JP3363086B2 - OFDM receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) transmission system receiver, and in particular, there is frequency selective interference (spurious, multipath, co-channel interference) in a received signal and its influence. The present invention relates to an improved technique when the demodulation performance deteriorates.

[0002]

2. Description of the Related Art In recent years, digital modulation methods have been actively developed in the transmission of audio signals and video signals. Especially, in the digitization of terrestrial broadcasting in Europe and Japan, the OFDM system is supposed to be adopted as the optimum modulation system. For details of the OFDM system, refer to the ITU-RS contribution (TG11 / 3) or Research Report of the Television Society of Japan Vol.17.No.54.pp7-12, BCS 93-33 (Sep.
1993) and the like, and here, a conventional technique related to the present invention will be described.

In OFDM transmission, data is assigned to a plurality of carriers that are orthogonal to each other to perform modulation and demodulation. This is because the transmitter side uses IFFT for multiple symbol data.
This is realized by performing (inverse fast Fourier transform) processing and performing FFT (fast Fourier transform) processing on the reception data on the receiving side.

Further, a scattered pilot (hereinafter, SP) signal is inserted at a rate of 1/3 in the frequency direction and 1/4 in the time direction on the transmission side, and the SP signal is detected on the reception side to detect each SP signal. Synchronous detection is realized by obtaining the carrier error and performing amplitude equalization and phase equalization. That is, S
Since Ps are arrayed in a 4-symbol period, SP signals with 3-carrier intervals can be obtained by observing 4-symbol signals. Therefore, this SP signal is interpolated in the frequency direction. By this means, reference signals of all carriers can be obtained, and respective errors can be obtained by comparing these reference signals with received carriers.

However, the conventional OFD as described above is used.
In the M receiver, if a spurious signal that coincides with the frequency of the SP signal is generated during transmission, a level drop due to multipath, co-channel interference, etc.
The signal is disturbed. In this case, since each SP signal is interpolated in the frequency direction, interference of one carrier affects all symbols of several carriers, depending on the number of taps of the filter, and demodulation performance is greatly deteriorated. .

Further, in the synchronous reproduction, if the synchronous reproduction processing is carried out with a signal which has received the same channel interference, a large error occurs due to the influence of the interference, and the accurate synchronous reproduction cannot be performed.

[0007]

As described above, in the conventional OFDM receiver using the multi-carrier transmission method, when a specific carrier is affected by spurious, multi-path (level drop), co-channel interference, etc. However, since demodulation processing is performed, demodulation performance deteriorates, and accurate synchronous reproduction cannot be performed. In addition, even if one scattered pilot receives interference (spurious waves) during synchronous detection, interpolation processing is performed in the frequency direction to obtain the reference signals for all carriers, so the effect of interference is It will spread. In this case, if the frequency of the interference matches the scattered pilot,
The error rate deteriorates more than when the information carrier is disturbed.

The present invention solves the above problems and provides an OFDM receiving apparatus capable of monitoring a pilot carrier of a received OFDM signal, determining a carrier which is disturbing, and improving demodulation performance. The purpose is to do.

[0009]

In order to achieve the above object, an OFDM receiving apparatus according to the present invention comprises a plurality of carriers.
A device for receiving an OFDM transmission signal in which a pilot signal is periodically inserted into the OFDM transmission signal, wherein the OFDM transmission signal is quadrature-detected, and the quadrature detection output is transformed from the time domain to the frequency domain by Fast Fourier Transform for each carrier. A pilot signal and symbol data are obtained, demodulated data is obtained by equalizing amplitude and phase based on the pilot signal for symbol data of each carrier, and error-corrected and outputted. When a carrier with frequency-selective interference is detected from the pilot signal obtained by the fast Fourier transform, the data of the interfered carrier is erased and subjected to error correction.
The interference is removed from the demodulation output. When a carrier with frequency selective interference is detected in the interference detection, the pilot signal of the interfered carrier is interpolated with another pilot signal that is not interfered, and the interpolated pilot is used. Interference is removed from the demodulated output by equalizing the amplitude and phase of the symbol data based on the signal.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described 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 which an OFDM transmission signal passes through a receiving antenna 101 and an RF amplifier 102, and a tuner circuit 1
It is input to 03, and tuning is performed here. This channel is
This is performed by adjusting the oscillation frequency of the local oscillator 111 to a desired channel frequency with a frequency control signal input to the tuning information input terminal 110.

