay amount may be configured based on, for example, information on the completion of the calculation notified from the DC component calculation block 13.

The addition / subtraction block 52 receives the OFDM signal subjected to the delay processing and the DC component calculated by the DC component calculation block 13. The addition / subtraction block 52
For each DM symbol, an input time-domain baseband OFDM signal and an input DC component are added.

Next, a method of calculating a DC component in the OFDM transmitting apparatus 1 will be described in detail with reference to the drawings.

FIG. 3 shows a first method of calculating a DC component in the OFDM transmitting apparatus 1. DC component calculation block 13
Is input with a signal that is OFDM-modulated in symbol units. For example, as shown in FIG. 3A, the DC component calculation block 13 receives the input OFDM for each OFDM symbol.
The signal is divided into an in-phase component (I-axis component) and a quadrature component (Q-axis component), and each signal point is plotted. The quadrature component calculation block 4 determines a maximum value and a minimum value for each of the in-phase component and the quadrature component. Next, the orthogonal component calculation block 4
The median value of the maximum value and the minimum value of the in-phase component and the median value of the maximum value and the minimum value of the quadrature component are calculated, and a value obtained by inverting the polarity of the calculated median value is defined as a DC component of each component. FIG.
(b) shows a specific example of the first calculation method. According to FIG. 3B, the maximum value of the in-phase component is +10, the minimum value is -14, and the maximum value of the quadrature component is +16, and the minimum value is -10. -2 and +3. When the central value of each component is inverted, the in-phase component becomes +2 and the quadrature component becomes -3.

As a result, in the addition / subtraction block 52, +2 is added to the in-phase component and -3 is added to the quadrature component of the OFDM signal for each OFDM symbol, so that the maximum value of the in-phase component is +12 and the minimum value is +12. Since the value is -12, the maximum value of the orthogonal component is +13, and the minimum value is -13, the maximum instantaneous power can be reduced.

Therefore, the OFDM transmitting apparatus 1 according to the present invention
Can add an optimum DC component for each OFDM symbol, so that the maximum instantaneous power can be reduced in symbol units and nonlinear distortion caused by exceeding the dynamic range can be suppressed. As a result, the back-off can be reduced, so that a decrease in power use efficiency can be prevented. Furthermore, since the OFDM transmitting apparatus 1 according to the present invention performs only the addition processing of the DC component on the OFDM signal itself, the above-described effect can be obtained without reducing the transmission power of the transmission signal.

FIG. 4 shows a second method of calculating the DC component in the OFDM transmitting apparatus 1. DC component calculation block 13
Is input with an OFDM-modulated signal for each OFDM symbol. The DC component calculation block 13 is, for example, as shown in FIG.
As shown in (a), the input OFDM signal is divided into an in-phase component and a quadrature component and plotted for each signal point. The DC component calculation block 13 determines the maximum value and the minimum value including both the in-phase component and the quadrature component of each signal point. Next, the DC component calculation block 13 calculates the median of the determined maximum value and minimum value. Next, the DC component calculation block 13
A value obtained by inverting the polarity of the calculated median value is defined as a DC component of an in-phase component and a quadrature component.

FIG. 4B shows a specific example of the second calculation method. According to FIG. 4B, the maximum value of the in-phase component is +10,
The minimum value is -14, the maximum value of the orthogonal components is +16, and the minimum value is -10, but the maximum value including both components is +16.
And the minimum value is −14. The median between the maximum value and the minimum value is +1. When the calculated median value +1 is inverted, the value becomes -1. Therefore, the DC component calculation block 1
The output of No. 3 is -1 for both the in-phase component and the quadrature component.

In the addition / subtraction block 52, for each symbol of the OFDM signal, -1 is used for the in-phase component and-for the quadrature component.
Since 1 is added, the maximum value of the in-phase component is +
9, the minimum value is -15, and the maximum value of the orthogonal component is +1.
5, the minimum value is -11. Thereby, the maximum value including both components becomes +15, and the minimum value becomes -15, so that the maximum instantaneous power can be reduced. Thereby, the back-off can be reduced, and the same effect as in the first calculation method can be obtained.

FIG. 5 shows a third method of calculating the DC component in the OFDM transmitting apparatus 1. DC component calculation block 13
Is input with an OFDM-modulated signal for each OFDM symbol. As shown in FIG. 5, the DC component calculation block 13 plots the input OFDM signal on the coordinates of the in-phase component and the quadrature component for each signal point. Next, the DC component calculation block 13 finds the origin of a circle that includes all the signal points and has the minimum radius on the coordinates. That is, such a circle includes all the signal points, and there are two or more signal points on the circumference. A value obtained by inverting the coordinates of the origin of such a circle is referred to as a DC component of each component.

