JP2002152169A - Device and method for receiving orthogonal frequency- division multiplex signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably equalize a received signal by exactly specifying the characteristics of a transmission line. SOLUTION: A division processing part 25 specifies the variation quantity of transmission characteristic data to a subcarrier transmitting an SP signal by performing complex division to a level value, which shows the data level of the transmission line characteristic data, notified from a first level detecting part 23 by a level value, which shows the data level of the transmission characteristic data, notified from a second level detecting part 24. On the basis of the variation quantity of the transmission line characteristic data notified from the dividing processing part 25, a characteristic data correcting processing part 26 corrects the transmission line characteristic data received from a subcarrier direction interpolation processing part 22. While using the transmission line characteristic data corrected by the characteristic data correcting processing part 26, an equalizing operating processing part 27 equalizes the received signal by performing complex division or the like to received signal data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal frequency division multiplexing signal receiving apparatus for receiving signals subjected to orthogonal frequency division multiplexing and decoding transmission data, and more particularly to an apparatus for appropriately equalizing a received signal. The present invention relates to an orthogonal frequency division multiplexed signal receiving device capable of decoding transmission data.

[0002]

2. Description of the Related Art Orthogonal frequency division multiplexing (OFDM) is one of the digital signal transmission systems.
The ency division multiplex method is known. Some orthogonal frequency division multiplexing systems transmit data by inserting a pilot signal generated at a predetermined amplitude, phase, and timing into a predetermined subcarrier. For example,
DVB-T (Digital) using orthogonal frequency division multiplexing
Video Broadcasting-Terrestrial) or ISDB-T (In
integrated Services Digital Broadcasting-Terrestria
In the system for synchronous modulation in l), the SP (Scatter
A pilot signal called an ed Pilot (dispersed pilot) signal is used.

Here, for example, a receiving apparatus that is applied to a DVB-T system and receives an orthogonal frequency division multiplexed signal and decodes transmission data by using an equalizer is first configured based on the received signal data. , Transmission path characteristics for the subcarriers that have transmitted the SP signal. Next, the receiving apparatus filters the data indicating the channel characteristics in the symbol direction (time direction) and the subcarrier direction (frequency direction) using a symbol filter, a subcarrier filter, and the like. As a result, the transmission path characteristics specified only for the subcarriers transmitting the SP signal are interpolated and interpolated to obtain transmission path characteristic data indicating the transmission path characteristics for all the subcarriers.

[0004] The receiving apparatus divides the received signal data by using the transmission path characteristic data obtained in this manner, and thereby equalizes the received signal data corresponding to the influence of the transmission path (eg, fading). , And the transmission data can be decoded by demapping or the like.

[0005]

In the above prior art, transmission path characteristic data specified for a subcarrier on which an SP signal is transmitted is usually interpolated in the symbol direction (time direction) using a symbol filter. After interpolation, LP
Interpolation is performed by interpolating in the subcarrier direction (frequency direction) by a subcarrier filter composed of F (Low Pass Filter).

At this time, it is difficult to make the LPF used as a subcarrier filter have ideal frequency characteristics. That is, it is ideal that the LPF has a step-like low-pass characteristic with a predetermined frequency as a high-frequency cutoff frequency. However, in reality, it is difficult to obtain such characteristics, and ripples (pulsations) and a finite inclination often occur in the frequency characteristics. For this reason, distortion occurs in the transmission path characteristic data, and it may not be possible to appropriately equalize the received signal data.

The present invention has been made in view of the above situation, and provides an orthogonal frequency division multiplexed signal receiving apparatus capable of accurately specifying characteristics of a transmission path and appropriately equalizing a received signal. The purpose is to:

[0008]

In order to achieve the above object, an orthogonal frequency division multiplex signal receiving apparatus according to a first aspect of the present invention is based on a distributed pilot signal inserted in a predetermined subcarrier and transmitted. Determining the characteristics of the transmission path, and decoding the transmission data after equalizing the received signal data according to the transmission path characteristics, specifying the transmission path characteristics for the subcarriers that transmitted the distributed pilot signal, Along with executing a filtering process for obtaining data indicating transmission channel characteristics corresponding to all subcarriers based on the data indicating the specified transmission channel characteristics, detecting a change amount of a data level before and after the filtering process, Data indicating transmission path characteristics is corrected based on the detection result, and received signal data is equalized using the corrected data. The features.