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

The output of the FFT section 106 indicates the phase and amplitude of each carrier of the OFDM signal, and the demodulation section 10
7 is supplied. This demodulation unit 107 receives the OF
The DM signal is demodulated by synchronous detection according to the modulation method. Here, the synchronous detection detects the error signal of each carrier by using a scattered pilot signal inserted at a rate of ⅓ in the frequency direction and ¼ in the time direction, and performs amplitude equalization and phase Equalization is performed.

In synchronous detection, first, the received OFDM
Since SPs are arranged in a signal in a 4-symbol cycle, a 4-symbol SP signal provides a reference signal at 3-carrier intervals. Therefore, the reference signals of all carriers are obtained by interpolating these in the frequency direction. The demodulated result is output from the output terminal 109 after the error occurring during transmission is corrected by the error correction unit 108.

On the other hand, the output of the FFT section 106 is also input to the interference detection section 113. The interference detecting unit 113, by determining the status of the received pilot signals, intended to determine the carrier that are affected by frequency selective interference (spurious or multipath and co-channel interference),
The determination result 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 structure will be described below in comparison with a conventional device. First, conventional O
In FDM receiver, interference frequency selectivity in the received signal (spurious and multipath and co-channel interference)
Even if a specific carrier is affected by the influence of, the FFT unit 106 performs the fast Fourier transform process and the demodulation unit 107 performs the demodulation process. In this case, the processing of the error correction is performed in the error correction section 108, if it can not correct the influence of interference of frequency selective <br/> are demodulated signal with error from being outputted from an output terminal 109.

On the other hand, in this embodiment, the FFT unit 1
The output of 06 is input to the interference detecting unit 113, by determining the state of the pilot signal received by the interference detecting unit 113, under the influence of interference of frequency selective (spurious and multipath and co-channel interference) By determining which carrier is present and outputting the result to the demodulation unit 107, the error correction unit 108, and the synchronous reproduction unit 112, the demodulation performance is improved.

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

FIG. 2 shows a concrete structure of the demodulation section 107. IQ signals which have been subjected to fast Fourier transform are inputted to input terminals 107a and 107b respectively, and an amplitude error and a phase error are delayed by a delay section 107c. The delay processing of the time required for detection is performed, the amplitude equalization processing is performed by the error signal detected by the amplitude equalization unit 107d, and the phase equalization unit 1
Phase equalization processing is performed by 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 signal input to the input terminals 107a and 107b is also input to the memory section 107h.
This memory unit 107h writes a scattered pilot signal for 4 symbols from the input IQ signal in a RAM (random access memory) and reads it in 1-symbol units, and the read output is an interference filter interpolation filter 107i. Is 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 by the interference carrier information. , The interpolation processing is performed using only the scattered pilot signals that are not affected by the interference, and the output is the interpolation filter 107j in the frequency direction.
Is supplied to.

The frequency interpolation filter 107j finds the reference signals of all carriers by interpolating the input scattered carrier pilot signals at intervals of three carriers in the frequency direction, and the output thereof is supplied to the polar coordinate conversion unit 107k. It The polar coordinate conversion unit 107k detects the amplitude value and the phase value of the IQ signal from the reference signals of all 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 detector 107l detects the amplitude error of the IQ signal by obtaining the reciprocal of the input amplitude value, and the detection output is the amplitude equalizer 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, and the detection output is supplied to the phase equalization unit 107e to perform the phase equalization processing of the IQ signal. Be used for.

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

[0024] However, as shown in FIG. 3 (b), if the spurious and multipath and co-channel interference occurs, its frequency coincides with the frequency of the scattered pilot signal as a frequency-selective interference, Sukya' The Tard Pilot signal is subject to interference. In this case, as shown in FIG. 3 (c), by using the scattered pilot signal to the affected frequency selectivity and by interpolation in the frequency direction finding the reference signals of all carriers, the number of taps of the filter However, the interference of one carrier affects all symbols of several carriers, and demodulation performance is significantly deteriorated.

