JPH11252040A - Ofdm receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve demodulation performance by mounting the pilot carrier of received OFDM signals and judging an interfered carrier. SOLUTION: OFDM transmission signals obtained through a reception antenna 101, an RF amplifier 102, a tuner part 103 and an A/D conversion part 104 are orthognally detected in an orthogonal detection part 105, the orthogonal detection output is transformed from a time area to a frequency area by fast Fourier transformation in an FFT part 106, information transmitted from the fast Fourier transformed result is demodulated in a demodulation part 107, an error is corrected in the error correction part 108 of the demodulated result and it is outputted. At the time, the interference of the frequency selection of input signals from fast Fourier transformation output is detected from pilot signals in an interference detection part 113. Further, the interference is removed from demodulation outupt in the demodulation part 107 and the error correction part 108 based on the interference detected result and synchronization reproduction reduced in the influcene of the interference is performed in a synchronization reproduction part 112.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) transmission type receiving apparatus, and more particularly to a frequency selective interference (spurious, multipath, co-channel interference) in a received signal. The present invention relates to an improved technique when the demodulation performance is deteriorated.

[0002]

2. Description of the Related Art In recent years, digital modulation systems have been actively developed for transmission of audio signals and video signals. In particular, in digitalization of terrestrial broadcasting in Europe and Japan, the OFDM system is to be adopted as an optimal modulation system. For details of the OFDM method, refer to the document ITU-RS (TG11 / 3) or the Institute of Television Engineers of Japan Vol.17.No.54.pp7-12, BCS No.93-33 (Sep.
1993) and so on, and here, a conventional technique related to the present invention will be described.

In OFDM transmission, modulation and demodulation are performed by assigning data to a plurality of orthogonal carriers. This is because the transmitter uses IFFT for multiple symbol data.
(Inverse fast Fourier transform) processing is performed, and the reception side realizes this by performing FFT (fast Fourier transform) processing on the received data.

On the transmitting side, a scattered pilot (hereinafter, referred to as SP) signal is inserted at a rate of 1/3 in the frequency direction and a rate of 1/4 in the time direction. Synchronous detection is realized by obtaining a carrier error and performing amplitude equalization and phase equalization. That is, S
Since P is arranged at a period of four symbols, an SP signal at three carrier intervals can be obtained by observing a signal of four symbols. Therefore, the SP signal is interpolated in the frequency direction. As a result, reference signals of all carriers can be obtained, and these errors can be obtained by comparing these reference signals with the received carriers.

However, the conventional OFD as described above
In the M receiving apparatus, if spurs that match the frequency of the SP signal occur during transmission, or if a level drop due to multipath or co-channel interference occurs, the SP
The signal is affected by interference. In this case, since each SP signal is interpolated in the frequency direction, depending on the number of taps of the filter, interference of one carrier affects all symbols of several carriers, and demodulation performance is greatly deteriorated. .

Further, in synchronous reproduction, if synchronous reproduction processing is performed on a signal that has suffered co-channel interference, a large error occurs due to the influence of the interference, and accurate synchronous reproduction cannot be performed.

[0007]

As described above, in a conventional OFDM receiver using a multicarrier transmission method, a specific carrier is affected by spurious, multipath (drop in level), co-channel interference, and the like. However, since the demodulation process is performed, the demodulation performance is deteriorated, and accurate synchronous reproduction cannot be performed. Also, at the time of synchronous detection, even if one scattered pilot is disturbed (spurious or the like), interpolation processing is performed in the frequency direction to obtain the reference signals of all carriers, so that the influence of the interference is affected in the frequency direction. Will spread. In this case, if the frequency of the disturbance matches the scattered pilot,
The error rate deteriorates to a greater degree than when the information carrier is disturbed.