The circle shown in FIG. 5 includes all of the signal points, and has a minimum radius, and the radius increases when the origin is moved in any direction. Since the in-phase component is -3 for the in-phase component and +2 for the quadrature component, when these polarities are inverted, the in-phase component becomes +3,
The orthogonal component is -2. Therefore, the DC component calculation block 1
In the output of No. 3, the in-phase component is +3 and the quadrature component is -2.

In the addition / subtraction block 52, for each signal point of the OFDM signal, +3 is used for the in-phase component and −2 is used for the quadrature component.
Is added. As a result, all the signal points move +3 in the I-axis direction and −2 in the Q-axis direction at the coordinates shown in FIG. At this time, the center of the circle shown in FIG. 5 also moves +3 in the I-axis direction and −2 in the Q-axis direction. Therefore, the maximum instantaneous power can be reduced, and the nonlinear distortion due to exceeding the dynamic range can be suppressed, so that the same effect as in the first embodiment can be obtained.

In addition, the DC component in the OFDM transmission apparatus 1 can be obtained by the following fourth calculation method.

In the fourth calculation method, the DC component calculation block 13 receives an OFDM-modulated signal in symbol units. The DC component calculation block 13 calculates the amplitude values of the in-phase component and the quadrature component for each signal point. Next, the DC component calculation block 13 performs a predetermined arithmetic process based on these amplitude values, thereby obtaining a DC component that minimizes the nonlinear distortion generated in the signal amplification block 18 for each component. Accordingly, even when the first calculation method for calculating the DC component from the median value cannot reduce the nonlinear distortion, for example, when only one point of the signal point is extremely A DC component that minimizes nonlinear distortion can be calculated from the whole. The exact formulas and the like for the arithmetic processing in the fourth calculation method are determined by the relationship with the signal amplification block 18. For example, a method of calculating a DC component by calculating an average value of all signal points is also included. It is.

In the fourth calculation method, the amplitude value of each signal point may be an amplitude value including both the in-phase component and the quadrature component.

Further, in the fourth calculation method, the OF component inputted in the DC component calculation block 13 in symbol units is used.
The present invention is also applicable to a case where a DM signal is divided into an in-phase component and a quadrature component and plotted on coordinates on a signal space diagram, and coordinates for minimizing nonlinear distortion are obtained from the entire plot.

By adding the DC component calculated by the fourth calculation method to the OFDM signal for each symbol, the maximum instantaneous power can be reduced. Thereby, nonlinear distortion can be suppressed, and back-off can be reduced, so that the same effect as in the first calculation method can be obtained.

FIG. 6 shows a configuration diagram of an OFDM receiver 3 for removing a DC component from a received signal as an embodiment of the present invention.

The OFDM receiver 3 includes a reception antenna block 31, a frequency conversion block 32, an A / D conversion block 33, a DC component calculation block 34, a DC component removal block 35, an OFDM demodulation block 36, And a correction processing block 37.

[0062] The receiving antenna block 31 receives an OFDM signal as a broadcast wave and outputs it to the frequency conversion block 32.

The frequency conversion block 32 converts the frequency of the input OFDM signal in the radio frequency band to the base band. The frequency conversion block 32 outputs the frequency-converted OFDM signal to the A / D conversion block 33.

The A / D conversion block 33 receives the OFDM signal from the frequency conversion block 32. This A / D
The conversion block 33 converts the input OFDM signal into
Converts analog signals to digital signals. The OFDM signal converted into a digital signal is output to a DC component calculation block 34 and a DC component removal block 35.

The DC component calculation block 34 performs an arithmetic process on the input OFDM signal, and calculates the value of the DC component included in the OFDM signal. This DC component also includes the DC component added in the OFDM transmitter 1. The method of calculating the DC component will be described later in detail. The DC component calculation block 34 outputs the calculated DC component to the DC component removal block 35.

The DC component removing block 35 outputs the OF signal converted to a digital signal in the A / D converting block 33.
The DM signal and the DC component calculated for each symbol are input.

The DC component removal block 35 performs a predetermined time delay process on the input OFDM signal in order to synchronize the time with the DC component input from the DC component calculation block 34. DC component removal block 35
Subtracts the DC component in symbol units from the time-delayed OFDM signal, and converts the subtracted OFDM signal into an ODM signal.
The signal is supplied to the FDM modulation block 36. The internal structure of the DC component removing block 35 is the same as that of the DC component applying block 15 in the OFDM transmitter 1 shown in FIG.

The OFDM modulation block 36 performs a Fourier transform on the baseband OFDM signal in the time domain collectively in units of symbols, and extracts and outputs data orthogonally modulated on each subcarrier. The signal output from the OFDM modulation block 36 is a Fourier-transformed frequency domain signal.