On the other hand, the demodulation section 107 solves the problem by the following processing. Figure 3 (c)
Indicates a scattered pilot signal read from the RAM of the memory unit 107h in FIG. in this case,
The scattered pilot signals for 4 symbols are read out for 4 symbols in units of 1 symbol. Therefore, 4
The scattered pilot signals for the symbols are the same.

The read output of the memory section 107h is
Scattered pilot signal to the affected frequency selectivity is eliminated by anti-jamming interpolation filter 107i, as shown in FIG. 3 (d), before and after the scattered pilot signal from, for example, linear interpolation without influence of disturbance The signal obtained by is newly inserted as a scattered pilot signal. In this way, by performing the interpolation processing in the frequency direction using the scattered pilot by the interpolation processing, the influence of interference is reduced, and thereby the demodulation performance can be improved.

FIG. 4 shows a specific structure of the interference detecting section 113. In FIG. 4, the interference detection unit 113
The output of the FFT unit 106 subjected to the fast Fourier transform is input to the pilot signal extraction unit 113a of. The pilot signal extraction unit 113a extracts a pilot signal from the input signal, and its output is supplied to the integrator 113b and the subtraction unit 113c.

The integrator 113b obtains an average value by integrating the amplitude of each pilot signal, and this average value is supplied to the subtracting section 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 detection output is an absolute value calculation unit 113d as an error in units of each pilot signal.
Where the absolute value of the error of each pilot signal is determined.

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

The error signal of each pilot signal corresponds to the C / N value of each pilot signal. The averaging circuit 113g outputs the C / N value of each pilot signal 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 of all pilot signals
/ N compares the value, if the difference between the result of comparison is large, it is determined that there is a disturbance of the frequency selectivity. Thereby, the frequency of the interfering pilot signal can be accurately determined. The output of the comparator 113f is the demodulation unit 107 and the error correction unit 108 as the above-mentioned interference carrier information.
Is output to the synchronous reproduction unit 112.

The interference carrier information obtained here is
By enabling external output and arbitrary 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, spurious is present and C /
(A) shows when N is good, and (b) shows when C / N is bad. Further, when multipath exists and C / N is good, (c) is shown, and when C / N is bad, (d) is shown. Here, in the interference detection unit 113, C / N error = | each pilot carrier−average value of each pilot carrier |, interference error = |
It is calculated as the error of each pilot carrier minus the average value of the errors of all pilot carriers.

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

The determination result of the comparing section 113f thus obtained is supplied to the demodulating section 107, the error correcting section 108 and the synchronous reproducing section 112. As a result, the demodulation unit 107 detects an error signal in the signal interpolated by the scattered pilot signal that is not affected by the interference, and the error correction unit 108 performs error correction on the lost signal, and the synchronization is performed. The reproduction unit 112 can perform the synchronous reproduction with a small error from the signal without interference, improve the deterioration of the demodulation performance due to the interference of the frequency selectivity , and output the error-free signal.

By the way, in the terrestrial television broadcasting, it is indispensable to mix the digital broadcasting signal and the analog broadcasting signal of the current system on the same channel for a certain period when shifting to the digital broadcasting. Therefore, analog broadcast waves are likely to cause co-channel interference due to digital broadcast waves.

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

The analog television broadcast signal is shown in FIG.
As shown in (a), the image carrier, the color subcarrier, and the audio carrier have high peaks. When signals having such peak components are mixed in the same channel, the OFDM signal is
Band B around each peak components as shown in (b) is affected, disturbed frequency selectivity.

FIG. 7 shows a specific configuration of the interference detection unit 113 having a function of solving 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 to obtain all C / N, and at the same time, the carrier extracting unit in the analog broadcast peak band. 113h and the analog broadcast peak band carrier extraction unit 113j are supplied.
Analog broadcast peak band carrier extraction unit 113h
In FIG. 6 (b), the pilot signal of the part of the band B which is expected to be subjected to co-channel interference by the analog broadcast signal is extracted. Also, the analog broadcast peak out-of-band carrier extraction unit 113j extracts the pilot signal in the part of the band A that is not expected to be disturbed by the analog broadcast signal in FIG. 6B. These extracted outputs are the average parts 113i and 113, respectively.
After being averaged by 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 co-channel interference is present, and when the difference is less than the specified value, it is determined that co-channel interference is not present. This determination result is supplied to the demodulation unit 107, the error correction unit 108, and the synchronization reproduction unit 112 as the interference carrier information.

