JP2003264527A - Device and method for detecting ofdm frequency error, and ofdm receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a narrowband frequency error included in a received signal in a segment type OFDM (orthogonal frequency division multiplexing) standard with no fixed pilot existing. <P>SOLUTION: A signal for one symbol is inputted from an A/D converted OFDM reception signal to a narrowband frequency synchronous circuit 12. A signal extractor 121 extracts a signal of the latter half within a guard interval and a signal of the copy source of the signal from the signal for one symbol. Next, a converter 122 calculates a complex conjugate with respect to the signal of the copy source, and a multiplier 123 individually multiplies the complex conjugate and a signal within a corresponding guard interval. The respective multiplication results are added, an average value is then calculated, and a narrowband frequency error is detected on the basis of the phase of the average value. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrow band frequency error detection algorithm in the development of an LSI for an OFDM terrestrial digital television broadcast receiver.

[0002]

BACKGROUND OF THE INVENTION <1. Outline of OFDM Transmission> As a transmission method for terrestrial digital broadcasting, an OFDM method that multiplex-transmits hundreds to thousands of orthogonal carrier waves (subcarriers) within a certain band has been adopted in Japan, Europe and the like. ing. "Subcarriers are orthogonal to each other" means that the peak point of the spectrum of an arbitrary subcarrier always coincides with the zero point of the spectrum of another subcarrier. Such an OFDM method has an advantage that frequency utilization efficiency is very high and it is resistant to fading interference that occurs during mobile reception. Further, the OFDM method has an advantage that it is less susceptible to the multipath phenomenon in which radio waves are reflected by obstacles such as high-rise buildings and mountains and arrive at the receiver after being delayed from a plurality of routes.

Such an OFDM system is being adopted not only for digital terrestrial broadcasting, but also for wire communication using telephone lines and power lines, wireless communication such as wireless LAN (Local Area Network), and the like.

As shown in FIG. 4, a symbol signal modulated by the OFDM system is composed of effective symbols including data and control signals and a guard interval for reducing the influence of multipath. The guard interval is set at the beginning of each symbol signal and is a copy of the end of the effective symbol. Here, the leading side of the guard interval means the temporal leading side, and in terms of FIG. 4, the left side of the figure is the leading side.

If the delay time of the reflected wave due to multipath is within the guard interval period Tg, it is possible to extract data for one complete symbol without the influence of intersymbol interference (ISI). Incidentally, the guard interval period Tg is normally 1/4, 1/8, or 1/8 of the effective symbol period Tu.
It is set to either 1/16 or 1/32.

In the OFDM transmission having such characteristics, the transmission data of the OFDM transmission is IDF on the transmitting device side.
An OFDM symbol is obtained by being T (inverse Fourier transform). Then, an analog OFDM symbol is transmitted to the receiving device side by D / A converting this OFDM symbol.

Here, the transmission data is x (k) (k = 0,
1, ... N-1). The transmission data x (k) is I
When modulated by DFT (Inverse Fourier Transform), it becomes an OFDM symbol signal X (n) as shown in Formula 1.

[0008]

[Equation 1]

However, in the equation 1, k is a carrier number, N is the total number of carriers, and n is a discrete index in the time direction. Here, assuming that the sampling time interval is T, the relationship of Equation 2 is established with respect to the time t.

[0010]

[Equation 2]

Therefore, the OFDM symbol signal X (n) expressed by the equation 1 is D / s at the sampling time interval T.
Analog OF shown by the equation 3 by A conversion
The DM symbol signal X (t) is obtained.

[0012]

[Equation 3]

F ₀ in the equation 3 represents the reciprocal of the symbol period NT, that is, the subcarrier interval, as shown in the equation 4.

[0014]

[Equation 4]

When a frequency error occurs in the transmission line, the transmission signal expressed by the equation (3) becomes X _{r expressed by the} equation (5).
(T). The frequency error is caused by the Doppler effect of the transmission path and the error of the tuner on the receiving side.
The narrow band frequency error is a relatively small frequency error within the subcarrier interval.