According to the present invention, the amount of change in the data level before and after the filtering process for obtaining the data indicating the transmission path characteristics corresponding to all the subcarriers is detected, and the data indicating the transmission path characteristics is corrected. be able to. This makes it possible to correct data distortion due to the filtering process, accurately specify the characteristics of the transmission path, and appropriately equalize the received signal.

[0010] An orthogonal frequency division multiplexed signal receiving apparatus according to a second aspect of the present invention receives received signal data indicating an orthogonal frequency division multiplexed signal in which a scattered pilot signal is inserted into a predetermined subcarrier, and transmits transmission data. Fourier transform means for performing Fourier transform on the input received signal data, based on the received signal data Fourier transformed by the Fourier transform means. , A first interpolating means for interpolating the data indicating the transmission path characteristics specified by the characteristic specifying means in the symbol direction, and a transmission interpolated in the symbol direction by the first interpolating means. A second interpolating means for interpolating the data indicating the road characteristics in the subcarrier direction and the first interpolating means. A first detector for detecting a data level of data indicating transmission path characteristics interpolated in the vol direction, and a data level of data indicating transmission path characteristics interpolated in the subcarrier direction by the second interpolation means And a characteristic correction unit for correcting data indicating transmission path characteristics interpolated in the subcarrier direction by the second interpolation unit based on the detection results obtained by the first and second detection units. Signal equalizing means for equalizing received signal data Fourier-transformed by the Fourier transform means, using data indicating transmission path characteristics corrected by the characteristic correcting means, and equalization by the signal equalizing means And demapping means for decoding transmission data from the received signal data thus obtained.

According to the present invention, the data level before and after the second interpolation means interpolates the data indicating the transmission path characteristics in the subcarrier direction is detected by using the first and second detection means. The characteristic correcting means corrects the data interpolated by the second interpolating means based on the detection results by the first and second detecting means, thereby causing the second interpolating means to interpolate the data. Data distortion can be corrected. This makes it possible to accurately specify the characteristics of the transmission path and appropriately equalize the received signal.

More specifically, the first detecting means, among the data interpolated in the symbol direction by the first interpolating means, data of data indicating a transmission path characteristic with respect to a subcarrier transmitting a scattered pilot signal. Level, and the second detector detects a data level of data indicating transmission path characteristics with respect to the subcarrier transmitting the scattered pilot signal among the data interpolated in the subcarrier direction by the second interpolator. It is desirable to detect.

Further, the characteristic correcting means divides a level value indicating the data level detected by the first detecting means by a level value indicating the data level detected by the second detecting means. Means for obtaining corrected data by averaging the results of division by said division processing means, and multiplying data showing transmission path characteristics corresponding to all subcarriers by fixed correction data to obtain transmission data. It is desirable to include a product processing means for correcting data indicating characteristics.

An orthogonal frequency division multiplexed signal receiving apparatus according to a third aspect of the present invention receives received signal data indicating an orthogonal frequency division multiplexed signal in which a scattered pilot signal is inserted into a predetermined subcarrier, and transmits transmission data. Fourier transform means for performing Fourier transform on the input received signal data, based on the received signal data Fourier transformed by the Fourier transform means. , A first interpolating means for interpolating the data indicating the transmission path characteristics specified by the characteristic specifying means in the symbol direction, and a transmission interpolated in the symbol direction by the first interpolating means. Second interpolating means for interpolating data indicating a road characteristic in the subcarrier direction, and the characteristic specifying means First detecting means for detecting the data level of the data indicating the obtained transmission path characteristic, and second detecting means for detecting the data level of the data indicating the transmission path characteristic interpolated in the subcarrier direction by the second interpolation means. Detection means; characteristic correction means for correcting data indicating transmission path characteristics interpolated in the subcarrier direction by the second interpolation means based on the detection results by the first and second detection means; A signal equalizer for equalizing the received signal data Fourier-transformed by the Fourier transformer using data indicating the transmission path characteristic corrected by the corrector, and a received signal equalized by the signal equalizer. And demapping means for decoding transmission data from data.