That is, the interference detection section 11 having the above configuration
In 3, the analog broadcast peak band carrier extraction unit 113h extracts the pilot signals in the video, color and audio carrier bands, and the averaging unit 113i outputs the averaged result to the comparison unit 113f to extract the analog broadcast peak band outside carrier. The part 113j extracts the pilot signal outside the carrier band of the video, color and audio, and the averaging part 113k outputs the averaged result to the comparison part 113f, and the comparison part 113f compares the pilot signal within the analog broadcast peak band and outside the band. Is to do. As a result, the comparison unit 1
At 13f, the pilot signals of the frequency within the video band (around the luminance carrier, the audio carrier, and the chrominance carrier) and the frequency outside the video band are compared to determine whether there is co-channel interference from analog broadcasting. Is determined.

The determination result of the comparing section 113f thus obtained is supplied to the demodulating section 107, the error correcting section 108 and the synchronous reproducing section 112. As a result, the demodulation unit 107 detects an error signal in the signal interpolated by the scattered pilot signal that is not affected by co-channel interference, and the error correction unit 108 performs error correction on the lost signal. as becomes, it is possible to improve the deterioration of the demodulation performance caused by interference of the frequency selectivity, it is possible to output a signal without error.

FIG. 8 is a diagram showing a specific configuration of the synchronous reproduction section 112. Output 105 of quadrature detection section that has been quadrature detected
Is input to the synchronous reproduction unit 112. The input signal is
The OFD is performed by the co-channel interference removal filter unit 112a.
The analog co-channel interference peak frequency is removed from the M signal, and the signal is 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 unit output 112a is selected and output to the clock / timing reproducing unit 112c. As a result, the clock / timing recovery unit 112c can perform accurate synchronous reproduction from a signal including all OFDM carrier components when there is no co-channel interference, and removes frequencies with large co-channel interference when co-channel interference is present. It is possible to reduce the influence of interference by performing the synchronous reproduction with the frequency signal.

FIG. 9 is a diagram for explaining the operation of the co-channel interference elimination filter (when the band elimination characteristic is used) of FIG. Since the OFDM signal shown in (a) of FIG. 9 and the analog broadcast shown in (b) of FIG.
The input signal of the M receiver is OFD as shown in FIG.
M signal + analog broadcast signal spectrum. Figure 9
(D) shows the band elimination characteristic of the co-channel interference elimination filter 12a.

That is, by removing the unnecessary video carrier, color subcarrier and audio carrier by the filter characteristic shown in FIG. 9D, a signal of a frequency less affected by co-channel interference in FIG. 9E is extracted. .

Therefore, when co-channel interference is detected, synchronous reproduction is passed through the filter shown in FIG. 9 (d) to prevent interference of analog broadcasting by the OFDM signal that does not contain signal components of analog type. Synchronous playback can be performed without being affected.

FIG. 10 shows a configuration of an embodiment when the present invention is applied to an OFDM receiving apparatus of a diversity receiving system. In this device, a plurality of systems (two systems in the figure) of receiving antennas 114a having different directivities,
Each of 114b receives an OFDM transmission signal, an RF amplifier, a tuner circuit, a local oscillator for tuning, a quadrature detection unit,
The demodulation system (A) 115a and the demodulation system (B) 115b, which are FFT units, perform channel selection, quadrature detection, and FFT processing, and input the result to the switching unit 116.

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

According to the above configuration, since the 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 the interference removal processing. This device is particularly effective when it is used for a simple vehicle-mounted type. When performing interference removal processing,
This can be realized by the above-described method, that is, the detection unit 119 and the error correction unit 120 perform the pilot signal interpolation processing and the 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 receiver capable of improving the demodulation performance by monitoring the pilot carrier of the received OFDM signal, determining the carrier which is disturbing. Can be provided.