[0016]

[Equation 5]

In Equation 5, Δf represents an analog frequency error. When the received signal in which the frequency error shown by the formula 5 has occurred is converted into a digital signal by A / D conversion, the received signal X _r (n) shown by the formula 6 is obtained.

[0018]

[Equation 6]

Here, since attention is paid to the case where the analog frequency Δf is a frequency smaller than the subcarrier interval f ₀ , that is, the case where the frequency error is a narrow band, Δk can be defined as in the equation (7). .

[0020]

[Equation 7]

Therefore, by using the equation (7),
The received signal X _r (n) of the equation 6 can be transformed into the equation 8.

[0022]

[Equation 8]

When an attempt is made to restore a signal modulated by FFT conversion from the received signal X _r (n) in which such a narrow band frequency error has occurred, the following equation 9 is obtained.

[0024]

[Equation 9]

In the equation (9), the first term on the right side is the desired signal and the second term is the ICI (Inter-Channel Interface). It can be seen that amplitude attenuation and phase rotation also occur in the desired signal. As a practical standard, Δk <1% is required, but since the actual narrowband frequency error can reach 30%, it is necessary to detect such a frequency error, and 1% or less is corrected by correction. Need to be kept to.

[0026]

As described above, it is necessary to detect and correct the narrow band frequency error, but in the European standard, it is possible to detect the frequency error from the phase of the CP (pilot signal). is there. However, that method cannot be used in Japanese standards. The reasons are the following two points.

(1) Since the Japanese standard has a segment structure, unlike the European standard, there is no pilot signal with a fixed insertion position. FIG. 5 is a diagram showing an OFDM format on the transmission spectrum. As described above, in the Japanese-standard OFDM format, one symbol signal is composed of 13 segments, and further, the segments are composed of two types of differential modulation segments and synchronous modulation segments. Depending on the types of the segments, pilots are arranged. Because it is different.

(2) A / D error is also included in the phase of the pilot signal such as CP. European standard OFDM
In, it is possible to eliminate the A / D error component by utilizing the symmetry of the arrangement of the CPs to be inserted, but since there is no symmetrically arranged pilot in the Japanese standard, the A / D The error cannot be removed.

Therefore, in view of the above problems, it is an object of the present invention to provide an algorithm for detecting a narrow band frequency error in OFDM transmission of Japanese standard.

[0030]

In order to solve the above-mentioned problems, an invention according to claim 1 is an apparatus for detecting a narrow band frequency error which does not exceed a subcarrier interval from a received OFDM (orthogonal frequency division multiplexing) signal. And a) OFDM
A symbol signal obtaining means for obtaining a signal for one symbol from the received signal; and b) obtaining a signal for one symbol,
Signal extraction means for extracting a signal within the guard interval (hereinafter referred to as a first signal) and a signal within an effective symbol (hereinafter referred to as a second signal) that is a duplication source of the first signal; C) the first extracted by the signal extracting means
And multiplying means for multiplying the complex conjugate value of one of the second signal and the signal value of the other signal, and d) the frequency error of the narrow band from the phase of the multiplied value calculated by the multiplying means. And means for acquiring.

The invention according to claim 2 is the received OFDM.
A device for detecting a narrow band frequency error from a (orthogonal frequency division multiplexing) signal, comprising: a) a symbol signal acquisition means for acquiring a signal for one symbol from an OFDM received signal; and b) a signal within a guard interval (hereinafter , The first signal)
And a signal within an effective symbol (hereinafter, referred to as a second signal) that is a duplication source of the first signal as one signal set, from among the signal of one symbol acquired by the symbol signal acquisition means. Signal extraction means for extracting a plurality of signal sets; and c) for each signal set extracted by the signal extraction means, a complex conjugate value of one of the first and second signals and a signal value of another signal. And d) means for calculating an average multiplication value from the multiplication values for each signal set calculated by the multiplication means, and e) means for detecting a frequency error from the phase of the average multiplication value. ,
It is characterized by including.