According to the present invention, the data levels before and after the first and second interpolation means interpolate the data indicating the transmission path characteristics are detected using the first and second detection means. The characteristic correction means corrects the data interpolated by the second interpolation means based on the detection results by the first and second detection means, so that the first and second interpolation means interpolate the data. Can be corrected. This makes it possible to accurately specify the characteristics of the transmission path and appropriately equalize the received signal.

An orthogonal frequency division multiplexed signal receiving method according to a fourth aspect of the present invention decodes transmission data from received signal data indicating an orthogonal frequency division multiplexed signal in which a scattered pilot signal is inserted into a predetermined subcarrier. A Fourier transform step of performing a Fourier transform on the received signal data, and specifying a transmission path characteristic for a subcarrier transmitting the distributed pilot signal based on the received signal data subjected to the Fourier transform in the Fourier transform step. A characteristic specifying step, a first interpolation step of interpolating in a symbol direction data indicating the transmission path characteristic specified in the characteristic specifying step, and a transmission path characteristic interpolated in the symbol direction in the first interpolation step. The data shown
A second interpolation step for interpolating in the subcarrier direction, a first detection step for detecting the data level of the data interpolated in the symbol direction in the first interpolation step, and a subcarrier in the second interpolation step. A second detection step of detecting the data level of the data interpolated in the direction, and a transmission path interpolated in the subcarrier direction in the second interpolation step based on the detection results in the first and second detection steps. A characteristic correction step of correcting data indicating characteristics, a signal equalization step of equalizing received signal data Fourier-transformed in the Fourier transformation step using the data corrected in the characteristic correction step, And a demapping step of decoding transmission data from the received signal data equalized in the equalization step. .

An orthogonal frequency division multiplexed signal receiving method according to a fifth aspect of the present invention decodes transmission data from received signal data indicating an orthogonal frequency division multiplexed signal in which a scattered pilot signal is inserted into a predetermined subcarrier. A Fourier transform step of performing a Fourier transform on the received signal data, and specifying a transmission path characteristic for a subcarrier transmitting the distributed pilot signal based on the received signal data subjected to the Fourier transform in the Fourier transform step. A characteristic specifying step, a first interpolation step of interpolating in a symbol direction data indicating the transmission path characteristic specified in the characteristic specifying step, and a transmission path characteristic interpolated in the symbol direction in the first interpolation step. The data shown
A second interpolation step for interpolating in the subcarrier direction, a first detection step for detecting a data level of data indicating the transmission path characteristics specified in the characteristic specification step, and a subcarrier in the second interpolation step. A second detection step of detecting the data level of the data interpolated in the direction, and a transmission path interpolated in the subcarrier direction in the second interpolation step based on the detection results in the first and second detection steps. A characteristic correction step of correcting data indicating characteristics, a signal equalization step of equalizing received signal data Fourier-transformed in the Fourier transformation step using the data corrected in the characteristic correction step, And a demapping step of decoding transmission data from the received signal data equalized in the equalization step. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an orthogonal frequency division multiplex signal receiving apparatus 100 according to an embodiment of the present invention will be described in detail with reference to the drawings.

An orthogonal frequency division multiplexed signal receiving apparatus 100 according to an embodiment of the present invention receives baseband received signal data obtained by, for example, detection by a quadrature detector and receives transmission data sent from a transmitting side. Decrypt (restore). Here, the signal detected by the quadrature detector is, for example, after being received by an antenna and down-converted,
An IF (Intermediate Frequency) signal digitized by an ADC (Analog / Digital Converter).