[0008] The present invention solves the above problems and provides an OFDM receiver capable of monitoring a pilot carrier of a received OFDM signal, determining a disturbed carrier, and improving the demodulation performance. The purpose is to do.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an OFDM receiving apparatus according to the present invention is an apparatus for receiving an OFDM transmission signal in which a pilot signal is periodically inserted into a plurality of carriers, The OFDM transmission signal is subjected to quadrature detection, this quadrature detection output is converted from the time domain to the frequency domain by fast Fourier transform, information transmitted from the fast Fourier transform result is demodulated, and errors in the demodulation result are corrected. Output, in particular, to detect, from the pilot signal, frequency selective interference of the input signal from the fast Fourier transform output, and to perform interference removal from the demodulated output based on the interference detection result. ing.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an OF according to the present invention.
1 shows a configuration of a first embodiment of a DM receiving apparatus. In this OFDM receiving apparatus, an OFDM transmission signal is transmitted through a receiving antenna 101 and an RF amplifier 102 to a tuner circuit 1.
03 is input, and channel selection is performed here. This tuning,
This is performed by adjusting the oscillation frequency of the local oscillator 111 to a desired channel frequency by a frequency control signal input to the tuning information input terminal 110.

The output of the tuner circuit 103 is A / D
The signal is converted into a digital signal by an (analog / digital) converter 104, and is converted into a baseband OFDM signal by quasi-synchronous quadrature detection of IQ in a quadrature detector 105. This baseband OFDM signal is supplied to FFT section 106.
The FFT unit 106 converts an input OFDM signal from a time domain to a frequency domain signal. A
The / D conversion clock and other clocks and timing signals used in the digital circuit are reproduced by the synchronous reproduction unit 112 from the received signal itself.

The output of the FFT unit 106 indicates the phase and amplitude of each carrier of the OFDM signal.
7 is supplied. This demodulation section 107 receives the input OF
For the DM signal, demodulation processing by synchronous detection is performed according to the modulation method. Here, the synchronous detection detects an error signal of each carrier using a scattered pilot signal inserted at a rate of 1/3 in the frequency direction and 1/4 in the time direction, and performs amplitude equalization and phase equalization. Performs equalization.

In the synchronous detection, first, the received OFDM
Since SPs are arranged in the signal at a period of 4 symbols, a reference signal at 3 carrier intervals can be obtained from the SP signals of 4 symbols. Therefore, the reference signals of all carriers are obtained by interpolating these in the frequency direction. The result of demodulation is output from an output terminal 109 after an error generated during transmission is corrected by an error correction unit 108.

On the other hand, the output of FFT section 106 is also input to interference detection section 113. The interference detection unit 113 determines the carrier affected by frequency-selective interference (spurious, multipath, or co-channel interference) by determining the state of the received pilot signal.
The result of the determination is output to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112, and is used for improving the demodulation performance.

The operation of the above configuration will be described below in comparison with a conventional device. First, the conventional O
In the FDM receiver, interference of frequency selection in received signals (spurious, multipath, or co-channel interference)
Even if a specific carrier is affected by the influence of the above, the FFT unit 106 performs the fast Fourier transform process and the demodulation unit 107 performs the demodulation process. In this case, the error correction processing is performed by the error correction unit 108, but if the correction cannot be performed due to the influence of the frequency selection system, an erroneous demodulated signal is output from the output terminal 109.

On the other hand, in the present embodiment, the FFT unit 1
06 is input to the interference detection unit 113, and the state of the pilot signal received by the interference detection unit 113 is determined, thereby receiving the influence of frequency selection-based interference (spurious, multipath, or co-channel interference). The carrier to be used is determined, and the result is output to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112 to improve the demodulation performance.

That is, the demodulation section 107 detects the error signal of each carrier using the scattered pilot signal at the time of synchronous detection and performs amplitude equalization and phase equalization. Do not use if the received frequency matches the frequency of the scattered pilot signal, and demodulate by detecting the error signal in the signal interpolated with the scattered pilot signal not affected by interference. Performance improvements can be made.
Further, the error correction unit 108 performs weighting processing such as erasure correction on carrier information affected by interference, so that the effect of interference can be improved.