According to a third aspect of the present invention, in the OFDM frequency error detecting apparatus according to the first or second aspect, the symbol signal acquisition means is equivalent to one symbol from the OFDM received signal before being FFT converted. It is characterized by acquiring a signal.

The invention according to claim 4 is the frequency error detecting apparatus for OFDM according to any one of claims 1 to 3, wherein the signal extracting means is b-1) at the head side in the guard interval. Means for extracting the first signal from an area excluding a predetermined area.

According to a fifth aspect of the present invention, in the frequency error detecting apparatus for OFDM according to the fourth aspect, the predetermined area is an area of a leading side half in the guard interval, and the signal extracting means is the area. It is characterized in that the signal in the rear half of the guard interval is extracted.

According to a sixth aspect of the present invention, in the OFDM frequency error detecting apparatus according to any of the first to fifth aspects, the OFDM received signal is a signal transmitted in accordance with a segment system OFDM standard. It is characterized by

The invention according to claim 7 is the received OFDM.
(Orthogonal Frequency Division Multiplexing) A method for detecting a narrow band frequency error that does not exceed the subcarrier spacing from a signal, comprising: a)
A step of acquiring a signal for one symbol from the OFDM received signal; b) a signal within a guard interval (hereinafter referred to as a first signal); and a signal within an effective symbol that is a duplication source of the first signal ( Hereinafter, referred to as a second signal) as one signal set, and extracting a plurality of signal sets from the signal of one symbol acquired in the step a),
c) For each signal set extracted in step b),
Multiplying the complex conjugate value of one of the first and second signals by the signal value of the other signal; d) the step
c) a step of calculating an average multiplication value from the multiplication values for each signal set calculated, and e) a step of detecting a narrow band frequency error from the phase of the average multiplication value. .

An eighth aspect of the present invention is a receiver for segmented OFDM (Orthogonal Frequency Division Multiplexing) transmission, comprising the OFDM frequency error detecting device according to any one of the first to sixth aspects. Means for correcting the frequency error of the OFDM received signal based on the detection result of the narrow band frequency error by the OFDM frequency error detecting device.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

{1. Overall Configuration of OFDM Demodulator} FIG. 1 is a schematic configuration diagram of an OFDM demodulator according to an embodiment of the present invention. An RF (Radio Frequency) signal 1 transmitted from an OFDM transmitter (not shown) is received by a reception antenna 2 through a transmission path and then received by a front end processing unit 3. The front-end processing unit 3 includes a tuner that frequency-converts the RF signal 1 into an IF (Intermediate Frequency) signal, a BPF (band pass filter), a mixer that multiplies with a signal supplied from a carrier wave oscillator, an LPF (low pass filter), and the like. I'm out. The signal output from the front end processing unit 3 is A
It is input to the / D converter 4.

The A / D converter 4 converts the input signal into a digital signal at a predetermined sampling frequency. The OFDM signal converted into a digital signal is output to the serial-parallel converter 7 via the mixer 5 and the resampler 6.

Specifically, the OFDM signal output from the A / D converter 4 is corrected by the mixer 5 such as wide band and narrow band frequency errors. Then, the signal rate is adjusted by the resampler 6 and then output to the serial-parallel converter 7.

The resampler 6 performs interpolation processing and decimation on the input signal.
n) Processing and polyphase filter (polyphase f
ilter). FFT (Fast Fourier Transform) described later
Sampling frequency of FFT used in the calculator 8 and A
Since the sampling frequency of the A / D conversion in the A / D converter 4 is different, the resampler 6 uses the A / D conversion and the FF
It has a function of adjusting the disagreement between the sampling frequencies of T and T.

Further, the resampler 6 has a function for matching the FFT sampling frequency on the transmitting side and the FFT sampling frequency on the receiving side, that is, a function for eliminating a sampling error (or A / D error). ing.