This orthogonal frequency division multiplex signal receiving apparatus 10
The received signal data input to 0 is digitized data of an orthogonal frequency division multiplexed signal that has been subjected to orthogonal frequency division multiplexing on the transmission side and transmitted using a number of subcarriers that are orthogonal to each other in a symbol period. .

The orthogonal frequency division multiplexed signal includes a predetermined subcarrier having a period of 4 symbols in the symbol direction (time direction) and 12 subcarriers in the subcarrier direction (frequency direction). , An SP (scattered pilot) signal having a known amplitude and phase is inserted.

In order to receive such an orthogonal frequency division multiplexed signal and decode the transmission data, the orthogonal frequency division multiplexed signal receiving apparatus 100 uses an FFT as shown in FIG.
(Fast Fourier Transform) Circuit 1
0, an equalization processing unit 11, and a demapper circuit 12.

The FFT circuit 10 Fourier-transforms the received signal data to convert time-series data on the time axis into frequency component data on the frequency axis. The FFT circuit 10 converts the received signal data into frequency component data. Is sent to the equalization processing unit 11.

The equalization processing section 11 performs equalization processing of the received signal data, and corrects the received signal data that has deteriorated due to the influence of the transmission path (for example, fading). As shown in FIG. 2, the equalization processing unit 11 includes a characteristic data calculation processing unit 20 and a symbol direction interpolation processing unit 2.
1, a subcarrier direction interpolation processing unit 22, first and second level detection units 23 and 24, a division processing unit 25, a characteristic data correction processing unit 26, and an equalization calculation processing unit 27. I have.

The characteristic data calculation processing unit 20, for example,
By extracting the subcarrier transmitting the SP signal from the received signal data Fourier-transformed by the FT circuit 10, and performing complex division with data indicating the reference SP signal generated at a predetermined timing, the characteristics of the transmission path are obtained. Is generated. At this time, the characteristic data calculation processing unit 20 obtains, by complex division, transmission line characteristic data indicating transmission line characteristics in the subcarrier that transmitted the SP signal, and inserts zero as transmission line characteristic data for the other subcarriers. .

The symbol direction interpolation processing section 21, for example,
The transmission path characteristic data, which is configured using an IR (Finite Impulse Response) filter or an IIR (Infinite Impulse Response) filter, and is specified by the characteristic data calculation processing unit 20 for the subcarrier that transmitted the SP signal, is represented by a symbol. Interpolate by interpolating in the direction (time direction).

The subcarrier direction interpolation processing section 22 is composed of, for example, an LPF (Low Pass Filter) or the like.
The transmission line characteristic data for all subcarriers is generated by interpolating the transmission line characteristic data interpolated in the subcarrier direction (frequency direction).

The first level detection section 23 is a data level of the transmission path characteristic data corresponding to the subcarrier transmitting the SP signal, among the transmission path characteristic data interpolated in the symbol direction (time direction) by the symbol direction interpolation processing section 21. Is to be detected.

The second level detecting section 24 is, of the transmission line specifying data interpolated in the subcarrier direction (frequency direction) by the subcarrier direction interpolation processing section 22, the one corresponding to the subcarrier transmitting the SP signal. This is for detecting a data level.

The division processing section 25 generates correction data for correcting the transmission path characteristic data based on the data level of the transmission path characteristic data detected by the first and second level detection sections 23 and 24. belongs to. That is, the division processing unit 25 converts the level value indicating the data level detected by the first level detection unit 23 into the second level detection unit 24
To generate corrected data by dividing by the level value indicating the detected data level.