[Brief description of 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 same embodiment.

FIG. 3 is a diagram illustrating equalization calculation processing of a demodulation unit in FIG.

FIG. 4 is a block circuit diagram showing a specific configuration of an interference detection unit of the same embodiment.

FIG. 5 is a diagram illustrating the interference detection of FIG.

FIG. 6 is a diagram for explaining co-channel interference detection of the same embodiment.

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

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

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

FIG. 10 is a block circuit diagram showing a configuration of an OFDM receiving apparatus according to a diversity receiving system as another embodiment of the present invention.

[Explanation of Codes] 101 ... Receiving Antenna, 102 ... RF Amplifier, 103 ...
Tuner circuit, 104 ... A / D converter, 105 ... Quadrature detection section, 106 ... FFT section, 107 ... Demodulation section, 108 ... Error correction section, 109 ... Output terminal, 110 ... Channel selection information input terminal, 111 ... Local oscillator , 112 ... Synchronous reproduction unit, 113
... Interference detection section, 107a, 107b ... Input terminal, 107
c ... delay part, 107d ... amplitude equalization part, 107e ... phase equalization part, 107f, 107g ... output terminal, 107h ... memory part, 107i ... interference countermeasure interpolation filter, 107j ...
Frequency direction interpolation filter, 107k ... Polar coordinate conversion unit, 1
07l ... Amplitude error detector, 107m ... Phase error detector,
107n ... Input terminal, 112a ... Co-channel interference removal filter section, 112b ... Switching section, 112c ... Clock / timing recovery section, 113a ... Pilot signal extraction section, 113b ... Integrator, 113c ... Subtraction section, 113
d ... Absolute value calculation unit, 113e ... Integrator, 113f ... Comparison unit, 113g ... Averaging unit, 113h ... In-video band carrier extraction unit, 113i ... Averaging unit, 113j ... Out-of-video band carrier extraction unit, 113k ... Averaging unit, 114a, 1
14b ... Receiving antennas, 115a, 115b ... Demodulation system, 116 ... Switching section, 117a, 117b ... Interference detection section, 118 ... Comparison section, 119 ... Detection section, 120 ... Error correction section, 121 ... Output terminal.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Seki, Takashi Seki 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa, Toshiba Multimedia Technology Laboratory (72) Inventor, Yuji Ohashi 3-chome, Shinbashi, Tokyo No. within Toshiba A.V.E. Co., Ltd. (56) Reference JP-A-5-75568 (JP, A) JP-A-9-284191 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) H04J 11/00

Claims (11)