The error correction processing block 37 performs processing reverse to error correction processing and the like performed at the time of transmission,
The original information bit sequence data is restored. The error correction processing block outputs the restored received data to a received data output terminal.

Next, a method of calculating a DC component in the OFDM receiver 3 will be described in detail with reference to the drawings.

FIG. 7 shows a first calculation method of the DC component in the OFDM receiver 3. DC component calculation block 34
Is input with a signal that is OFDM-modulated in symbol units. The DC component calculation block 34 divides the input OFDM signal into an in-phase component and a quadrature component and plots each signal point as shown in FIG. 7A, for example. Next, the quadrature component calculation block 34 calculates an amplitude average value of each signal point for each of the in-phase component and the quadrature component, and sets a value obtained by inverting the polarity of the calculated amplitude average value as a DC component of each component.

FIG. 7B shows a specific example of the first calculation method. According to FIG. 7B, the amplitude average value of the in-phase component is +2.
And the average amplitude value of the orthogonal components is -4. That is, O
For each signal point of the FDM symbol, a DC component of +2 is added to the in-phase component and a DC component of -4 is added to the quadrature component. Therefore, in order to remove these, the polarity of the amplitude average value of each component is inverted, and O
It is added to each symbol of the FDM signal. In the specific example of FIG. 7B, the value obtained by inverting the polarity is −2 for the in-phase component and +4 for the quadrature component in the specific example of FIG. 7B. As a result, the added DC component can be removed.

FIG. 8 shows a second method of calculating the DC component in the OFDM receiver 3. DC component calculation block 34
Is input with a signal that is OFDM-modulated in symbol units. The DC component calculation block 34 divides the input OFDM signal into an in-phase component and a quadrature component and plots each signal point, for example, as shown in FIG. Next, the quadrature component calculation block 34 calculates an average amplitude value including both the in-phase component and the quadrature component, and uses the values obtained by inverting the polarities of the calculated average amplitude values as DC components of the respective components.

FIG. 8B shows a specific example of the second calculation method. According to FIG. 8B, since the average amplitude value including both the in-phase component and the quadrature component is −1, the value obtained by inverting the polarity of the average amplitude value is +1. Therefore, the in-phase component of the DC component is -1 and the quadrature component is -1.

Thus, similarly to the first calculation method, the added DC component can be removed, so that the same effect as in the first calculation method can be obtained.

[0076]

As described in detail above, the OFDM transmitting apparatus according to the present invention can add an optimal DC component for each OFDM symbol, thereby reducing non-linear distortion and preventing a decrease in transmission power. can do.

The OFDM transmission method according to the present invention
Since an optimal DC component can be added for each DM symbol, nonlinear distortion can be reduced and a decrease in transmission power can be prevented.

The OFDM receiving apparatus according to the present invention
DC components added for each DM symbol can be removed.

The OFDM receiving method according to the present invention
DC components added for each DM symbol can be removed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a block configuration of an OFDM transmitting apparatus to which the present invention has been applied.

FIG. 2 is a diagram showing an example of an internal configuration of a DC component application block 15;

FIG. 3 is a diagram illustrating a first calculation method of a DC component in the OFDM transmission device.

FIG. 4 is a diagram illustrating a second method of calculating a DC component in the OFDM transmitting apparatus.

FIG. 5 is a diagram illustrating a third method of calculating a DC component in the OFDM transmitting apparatus.

FIG. 6 is a diagram illustrating an example of a block configuration of an OFDM receiving apparatus to which the present invention has been applied.

FIG. 7 is a diagram illustrating a first method of calculating a DC component in the OFDM receiver.

FIG. 8 is a diagram illustrating a second method of calculating a DC component in the OFDM receiver.

FIG. 9 shows an OFD that detects a maximum instantaneous power and controls power for each OFDM symbol according to the detected maximum instantaneous power.
FIG. 3 is a diagram illustrating an example of a block configuration of an M communication device.

[Explanation of symbols]

1 OFDM transmitter, 11 coding processing block, 1
2 OFDM modulation block, 13 DC component calculation block, 14 DC component application block, 15 signal extension block, 16 D / A conversion block, 17 frequency conversion block, 18 signal amplification block, 19 transmission antenna block

Claims (18)