FIG. 2 shows a specific configuration of the demodulation unit 107. The IQ signals subjected to the fast Fourier transform are input to input terminals 107a and 107b, respectively, and the delay unit 107c detects the amplitude error and the phase error. Delay processing of the time required for detection is performed, amplitude equalization processing is performed based on the error signal detected by the amplitude equalization section 107d, and the phase equalization section 1
Phase equalization processing is performed using the phase error signal detected at 07e, and IQ demodulated signals are output from output terminals 107f and 107g.

On the other hand, the IQ signals input to the input terminals 107a and 107b are also input to the memory 107h.
The memory unit 107h writes a scattered pilot signal for four symbols from the input IQ signal into a RAM (random access memory) and reads it out in units of one symbol. The read output is an interpolation filter 107i for countermeasures against interference. Supplied to

The interference countermeasure interpolation filter 107i receives the interference carrier information from the interference detection unit 113 through the input terminal 107n, and removes the scattered pilot signal determined to be the interference carrier based on the interference carrier information. Performs an interpolation process using only a scattered pilot signal which is not affected by interference, and outputs an interpolation filter 107j in the frequency direction.
Supplied to

The frequency interpolation filter 107j obtains reference signals for all carriers by interpolating the input scattered pilot signals at three-carrier intervals in the frequency direction, and the output is supplied to a polar coordinate converter 107k. You. The polar coordinate conversion unit 107k detects the amplitude value and the phase value of the IQ signal from the reference signals of all the carriers interpolated in the frequency direction. The amplitude detection output is supplied to the amplitude error detection unit 212, and the phase detection output is It is supplied to the phase error detection unit 107m.

The amplitude error detecting section 107l detects the amplitude error of the IQ signal by calculating the reciprocal of the input amplitude value, and the detected output is the amplitude equalizing section 107d.
And is subjected to amplitude equalization processing of the IQ signal. The phase error detection unit 107m detects the phase error signal by inverting the sign of the input phase value. The detection output is supplied to the phase equalization unit 107e, and the phase equalization processing of the IQ signal is performed. To be served.

The operation of the demodulation unit 107 having the above configuration will be described with reference to FIG. FIG. 3A shows an example of the arrangement of scattered pilot signals. Since the scattered pilots are arranged in a 4-symbol cycle, a signal at a 3-carrier interval can be obtained by observing a 4-symbol signal. Therefore, a reference signal for all carriers can be obtained by interpolating this signal in the frequency direction.

However, as shown in FIG. 3B, when spurious, multipath or co-channel interference occurs as frequency selective interference and the frequency coincides with the frequency of the scattered pilot signal, the scattered pilot signal becomes scattered. The tard pilot signal is affected by interference. In this case, as shown in FIG. 3 (c), using a scattered pilot signal that has been disturbed by frequency selection and interpolating in the frequency direction to obtain reference signals for all carriers, the number of filter taps However, the interference of one carrier affects all the symbols of several carriers, and the demodulation performance is greatly deteriorated.

On the other hand, the demodulation section 107 solves the problem by the following processing. FIG. 3 (c)
Indicates a scattered pilot signal read from the RAM of the memory unit 107h in FIG. in this case,
A scattered pilot signal for four symbols is read for four symbols in one symbol unit. Therefore, 4
The scattered pilot signals for the symbols are the same.

The read output of the memory unit 107h is:
The scattered pilot signal which has been disturbed by the frequency selection system is eliminated by the interference countermeasure interpolation filter 107i, and as shown in FIG. Is newly inserted as a scattered pilot signal. As described above, by performing the interpolation process in the frequency direction using the scattered pilot by the interpolation process, the influence of the interference is reduced, thereby improving the demodulation performance.

FIG. 4 shows a specific configuration of the interference detection unit 113. In FIG. 4, the interference detection unit 113
The output of the fast Fourier-transformed FFT unit 106 is input to the pilot signal extraction unit 113a. The pilot signal extracting section 113a extracts a pilot signal from an input signal, and its output is supplied to an integrator 113b and to a subtracting section 113c.