On the other hand, the symbol synchronization circuit 13 detects a time shift of the symbol signal serially input from the resampler 6, and outputs the detection signal to the serial-parallel converter 7.

The serial-parallel converter 7 buffers the input symbol signal, converts it into a parallel signal in accordance with the FFT window using the detection signal, and outputs the parallel signal to the FFT calculator 8. Here, the FFT window means a time domain in which a signal is captured by the FFT calculator 8.

The FFT calculator 8 performs fast Fourier transform on the input N-point symbol signals to output N OFDM demodulated signals in the frequency domain in parallel.

In addition, the wide band frequency synchronizing circuit 11 has an FF
A wideband frequency error is detected based on the frequency component of the OFDM demodulated signal output from the T calculator 8. Here, the wideband frequency error is a large frequency error that exceeds the subcarrier interval. Then, the detection signal of the wide band frequency error is output to the mixer 5 and frequency correction is performed.

The narrow band frequency synchronizing circuit 12 which is the main part of the present invention detects a narrow band frequency error based on the symbol signal output from the serial-parallel converter 7.
Here, as described above, the narrow band frequency error is a relatively small frequency error within the subcarrier interval. Then, the detection signal of the narrow band frequency error is output to the mixer 5 and frequency correction is performed. Narrowband frequency synchronization circuit 1
The processing content of 2 will be described later.

The A / D synchronization circuit 14 has a function of detecting an A / D conversion error in the A / D converter 4 (that is, a sampling error with the transmitting side). The detection signal of the A / D conversion error is output to the resampler 6. Then, as described above, the resampler 6 uses the detection signal input from the A / D synchronization circuit 14 to correct the A / D conversion error.

Although it is possible to perform A / D synchronization processing by directly adjusting the sampling frequency in the A / D converter 4, in such a case, the circuit configuration becomes complicated and the sampling frequency is relatively high. Since the cost is high, there is a problem that noise is likely to be mixed in and the cost is likely to be large.
On the other hand, the resampler 6 has an advantage that the A / D conversion error can be corrected by digital signal processing and the circuit configuration can be simplified.

Next, the OFDM demodulated signal is output to the frame synchronization circuit 9. In the frame synchronization circuit 9,
After finding the beginning of the frame in which the 204-symbol signal is one processing block, the equalizer 10 detects this OFD.
The M demodulated signal is output after being equalized based on the pilot signal embedded in the OFDM demodulated signal.

Further, the FFT window adjusting section 15 detects the shift of the FFT window position based on the SP (Scattered Pilot) signal output from the frame synchronization circuit 9, and outputs the detection signal as F
Output to the FT calculator 8. The FFT calculator 8 finely adjusts the FFT window position based on this detection signal.

{2. Theory of Narrow Band Frequency Error Detection in the Present Invention} Next, the Japanese standard O adopted in the present invention
A narrow band frequency error detection theory applicable in FDM transmission will be described. When a narrow band frequency error has occurred, the signal before FFT conversion on the receiving side is expressed as in Equation 8.

Therefore, the equation (8) is transformed into the equation (10).

[0055]

[Equation 10]

That is, when the narrow band frequency error occurs, the received signal X (n) has an additional phase. The periodicity of the guard interval is used to remove the additional phase.

If X (n) is the data within the guard interval, X (n + N) is the signal of the copy source, so X (n) = X (n + N) holds. Therefore, when only the narrow band frequency error occurs, the equation (11) holds.

[0058]

[Equation 11]

Thus, the narrow band frequency error Δk can be detected by taking the complex conjugate product of the signal within the guard interval immediately before the FFT conversion on the receiving side and the signal of the copy source. .

However, the actual signal contains noise. That is, the expression (10) is expressed as the expression (12).

[0061]

[Equation 12]

In the equation (12), ν (n) is white noise. When there is noise, the equation (11) is expressed by the equation (13).