[Claims] 1. An OFDM transmitting apparatus for transmitting an orthogonal frequency division multiplexing (OFDM) signal, comprising: an inverse Fourier transform of an input signal in symbol units to generate a baseband OFDM signal; DC component calculating means for calculating a component for each OFDM symbol; and an OFDM signal output from the OFDM modulating means,
An OFDM transmission apparatus comprising: an adding unit that adds the DC component for each OFDM symbol. 2. The method according to claim 1, wherein the direct current component calculating means is configured to output the OFDM signal.
2. The OFD according to claim 1, wherein the DC component is calculated based on the maximum value and the minimum value of the in-phase component of each signal point of the symbol and the maximum value and the minimum value of the quadrature component.
M transmitter. 3. The direct current component calculating means according to claim 1,
2. The OFDM transmission apparatus according to claim 1, wherein the DC component is calculated based on a maximum value and a minimum value including both an in-phase component and a quadrature component of each signal point of the symbol. 4. The DC component calculating means includes all the signal points of the OFDM symbol shown on the signal space diagram and based on the coordinates of the center point of a circle having a minimum radius. 2. The OFDM transmitting apparatus according to claim 1, wherein the OFDM transmission apparatus calculates: 5. The OFD output from the adding means.
Signal amplification means for amplifying the M signal, wherein the DC component calculation means minimizes nonlinear distortion generated by the signal amplification means based on the amplitude values of the in-phase component and the quadrature component of each signal point of the OFDM symbol. 2. The OF according to claim 1, wherein the DC component is calculated.
DM transmitter. 6. The OFD output from the adding means.
A signal amplifying means for amplifying the M signal; wherein the DC component calculating means is provided by the signal amplifying means based on a distance between each signal point of the OFDM symbol shown on the signal space diagram and the origin of the signal space diagram. 2. The OFDM transmission apparatus according to claim 1, wherein a DC component that minimizes the generated nonlinear distortion is calculated. 7. An OFDM transmission method for transmitting an orthogonal frequency division multiplexing (OFDM) signal, wherein an inverse Fourier transform of an input signal is performed in a symbol unit to generate a baseband OFDM signal, and a DC component of the generated OFDM signal is calculated. The DC component is calculated for each OFDM symbol, and the generated DC signal is added to each OFDM symbol.
An OFDM transmission method, wherein the addition is performed for each DM symbol. 8. The DC component according to claim 7, wherein the DC component is calculated based on a maximum value and a minimum value in an in-phase component and a maximum value and a minimum value in a quadrature component of each signal point of the OFDM symbol. OFDM transmission method. 9. The DC component is calculated based on a maximum value and a minimum value including both an in-phase component and a quadrature component of each signal point of the OFDM symbol.
The described OFDM transmission method. 10. The DC component is calculated based on coordinates of a center point of a circle including all signal points of the OFDM symbol shown on a signal space diagram and having a minimum radius. The OFD according to claim 7, wherein
M transmission method. 11. An OFDM transmitting apparatus provided with a signal amplifying unit for amplifying a signal to which a DC component has been added.
In the FDM transmission method, a DC component that minimizes nonlinear distortion generated in the signal amplifying unit is calculated based on amplitude values of an in-phase component and a quadrature component of each signal point of the OFDM symbol. Item 8. The OFDM transmission method according to Item 7. 12. An OFDM transmitting apparatus provided with a signal amplifier for amplifying a signal to which a DC component has been added.
In the FDM transmission method, based on the distance between each signal point of the OFDM symbol shown on the signal space diagram and the origin of the signal space diagram, a DC component that minimizes nonlinear distortion generated by the signal amplifying means is determined. The OFDM transmission method according to claim 7, wherein the calculation is performed. 13. An OFDM receiving apparatus for receiving an orthogonal frequency division multiplexing (OFDM) signal, a DC component calculating means for calculating a DC component of the received OFDM signal for each OFDM symbol, and the DC component in the OFDM signal. , An adding means for adding each OFDM symbol, and an OFDM modulating means for performing a Fourier transform of the OFDM signal output from the adding means on a symbol basis to generate an output signal in the frequency domain.
M receiving device. 14. The direct current component calculating means, wherein the OFD
Average amplitude value of the in-phase component at each signal point of M symbols,
14. The OFDM receiving apparatus according to claim 13, wherein the DC component is calculated based on an amplitude average value of orthogonal components. 15. The direct current component calculating means,
14. The OFDM receiver according to claim 13, wherein the DC component is calculated based on an amplitude average value including both an in-phase component and a quadrature component at each signal point of M symbols. 16. An OFDM receiving method for receiving an orthogonal frequency division multiplexing (OFDM) signal, wherein a DC component of the received OFDM signal is calculated for each OFDM symbol, and the DC component is added to the OFDM signal for each OFDM symbol. An OFDM signal to which the DC component has been added is subjected to Fourier transform in symbol units to generate a frequency domain output signal. 17. The OFDM receiving method according to claim 16, wherein the DC component is calculated based on an average amplitude value of an in-phase component and an average amplitude value of a quadrature component of each signal point of the OFDM symbol. 18. Based on an amplitude average value including both an in-phase component and a quadrature component of each signal point of the OFDM symbol,
17. The OFDM receiving method according to claim 16, wherein said DC component is calculated.