The characteristic data correction processing unit 26 is composed of, for example, a multiplier or the like, and the division processing unit 25 generates transmission path characteristic data obtained for all subcarriers by the subcarrier direction interpolation processing unit 22. This is for correcting using the correction data. For example, the characteristic data correction processing unit 26 averages the correction data generated by the division processing unit 25 based on the data level of the transmission path characteristic data corresponding to the subcarrier that transmitted the SP signal, and corresponds to all subcarriers. The level change of the transmission path characteristic data is corrected by multiplying the transmission path characteristic data by fixed correction data.

The equalization operation processing section 27 is composed of a numerical operation circuit and the like, and performs complex division of the received signal data received from the FFT circuit 10 using the transmission path characteristic data corrected by the characteristic data correction processing section 26. This is for equalizing the received signal data by executing a complex operation such as

The demapper circuit 12 shown in FIG.
An OM (Read Only Memory) or the like for executing a demapping process of decoding transmission data from received signal data equalized by the equalization processing unit 11 based on a symbol arrangement diagram on a complex plane. It is. That is,
The demapper circuit 12 is, for example, 64QAM (Quadrature A).
The transmission data is decoded from the in-phase component and the quadrature component of the reception signal data modulated by a multi-level modulation method such as amplitude modulation based on a correspondence between a predetermined coordinate value on the complex plane and the transmission data. Demapper circuit 1
Reference numeral 2 outputs the decoded transmission data to a deinterleave circuit or the like, and performs processing on the transmission data.

The operation of the orthogonal frequency division multiplex signal receiving apparatus 100 according to the embodiment of the present invention will be described below.
When the orthogonal frequency division multiplexed signal receiving apparatus 100 decodes the transmission data, first, the FFT circuit 10 receives the received signal data obtained by the detection of the orthogonal detector, performs a Fourier transform, and performs frequency conversion from the time series data. Convert to component data. The FFT circuit 10 sends the received signal data as the frequency component data to the equalization processing unit 11.

Next, the equalization processing section 11
A process for equalizing the received signal data received from is performed. FIG. 3 is a diagram illustrating a configuration of an orthogonal frequency division multiplexed signal indicated by received signal data input to the equalization processing unit 11.

In FIG. 3, the subcarriers with the suffix SP are subcarriers into which the SP signal is inserted on the transmitting side. That is, the SP signal is inserted into a predetermined subcarrier having a period of 4 symbols in the symbol direction (time direction) and a period of 12 symbols in the subcarrier direction (frequency direction) and transmitted.

The characteristic data calculation processing unit 20, for example,
The subcarrier transmitting the P signal (subscript SP in FIG. 3)
) Is complex-divided by a reference SP signal generated at a known amplitude, phase, and timing on the receiving side. As a result, transmission path characteristics corresponding to the subcarrier that has transmitted the SP signal can be obtained.

The characteristic data calculation processing section 20 sends to the symbol direction interpolation processing section 21 transmission path characteristic data indicating the transmission path characteristics obtained for the subcarriers that transmitted the SP signal. At this time, the characteristic data calculation processing unit 20 inserts zero as transmission path characteristic data for subcarriers other than the subcarrier that transmitted the SP signal, and sends the result to the symbol direction interpolation processing unit 21.

The symbol direction interpolation processing unit 21 performs a filtering process for interpolating the transmission path characteristic data received from the characteristic data calculation processing unit 20 in the symbol direction (time direction), and marked with * in FIG. Find the transmission path characteristics for the subcarrier. Symbol direction interpolation processing unit 2
1 sends the transmission path characteristic data interpolated in the symbol direction (time direction) to the subcarrier direction interpolation processing unit 22.

Here, the first level detection section 23 detects the data level of the transmission path characteristic data sent from the symbol direction interpolation processing section 21 to the subcarrier direction interpolation processing section 22, and notifies the division processing section 25. .

The sub-carrier direction interpolation processing unit 22 executes a filtering process for interpolating the transmission path characteristic data received from the symbol direction interpolation processing unit 21 in the sub-carrier direction (frequency direction). A transmission path characteristic for the attached subcarrier is obtained. The subcarrier direction interpolation processing unit 22 sends the transmission line characteristic data interpolated in the subcarrier direction (frequency direction) to the characteristic data correction processing unit 26.