[0063]

[Equation 13]

Since ν (n) is white noise and has no correlation with the signal, the right three terms on the right side can be eliminated by obtaining the average E in the equation (13).
That is, it is expressed as in Expression 14.

[0065]

[Equation 14]

Even in the case where the signal contains noise, the narrow band frequency error can be easily detected. The merits of the method of detecting a narrow band frequency error using a signal within the guard interval can be summarized in the following two points.

(1) There is a merit that the accuracy is high.
As can be seen from the equations (11) and (12), the signal before the FFT conversion is mainly subjected to the disturbance, and the influence of the noise is easily removed by averaging. A / D
Although an error has occurred, only the signal within one symbol is handled, so its influence can be ignored.

For example, Δk (narrowband frequency error) = 3
0%, SNR = 5 dB, DU = 0 dB, Doppler
shift = 70 Hz, A / D shift (A / D
When the simulation was performed under a rather severe condition of (error) = 0.0001, the detected average value of 100 times was Δ.
It became k = 30.03%. That is, the variance of the detection error is 0.0087, and the frequency error can be detected with high accuracy.

(2) Since narrow band frequency error causes ICI, detection and correction are performed before FFT conversion to detect synchronization error after FFT conversion, for example,
It is also convenient for wideband frequency error detection using AC1 and TMCC signals, A / D error detection, and the like.

{3. Configuration of narrow-band frequency synchronization circuit} Fig. 2
FIG. 3 is a block configuration diagram of a narrowband frequency synchronization circuit 12 according to the exemplary embodiment. The narrow band frequency synchronization circuit 12 includes a signal extractor 121, a converter 122 for converting a complex signal into its conjugate complex signal, a multiplier 123, an adder 124, an average value calculator 125, a phase calculator 126, and a divider 127. Is equipped with.

The symbol signal (OFDM reception signal) converted into parallel data by the serial-parallel converter 7 is paralleled to the narrow band frequency synchronization circuit 1 as a signal group of 1 symbol.
Entered in 2. The symbol signals input in parallel are signals including narrow band frequency error and white noise, that is, signals represented by the equation (12).

The symbol signal input to the narrow band frequency synchronizing circuit 12 is a signal having an effective symbol length N and a guard interval length (N / G). Here, G is a guard interval coefficient, and is a number such as 4, 8, 16, 32 or the like. For example, the guard interval coefficient G
= 4, it means that a guard interval having a length of 1/4 of the effective symbol length N is added.

Therefore, the symbol signal input in parallel to the narrow band frequency synchronization circuit 12 has a symbol length {N +
(N / G)} time domain signal, but the signal extractor 1
Reference numeral 21 extracts a signal at a predetermined point necessary for establishing narrow band frequency synchronization from the symbol signal at the {N + (N / G)} point.

In this embodiment, the signal extractor 12
1 is (N + (N / G)) from the symbol signal at the point (N
A received signal within the guard interval of the / 2G point and a received signal at the (N / 2G) point at the end of the effective symbol corresponding to the received signal within the guard interval of the (N / 2G) point are extracted. I am trying.

In the present embodiment, the received signal within the guard interval to be extracted is (N / 2) from the beginning.
The reception signal at the point G) is excluded, and the reception signal at the latter half (N / 2G) point is extracted.

FIG. 3 shows, in the present embodiment, the areas of the signals extracted by the signal extractor 121 from one symbol by hatching. The number shown in the figure is an index in which the head of the guard interval is set to 1 and is attached to the received signal. If expressed by indexes, the signals extracted by the signal extractor 121 are index {(N / 2G) +1} to (N / G) and indexes {N + (N / 2G) +1} to {N +.
(N / G)}, which is the total (N / G) point signal. Here, as shown in the figure, among the extracted reception signals, the reception signals of indexes {(N / 2G) +1} to (N / G) are the signals in the A region, and the indexes {N + (N / 2G) +1}.
Let {N + (N / G)} received signals be signals in the B region.