The integrator 113b obtains an average value by integrating the amplitude of each pilot signal, and this average value is supplied to a subtraction unit 113c. This subtraction unit 113
c is for detecting the difference between the average value of the amplitude of each pilot signal and the amplitude of each pilot signal, and the detected output is used as an error in each pilot signal unit as an absolute value calculation unit 113d.
, Where the absolute value of the error of each pilot signal is obtained.

The output of the absolute value calculation unit 113d is supplied to an integrator 113e, where the error of each pilot signal is integrated in the time direction. This processing result is output as an error signal of each pilot signal by the comparing section 113f and the averaging section 113f.
g.

Here, the error signal of each pilot signal corresponds to the C / N value of each pilot signal. The C / N value of each pilot signal is output by the averaging circuit 113g as the C / N value of all pilot signals. On the other hand, the comparator 113f
Is the C / N value of each pilot signal and the C / N value of each pilot signal.
/ N values are compared, and if the difference between the comparison results is large, it is determined that there is interference in the frequency selection system. This makes it possible to accurately determine the frequency of the interfering pilot signal. The output of the comparator 113f is output to the demodulation unit 107 and the error correction unit 108 as the above-described interference carrier information.
Is output to the synchronous playback unit 112.

Incidentally, the obtained interfering carrier information is as follows:
By enabling external output and arbitrarily monitor display, it can be used for investigating the cause of interference. The operation of the interference detection unit 113 having the above configuration will be described with reference to FIG.

In FIG. 5, spurs are present and C /
(A) when N is good, and (b) when C / N is bad. Also, (c) shows when the multipath exists and the C / N is good, and (d) shows when the C / N is bad. Here, in the interference detection unit 113, C / N error = | each pilot carrier−average value of each pilot carrier |, interference error = |
Error of each pilot carrier-average value of error of all pilot carriers |

As can be seen from FIGS. 5A to 5D, when the error between the pilot carriers and the average value of the pilot carriers is large, the C / N is in a bad state, and when the error is small, the C / N is good. In state. Therefore, when the detected error of each pilot carrier has a large difference from the average value of the errors of all the pilot carriers, the interference detection unit 113 determines that interference of the frequency selection system has been received. .

The comparison result obtained by the comparison unit 113f is supplied to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112. As a result, an error signal is detected in the signal interpolated by the scattered pilot signal not affected by the interference in the demodulation unit 107, and the error correction unit 108 performs error correction on the lost signal, and performs synchronization. Synchronous reproduction with a small error is performed from a signal that is not disturbed by the reproduction unit 112, deterioration of demodulation performance due to interference by frequency selection is improved, and a signal without error can be output.

By the way, in the case of terrestrial television broadcasting, in transition to digital broadcasting, it is necessary to mix digital broadcasting signals and analog broadcasting signals of the current system on the same channel for a certain period. Therefore, there is a high possibility that the analog broadcast wave will cause the same channel interference due to the digital broadcast wave.

FIG. 6 shows the case where the analog signal band overlaps the channel band of the OFDM broadcast signal as described above.
It shows an example of co-channel interference received by an FDM signal, where (a) shows the spectrum of an analog television broadcast signal and (b) shows the transmission band of an OFDM signal.

The analog television broadcast signal is shown in FIG.
As shown in (a), the video carrier, the color subcarrier, and the audio carrier have high peaks. When signals having such peak components coexist in the same channel, the OFDM signal becomes
As shown in (b), the band B around each peak component is affected and interferes with frequency selection.

FIG. 7 shows a specific configuration of the interference detection unit 113 having a function to solve the above problem.
However, in FIG. 7, the same parts as those in FIG. 4 are denoted by the same reference numerals, and different parts will be described here.