Here, the second level detection unit 24 detects the data level of the transmission path characteristic data sent from the subcarrier direction interpolation processing unit 22 to the characteristic data correction processing unit 26, and notifies the division processing unit 25. .

Since the subcarrier direction interpolation processing section 22 only interpolates the transmission path characteristic data in the subcarrier direction (frequency direction), the transmission path characteristic data for the subcarrier that has transmitted the SP signal before and after the filtering processing is performed. Ideally, it should not change. However, actually, when the transmission path characteristic data is interpolated in the subcarrier direction, due to the filtering process performed by the subcarrier direction interpolation processing unit 22, the transmission path characteristic data for the subcarrier that transmitted the SP signal is Data levels may change.

Therefore, the division processing unit 25 determines the data level of the transmission line characteristic data detected by the first level detection unit 23 and the data level of the transmission line characteristic data detected by the second level detection unit 24. Then, the amount of variation of the transmission path characteristic data with respect to the subcarrier that has transmitted the SP signal is specified. That is, the division processing unit 25 changes the level value indicating the data level of the transmission line characteristic data notified from the first level detection unit 23 to the data level of the transmission line characteristic data notified from the second level detection unit 24. By performing complex division by a level value indicating the amount of change in transmission path characteristic data with respect to the subcarrier that has transmitted the SP signal. The division processing unit 25 calculates the amount of change in the specified transmission path characteristic data,
The characteristic data correction processing unit 26 is notified as correction data.

The characteristic data correction processing section 26 corrects the transmission path characteristic data received from the subcarrier direction interpolation processing section 22 based on the variation of the transmission path characteristic data notified from the division processing section 25. That is, for example, the characteristic data correction processing unit 26 averages the correction data received from the division processing unit 25 and multiplies all the transmission line characteristic data by a fixed correction data, thereby obtaining the transmission path characteristic data. Compensate for level changes. The characteristic data correction processing unit 26
The corrected transmission path characteristic data is sent to the equalization calculation processing section 27.

Using the transmission path characteristic data received from the characteristic data correction processing section 26,
The received signal data received from the circuit 10 is equalized by performing complex division or the like. Equalization operation processing unit 27
Converts the equalized received signal data into a demapper circuit 1.
Send to 2.

The demapper circuit 12 decodes the transmission data using the reception signal data subjected to the equalization processing by the equalization processing section 11, and outputs it to a circuit for processing the transmission data such as a deinterleave circuit.

As described above, according to the present invention,
The data level of the transmission path characteristic data sent from the symbol direction interpolation processing section 21 to the subcarrier direction interpolation processing section 22 and the data level of the transmission path characteristic data sent from the subcarrier direction interpolation processing section 22 to the characteristic data correction processing section 26 And detect. Then, the level change of the transmission path characteristic data is corrected based on the detected data level. In other words, by detecting the data level of the transmission path characteristic data before and after the interpolation in the subcarrier direction (frequency direction) by the subcarrier direction interpolation processing unit 22, the filtering is performed by the subcarrier direction interpolation processing unit 22. The distortion of the transmission path characteristic data can be corrected. As a result, the characteristics of the transmission path can be accurately specified, and the received signal can be appropriately equalized.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, in the above embodiment, the first level detection unit 23 is configured to switch from the symbol direction interpolation processing unit 21 to the subcarrier direction interpolation processing unit 22.
However, the present invention is not limited to this. That is, for example, the first level detection unit 23 may detect the data level of the transmission path characteristic data sent from the characteristic data calculation processing unit 20 to the symbol direction interpolation processing unit 21 as shown in FIG. Good. This allows
The distortion including the level change of the transmission path characteristic data resulting from the filtering processing executed by the symbol direction interpolation processing unit 21 can be detected, and the distortion of the transmission path characteristic data can be corrected.