(57) [Claims] 1. A pilot signal periodically on a plurality of carriers.
In an OFDM receiving apparatus for receiving an orthogonal frequency division multiplexing (hereinafter referred to as OFDM) transmission signal in which is inserted, an orthogonal detection means for performing orthogonal detection of the OFDM transmission signal, and an orthogonal detection output obtained by this means by a fast Fourier transform. A fast Fourier transform means for converting from the time domain to the frequency domain to obtain a pilot signal and symbol data for each carrier, and the symbol data of each carrier obtained by this means are equalized in amplitude and phase based on the pilot signal and demodulated. Demodulation means for obtaining data, interference detection means for detecting a carrier that has received frequency selective interference from the pilot signal obtained by the fast Fourier transform means, and error correction is applied to the demodulated data obtained by the demodulation means. An error correction means, wherein the error correction means is a frequency detector in the interference detection means. When the carrier has received the interference 択性 is detected, the lost processes the data carrier to the affected OFDM receiving apparatus comprising: a erasure correction means for performing error correction. 2. A pilot signal periodically on a plurality of carriers.
In an OFDM receiving apparatus for receiving an orthogonal frequency division multiplexing (hereinafter referred to as OFDM) transmission signal in which is inserted, an orthogonal detection means for performing orthogonal detection of the OFDM transmission signal, and an orthogonal detection output obtained by this means by a fast Fourier transform. A fast Fourier transform means for converting from the time domain to the frequency domain to obtain a pilot signal and symbol data for each carrier, and the symbol data of each carrier obtained by this means are equalized in amplitude and phase based on the pilot signal and demodulated. Demodulation means for obtaining data, interference detection means for detecting a carrier that has received frequency selective interference from the pilot signal obtained by the fast Fourier transform means, and error correction is applied to the demodulated data obtained by the demodulation means. Error demodulation means, and the demodulation means selects the frequency by the interference detection means. When an interfering carrier of is detected, interpolating means for interpolating the pilot signal of the interfering carrier with another uninterrupted pilot signal is provided, and based on the pilot signal interpolated by this means An OFDM receiver characterized by equalizing the amplitude and phase of symbol data. 3. A pilot signal periodically on a plurality of carriers.
In an OFDM receiving apparatus for diversity receiving an Orthogonal Frequency Division Multiplexing (hereinafter, referred to as OFDM) transmission signal in which the O is inserted, the O
A plurality of quadrature detection means for performing quadrature detection of the FDM transmission signal, and a quadrature detection output provided by the corresponding quadrature detection means from the time domain to the frequency domain by fast Fourier transform. A plurality of fast Fourier transform means for obtaining a pilot signal and symbol data for each carrier by conversion, and provided corresponding to the plurality of fast Fourier transform means,
All of the plurality of quadrature detection / region conversion means by the plurality of interference detection means for detecting a carrier receiving frequency selective interference from the pilot signal obtained by the corresponding fast Fourier transform means Comparing means for comparing the results of detecting interference in the system of 1 to determine the system with less interference, and the output of the system with the least interference from all the systems of the plurality of quadrature detection / region conversion means based on the result of this comparing means. Of the output of the quadrature detection / region conversion means of the system selected by this switching means, and demodulated data is obtained by equalizing the amplitude and phase of the symbol data of each carrier based on the pilot signal. Demodulating means for obtaining the demodulated data, and error correcting means for performing error correction on the demodulated data obtained by this means. If the carrier to the affected frequency selective detected by the interference detecting means, disappeared process the data carrier to the affected OFDM receiving apparatus comprising: a erasure correction means for performing error correction. 4. A pilot signal periodically on a plurality of carriers.
In an OFDM receiving apparatus for diversity receiving an Orthogonal Frequency Division Multiplexing (hereinafter, referred to as OFDM) transmission signal in which the O is inserted, the O
A plurality of quadrature detection means for performing quadrature detection of the FDM transmission signal, and a quadrature detection output provided by the corresponding quadrature detection means from the time domain to the frequency domain by fast Fourier transform. A plurality of fast Fourier transform means for obtaining a pilot signal and symbol data for each carrier by conversion, and provided corresponding to the plurality of fast Fourier transform means,
All of the plurality of quadrature detection / region conversion means by the plurality of interference detection means for detecting a carrier receiving frequency selective interference from the pilot signal obtained by the corresponding fast Fourier transform means Comparing means for comparing the results of detecting interference in the system of 1 to determine the system with less interference, and the output of the system with the least interference from all the systems of the plurality of quadrature detection / region conversion means based on the result of this comparing means. Of the output of the quadrature detection / region conversion means of the system selected by this switching means, and demodulated data is obtained by equalizing the amplitude and phase of the symbol data of each carrier based on the pilot signal. Demodulating means for obtaining the demodulated data, and error correcting means for performing error correction on the demodulated data obtained by the means. Interpolation for interpolating the pilot signal of the disturbed carrier with other undisturbed pilot signal when the carrier with frequency selective interference is detected by the interference detection means of the system selected by the replacement means An OFDM receiving apparatus comprising: means for equalizing the amplitude and phase of symbol data based on a pilot signal interpolated by the means. 5. The interpolating means is provided in the OFDM transmission signal.