First, the C / N value of each carrier obtained by the integrator 113e shown in FIG. 7 is supplied to the averaging unit 113g, and all C / Ns are obtained, and at the same time, the carrier extracting unit within the analog broadcast peak band. 113h and the carrier extracting unit 113j in the analog broadcast peak band.
Analog Broadcast Peak Band Carrier Extraction Unit 113h
Extracts a pilot signal in a band B portion expected to be subjected to co-channel interference by an analog broadcast signal in FIG. 6B. In addition, in FIG. 6B, the analog broadcast peak out-of-band carrier extracting unit 113j extracts a pilot signal in a portion of the band A which is expected not to be disturbed by the analog broadcast signal. These extracted outputs are output to averaging units 113i and 113i, respectively.
After averaging with k, the comparison unit 113f compares them. Here, for example, when the difference between the two is equal to or greater than a specified value, it is determined that there is co-channel interference, and when it is less than the specified value, it is determined that there is no co-channel interference. This determination result is supplied to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112 as interference carrier information.

That is, the interference detection unit 11 having the above configuration
In 3, the pilot signal within the carrier band of video, color and audio is extracted by the carrier extracting section 113h in the analog broadcasting peak band, the averaged result is outputted by the averaging section 113i to the comparing section 113f, and the carrier extracting section outside the analog broadcasting peak band is extracted. A pilot signal outside the carrier band of video, color, and audio is extracted by the unit 113j, and the averaged result is output to the comparison unit 113f by the averaging unit 113k. The comparison unit 113f compares the pilot signal within the analog broadcast peak band and the pilot signal outside the band. Is performed. Thereby, the comparison unit 1
At 13f, the pilot signal of the frequency in the video band (around the luminance carrier, the audio carrier, and the chrominance carrier) that is likely to cause the same channel interference from the analog broadcasting is compared with the pilot signal of the frequency outside the video band, and whether there is the same channel interference. Is determined.

The comparison result obtained by the comparison unit 113f is supplied to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112. As a result, the demodulation section 107 detects an error signal in the signal interpolated by the scattered pilot signal not affected by the co-channel interference, and the error correction section 108 performs error correction on the lost signal. As a result, it is possible to improve the deterioration of the demodulation performance due to the interference of the frequency selection system, and to output an error-free signal.

FIG. 8 is a diagram showing a specific configuration of the synchronous reproduction unit 112. Quadrature detection unit output 105 after quadrature detection
Is input to the synchronous playback unit 112. The input signal is
OFD by co-channel interference removal filter unit 112a
The peak frequency of analog co-channel interference is removed from the M signal, and input to the switching unit 112b. The switching unit 112b selects the output of the quadrature detection unit 105 when there is no co-channel interference due to the interference carrier information (co-channel interference) signal of the interference detection unit 113,
When there is co-channel interference, the co-channel interference removal filter section output 112a is selected and output to the clock / timing reproduction section 112c. As a result, the clock / timing reproducing unit 112c can perform accurate synchronous reproduction from a signal containing all OFDM carrier components when there is no co-channel interference, and removes a frequency with a large co-channel interference when there is co-channel interference. By performing synchronous reproduction using a frequency signal, it is possible to reduce the influence of interference.

FIG. 9 is a diagram for explaining the operation of the filter for removing co-channel interference (in the case of band elimination characteristics) shown in FIG. The OFDM signal shown in FIG. 9A and the analog broadcast shown in FIG.
The input signal of the M receiver is OFD as shown in FIG.
It becomes M signal + analog broadcast signal spectrum. FIG.
(D) shows the band elimination characteristics of the same-channel interference elimination filter 12a.

That is, by removing the unnecessary video carrier, chrominance subcarrier and audio carrier by the filter characteristics shown in FIG. 9D, a signal having a frequency less affected by the same channel interference is extracted. .

Therefore, when co-channel interference is detected, synchronous reproduction is passed through a filter shown in FIG. 9 (d). Synchronous playback that is not affected can be performed.

FIG. 10 shows a configuration of an embodiment in which the present invention is applied to an OFDM receiving apparatus of the diversity receiving system. In this apparatus, a plurality of (two in the figure) receiving antennas 114a having different directivities are provided.
At 114b, the OFDM transmission signal is received, and an RF amplifier, a tuner circuit, a local oscillator for tuning, a quadrature detector,
Channel selection, quadrature detection, and FFT processing are performed by the demodulation system (A) 115a and the demodulation system (B) 115b, which are composed of FFT units, and input to the switching unit 116.