[0050]

As described above, according to the present invention, it is possible to detect a level change caused by a filtering process for interpolating data indicating characteristics of a transmission line and correct data distortion. In addition, it is possible to accurately specify the characteristics of the transmission path and appropriately equalize the received signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an orthogonal frequency division multiplexed signal receiving apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an equalization processing unit.

FIG. 3 is a diagram illustrating a configuration of an orthogonal frequency division multiplex signal.

FIG. 4 is a diagram showing a modification of the orthogonal frequency division multiplexed signal receiving apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 FFT circuit 11 Equalization processing unit 12 Demapper circuit 20 Characteristic data calculation processing unit 21 Symbol direction interpolation processing unit 22 Subcarrier direction interpolation processing unit 23, 24 Level detection unit 25 Division processing unit 26 Characteristic data correction processing unit 27 Equalization operation Processing unit

Claims (7)

[Claims] 1. A transmission path characteristic is obtained based on a scattered pilot signal inserted in a predetermined subcarrier and transmitted,
An orthogonal frequency division multiplexing signal receiving apparatus for decoding transmission data after equalizing received signal data in accordance with transmission path characteristics, and specifying and specifying transmission path characteristics for subcarriers transmitting a distributed pilot signal. A filtering process for obtaining data indicating transmission path characteristics corresponding to all subcarriers is performed based on data indicating transmission path characteristics, and a change amount of a data level before and after the filtering processing is detected, and a detection result is obtained. , And corrects received signal data using the corrected data, thereby obtaining an orthogonal frequency division multiplexed signal receiving apparatus. 2. An orthogonal frequency division multiplex signal receiving apparatus for receiving received signal data indicating an orthogonal frequency division multiplex signal in which a scattered pilot signal is inserted into a predetermined subcarrier and decoding transmission data. Fourier transform means for Fourier transforming the received signal data; Characteristic specifying means for specifying a channel characteristic for a subcarrier that has transmitted a scattered pilot signal based on the received signal data Fourier-transformed by the Fourier transform means; First interpolating means for interpolating in the symbol direction data indicating the channel characteristics specified by the specifying means; and data indicating the channel characteristics interpolated in the symbol direction by the first interpolating means in the subcarrier direction. A second interpolating means for interpolating the signal in the transmission direction, First detecting means for detecting a data level of data indicating the following; second detecting means for detecting a data level of data indicating transmission path characteristics interpolated in the subcarrier direction by the second interpolating means; A characteristic correction unit configured to correct data indicating a channel characteristic interpolated in the subcarrier direction by the second interpolation unit based on a detection result obtained by the first and second detection units; Signal equalizing means for equalizing the received signal data Fourier-transformed by the Fourier transform means, using data indicating the transmission path characteristics, and transmitting data from the received signal data equalized by the signal equalizing means. An orthogonal frequency division multiplexed signal receiving apparatus, comprising: a demapping unit for decoding. 3. The first detecting means detects a data level of data indicating a transmission path characteristic for a subcarrier transmitting a scattered pilot signal among data interpolated in the symbol direction by the first interpolating means. Wherein the second detecting means detects a data level of data indicating a transmission path characteristic for the subcarrier transmitting the scattered pilot signal among the data interpolated in the subcarrier direction by the second interpolating means, The orthogonal frequency division multiplexed signal receiving apparatus according to claim 2, wherein: 4. A dividing process for dividing a level value indicating a data level detected by the first detecting means by a level value indicating a data level detected by the second detecting means. Means for obtaining corrected data by averaging the results of division by said division processing means, and multiplying data showing transmission path characteristics corresponding to all subcarriers with fixed correction data to obtain a transmission path. The orthogonal frequency division multiplexed signal receiving apparatus according to claim 2, further comprising: a product processing unit that corrects data indicating characteristics. 