, The carrier number is k and the symbol number is n,
k = 3 (n mod 4) + 12p (mod is remainder calculation
, And p is an integer)
When the lot signal is inserted, the fast Fourier transform
Unit of pilot signal for 4 symbols from the output of the conversion means
Of the carrier detected as
Before and after the pilot signal is not disturbed
5. Interpolation from a signal is described in claim 2 or 4.
On-board OFDM receiver. 6. The interference detection means is characterized in that the fast Fourier transform is used.
Error detecting means for detecting the difference between the amplitude of each pilot signal output from the converting means and the average value of the amplitude of each pilot signal in each pilot signal unit, and the error signal obtained by this means in each pilot signal unit Error mean by integrating with
An integrating means for obtaining a value and an averaging means for obtaining an average value of all pilot signals from an average value of errors of each pilot signal unit obtained by this means are provided, and reception is performed based on an averaged result of all pilot signals. C / N of OFDM signal
5. Any one of claims 1 to 4 is characterized in that
Or the OFDM receiver described above. 7. The jamming detection means is the fast Fourier transform.
Error detecting means for detecting the difference between the amplitude of each pilot signal output from the converting means and the average value of the amplitude of each pilot signal in each pilot signal unit, and the error signal obtained by this means in each pilot signal unit Error mean by integrating with
An integrating means for obtaining a value, an averaging means for obtaining an average value of all pilot signals from an average value of errors of each pilot signal unit obtained by this means, a result obtained by this means and the error signal for each pilot signal A comparison means for comparing the results of integration in units is provided, and the frequency is based on the result of the comparison.
The OFD according to any one of claims 1 to 4, characterized in that a carrier that has been disturbed by number selectivity is detected.
M receiver. 8. The interference detecting means , when an analog television broadcasting signal is transmitted in the same band as the OFDM transmission signal , disturbs the luminance carrier, the sound carrier and the color signal carrier around the analog television broadcasting signal. The pilot signal states of the band that is susceptible to interference and the band that is less susceptible to interference are compared, and from this comparison result,
Preventing frequency selectivity from analog television broadcast signals
Claims for detecting damaged carriers
The OFDM receiver according to any one of claims 1 to 4 . 9. The OFD from the reception antenna output.
A channel selecting means for selecting an M transmission signal.
The OFDM receiver according to claim 1 or 2. 10. A pilot signal is periodically transmitted to a plurality of carriers.
Orthogonal Frequency Division Multiplexing with a signal inserted (hereinafter, OFDM)
In an OFDM receiving method for receiving a transmission signal, a quadrature detection process for quadrature detection of the OFDM transmission signal and a quadrature detection output obtained in this process are transformed from a time domain to a frequency domain by a fast Fourier transform to obtain a pilot signal for each carrier. And a fast Fourier transform process for obtaining symbol data, a demodulation process for equalizing amplitude and phase based on a pilot signal to obtain demodulated data for the symbol data of each carrier obtained in this process, and the fast Fourier transform means. An interference detection step of detecting a carrier that has received frequency-selective interference from the obtained pilot signal, and an error correction step of performing error correction on the demodulated data obtained by the demodulation step, wherein the error correction step is , When a carrier that has been interfered with frequency selectivity is detected in the interference detection process, OFDM receiving method, characterized in that it comprises the erasure correction process for performing error correction by erasure process the data carrier harmed. 11. A pilot signal is periodically transmitted to a plurality of carriers.
Orthogonal Frequency Division Multiplexing with a signal inserted (hereinafter, OFDM)
In an OFDM receiving method for receiving a transmission signal, a quadrature detection process for quadrature detection of the OFDM transmission signal and a quadrature detection output obtained in this process are transformed from a time domain to a frequency domain by a fast Fourier transform to obtain a pilot signal for each carrier. And a fast Fourier transform process for obtaining symbol data, a demodulation process for obtaining demodulated data by equalizing amplitude and phase based on a pilot signal for the symbol data of each carrier obtained in this process, and the fast Fourier transform process. An interference detection process of detecting a carrier that has received frequency selective interference from the obtained pilot signal, and an error correction process of performing error correction on the demodulated data obtained by the demodulation process, the demodulation process comprising: If a carrier that is interfered with by frequency selectivity is detected in the interference detection process, interference is detected. It is characterized in that it comprises an interpolation step of interpolating the pilot signal of the received carrier with another pilot signal which is not disturbed, and equalizes the amplitude and phase of the symbol data based on the pilot signal interpolated by this means. OFDM reception method.