On the other hand, the outputs of the demodulation system (A) 115a and the demodulation system (B) 115b are output from the interference detection unit (A), respectively.
The reception state (amplitude and phase) of the interference is monitored by the interference detection unit 117a and the interference detection unit (B) 117b, respectively, and the comparison unit 118 is monitored.
And compare the strength of the disturbance. From the comparison result, the switching system 116 selects the system with the least disturbance,
After demodulation by the detection unit 119, error correction is performed by the error correction unit 120, and a demodulated signal is extracted from the output terminal 121.

According to the above configuration, demodulation processing is performed on the OFDM transmission signal from the direction with the least interference.
A good demodulated signal can be obtained without performing interference removal processing. This device is particularly effective when used for a simple type for use in a vehicle. When performing interference removal processing,
The above-described method, that is, the detection unit 119 and the error correction unit 120 perform pilot signal interpolation processing and erasure correction processing based on the interference carrier information obtained by the interference detection unit of the selected system.

[0049]

As described above, according to the present invention, there is provided an OFDM receiving apparatus capable of monitoring a pilot carrier of a received OFDM signal, determining a disturbed carrier, and improving demodulation performance. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a configuration of an OFDM receiver according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a specific configuration of a demodulation unit of the embodiment.

FIG. 3 is a diagram illustrating an equalization calculation process of a demodulation unit in FIG. 2;

FIG. 4 is an exemplary block circuit diagram showing a specific configuration of a disturbance detection unit according to the embodiment;

FIG. 5 is a view for explaining interference detection in FIG. 4;

FIG. 6 is an exemplary view for explaining co-channel interference detection according to the embodiment;

FIG. 7 is a block circuit diagram showing a specific configuration in the case where co-channel interference is detected in the interference detection unit of the embodiment.

FIG. 8 is a block circuit diagram showing a specific configuration of a synchronous reproduction unit of the embodiment.

FIG. 9 is a view for explaining the operation of the co-channel interference removal filter of FIG. 8;

FIG. 10 is a block circuit diagram showing a configuration of an OFDM receiver using a diversity reception system according to another embodiment of the present invention.

[Explanation of symbols]

101 ... receiving antenna, 102 ... RF amplifier, 103 ...
Tuner circuit, 104: A / D converter, 105: Quadrature detection unit, 106: FFT unit, 107: Demodulation unit, 108: Error correction unit, 109: Output terminal, 110: Tuning information input terminal, 111: Local oscillator , 112... Synchronous playback unit, 113
... Disturbance detector 107a, 107b.
c: delay section, 107d: amplitude equalization section, 107e: phase equalization section, 107f, 107g: output terminal, 107h: memory section, 107i: interpolation filter for interference measures, 107j ...
Frequency direction interpolation filter, 107k ... polar coordinate converter, 1
07l: Amplitude error detector, 107m: Phase error detector,
107n: input terminal, 112a: filter unit for removing same-channel interference, 112b: switching unit, 112c: clock / timing reproducing unit, 113a: pilot signal extracting unit, 113b: integrator, 113c: subtracting unit, 113
d ... absolute value calculation unit, 113e ... integrator, 113f ... comparison unit, 113g ... average unit, 113h ... carrier extraction unit in video band, 113i ... average unit, 113j ... carrier extraction unit outside video band, 113k ... average unit 114a, 1
14b: reception antenna, 115a, 115b: demodulation system, 116: switching unit, 117a, 117b: interference detection unit, 118: comparison unit, 119: detection unit, 120: error correction unit, 121: output terminal.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 7/081 H04N 7/08 Z // H04N 5/44 (72) Inventor Takashi Seki 8 Shinsugita-cho Isogo-ku, Yokohama-shi, Kanagawa In the Toshiba Multimedia Technology Research Laboratories (72) Inventor Yuji Ohashi 3-3-9, Shimbashi, Minato-ku, Tokyo Toshiba AV EE Corporation