5. An orthogonal frequency division multiplex signal receiving apparatus for receiving received signal data indicating an orthogonal frequency division multiplex signal in which a scattered pilot signal is inserted into a predetermined subcarrier and decoding transmission data. Fourier transform means for Fourier transforming the received signal data; Characteristic specifying means for specifying a channel characteristic for a subcarrier that has transmitted a scattered pilot signal based on the received signal data Fourier-transformed by the Fourier transform means; First interpolating means for interpolating in the symbol direction data indicating the channel characteristics specified by the specifying means; and data indicating the channel characteristics interpolated in the symbol direction by the first interpolating means in the subcarrier direction. A second interpolation means for interpolating the transmission path characteristics of the data indicating the transmission path characteristics specified by the characteristic specification means. First detecting means for detecting a data level; second detecting means for detecting a data level of data indicating transmission path characteristics interpolated in the subcarrier direction by the second interpolating means; A characteristic correction unit that corrects data indicating a transmission path characteristic interpolated in the subcarrier direction by the second interpolation unit based on a detection result by the detection unit, and a transmission path characteristic corrected by the characteristic correction unit. Signal equalizing means for equalizing received signal data Fourier-transformed by the Fourier transform means using data shown, and demapping means for decoding transmission data from the received signal data equalized by the signal equalizing means. An orthogonal frequency division multiplexed signal receiving apparatus, comprising: 6. An orthogonal frequency division multiplex signal receiving method for decoding transmission data from received signal data indicating an orthogonal frequency division multiplex signal in which a scattered pilot signal is inserted into a predetermined subcarrier, comprising: A Fourier transform step of performing a Fourier transform on the basis of the received signal data subjected to the Fourier transform in the Fourier transform step, a property specifying step of specifying a transmission path characteristic for a subcarrier transmitting the distributed pilot signal, and the property specifying step. A first interpolation step of interpolating in the symbol direction the data indicating the transmission path characteristics specified in the above, and interpolating in the subcarrier direction the data indicating the transmission path characteristics interpolated in the symbol direction in the first interpolation step. A second interpolation step, and interpolation in the symbol direction in the first interpolation step. A first detection step of detecting the data level of the data, a second detection step of detecting the data level of the data interpolated in the subcarrier direction in the second interpolation step, and the first and second Based on the detection result in the detection step, a characteristic correction step of correcting data indicating a transmission path characteristic interpolated in the subcarrier direction in the second interpolation step, and using the data corrected in the characteristic correction step, A signal equalizing step of equalizing the received signal data subjected to the Fourier transform in the Fourier transform step; anda demapping step of decoding transmission data from the received signal data equalized in the signal equalization step. Characteristic orthogonal frequency division multiplex signal receiving method. 7. An orthogonal frequency division multiplexed signal receiving method for decoding transmission data from received signal data indicating an orthogonal frequency division multiplexed signal in which a scattered pilot signal is inserted into a predetermined subcarrier, comprising: A Fourier transform step of performing a Fourier transform on the basis of the received signal data subjected to the Fourier transform in the Fourier transform step, a property specifying step of specifying a transmission path characteristic for a subcarrier transmitting the distributed pilot signal, and the property specifying step. A first interpolation step of interpolating in the symbol direction the data indicating the transmission path characteristics specified in the above, and interpolating in the subcarrier direction the data indicating the transmission path characteristics interpolated in the symbol direction in the first interpolation step. A second interpolation step and a transmission path characteristic specified in the characteristic specifying step. A first detection step of detecting the data level of the data, a second detection step of detecting the data level of the data interpolated in the subcarrier direction in the second interpolation step, and the first and second Based on the detection result in the detection step, a characteristic correction step of correcting data indicating a transmission path characteristic interpolated in the subcarrier direction in the second interpolation step, and using the data corrected in the characteristic correction step, A signal equalizing step of equalizing the received signal data subjected to the Fourier transform in the Fourier transform step; anda demapping step of decoding transmission data from the received signal data equalized in the signal equalization step. Characteristic orthogonal frequency division multiplex signal receiving method.