Claims (8)

[Claims] 1. An OFDM receiving apparatus for receiving an orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) transmission signal in which a pilot signal is periodically inserted into a plurality of carriers, comprising: an orthogonal detection means for orthogonally detecting the OFDM transmission signal; Fast Fourier transform means for transforming the quadrature detection output obtained by this means from the time domain to the frequency domain by fast Fourier transform; demodulating means for demodulating information transmitted from the fast Fourier transform result of this means; An OFDM receiver comprising: an error correction unit for correcting an error in the obtained demodulation result; and an interference detection unit for detecting, from the fast Fourier transform output, a frequency selective interference of an input signal from the pilot signal. apparatus. 2. The OF according to claim 1, further comprising interference removal means for removing interference from an output of said demodulation means based on a result of interference detection by said interference detection means.
DM receiver. 3. The OFDM according to claim 2, wherein said interference removing means comprises means for erasing data of a carrier having a frequency selective interference based on a detection result of said interference detecting means. Receiver. 4. An OFDM transmission signal in which one
When a scattered pilot signal is inserted at a rate of ３, 1/4 in the time direction, the interference canceling means:
A memory means for writing and reading a scattered pilot signal for four symbols from an output of the fast Fourier transform means; and a scattered frequency of an output of the memory means having a frequency detected as having interference by the interference detection result. 3. The signal processing apparatus according to claim 2, further comprising an interpolation filter means for countermeasures against interference, which interpolates the tailed pilot signal from the scattered pilot signals before and after the interference.
FDM receiver. 5. An error detecting means for detecting a difference between an amplitude of each pilot signal of a signal output from the fast Fourier transform means and a value obtained by averaging the amplitude of each pilot signal for each pilot signal. Integrating means for averaging the error signal obtained by this means in each pilot signal unit, and averaging means for obtaining the average value of all pilot signals from the average value of errors in each pilot signal unit obtained by this means. 2. The OFDM receiving apparatus according to claim 1, further comprising detecting a C / N of the received OFDM signal based on an average result of all the pilot signals. 6. An error detecting means for detecting a difference between an amplitude of each pilot signal of a signal output from the fast Fourier transform means and a value obtained by averaging the amplitude of each pilot signal for each pilot signal. Integrating means for averaging the error signal obtained by this means for each pilot signal unit, averaging means for obtaining the average value of all pilot signals from the average value of the error of each pilot signal unit obtained by this means, Comparing means for comparing the result obtained by this means with the result obtained by integrating the error signal for each pilot signal, and detecting the frequency selective interference of the received OFDM signal based on the compared result. The OFDM receiving apparatus according to claim 1, wherein: 7. When an analog television broadcast signal is transmitted in the same band as said OFDM transmission signal, said interference detection means comprises an interference detector for a luminance carrier, a voice carrier and a chrominance carrier of said analog television broadcast signal. Means for detecting co-channel interference by comparing the state of pilot signals in a band that is susceptible to interference and a band that is less susceptible to interference. Co-channel interference removal is performed according to the detection result of the co-channel interference. The OFDM receiver according to claim 1, wherein 8. An OFDM receiving apparatus for diversity receiving orthogonal frequency division multiplexing (OFDM) transmission signals, wherein said OFDM signals are received by different antennas.
A plurality of quadrature detection / domain conversion means for performing quadrature detection on an FDM transmission signal and performing conversion from a time domain to a frequency domain by fast Fourier transform; and a plurality of quadrature detection / domain conversion means for detecting interference in the respective systems. And a comparison means for comparing the results of detection of interference in each system to determine a system with less interference, and a demodulation output of a system with less interference from all systems input based on the results of the comparison means. An OFDM receiving apparatus comprising: a switching unit for selecting a signal; a demodulation unit for demodulating a selection output signal of the switching unit; and an error correction unit for correcting an error in a demodulation result obtained by the switching unit.