Next, of the received signals extracted by the signal extractor 121, the received signals in the B area are input to the converters 122, 122 ... Which are arranged in parallel.
Here, in the figure, s (i) means a signal value corresponding to each index i.

The received signals in the B area are converted into converters 122 and 12
In 2 ..., The complex conjugate signal is converted in parallel. Therefore, in this embodiment, there are (N / 2G) converters 122.

.. multiplies the received signal in the A region and the complex conjugate signal in the B region corresponding to the received signal in the A region in parallel. Therefore, in the present embodiment, (N / 2
There will be G) multipliers 123. The output of each multiplier 123 corresponds to the signal value shown in the equation 13.
Alternatively, a complex conjugate signal of the signal in the A region may be calculated and the calculated value may be multiplied by the signal value in the B region.

In this way, in each of the multipliers 123, 123 ...
When the multiplication result with the complex conjugate signal of the region is output, the outputs of these (N / 2G) sets are added by the adder 124,
Further, the average value calculator 125 divides by (N / 2G) and outputs the average multiplication result. This average multiplication result corresponds to the signal value shown in Expression 14.

The average multiplication result output from the average value calculator 125 is input to the phase calculator 126, and the phase value 2πΔk is calculated. When the phase value of the average multiplication result is calculated, it is divided by (−2π) in the divider 127, so that the narrow band frequency error Δk is detected.

As described above, in the narrow band frequency error detecting method according to the present embodiment, the narrow band frequency error is detected by the simple calculation process using the signal within the guard interval and the signal which is the copy source thereof. It is possible. The narrow band frequency error Δk detected in the narrow band frequency synchronization circuit 12 is output to the mixer 5. In the mixer 5,
Correction processing is performed according to this frequency error. By performing such feedback processing, it is possible to remove the narrow band frequency error from the received signal.

As described above, in the present embodiment, received signals of indexes 1 to (N / 2G) are not extracted. The reason is that within the guard interval 1
This is because there is a high possibility that a signal of (N / 2G), that is, a signal on the head side contains a reflected wave due to the influence of multipath. Therefore, the detection accuracy is improved by excluding the part from the extraction region.

In the present embodiment, the signals in the second half of the signals within the guard interval excluding the signals in the first half are used, but this is an example. Except for the 1/3 signal, the following 2/3 signal may be used, or the rear side 1/3, 1/4, etc. signals may be used.
Further, the area from which the signal is extracted may be a separated area. The number of signals to be extracted in this way can be freely determined to some extent, but the greater the number, the higher the frequency error detection accuracy. However, along with this, the number of hardware components increases as shown in FIG. Therefore, it is better that the number of signals to be extracted is smaller from the viewpoints of downsizing the device and cost reduction.

In the segment type OFDM standard, the shortest guard interval (mode 1, G = 32)
In the case of), there are 64 pieces of data. Therefore, even if only half of the data is used to detect the frequency error, the simulation result shows that the influence on the noise removal is small.

That is, the method of extracting the signal of the second half of the guard interval as shown in this embodiment is a method in consideration of the balance between the detection accuracy of the frequency error and the reduction of the calculation amount (compact hardware). Can be said to be However, whether to focus on improving detection accuracy or to make hardware compact,
From this point of view, it is possible to freely determine the number of signals to be extracted for frequency error detection.

[0087]

As described above, according to the first aspect of the invention, the narrow band frequency error is detected by calculating the complex conjugate product of the signal within the guard interval and the signal of the copy source of the signal. Therefore, it is possible to detect a narrow band frequency error by a simple process.

According to the second aspect of the present invention, the narrow band frequency error is detected by calculating the average value of the complex conjugate products of the signals within the plurality of guard intervals and the signals of the copy source of these signals. Even in an environment where noise is generated, it is possible to detect a narrow band frequency error by simple processing.

According to the third aspect of the present invention, since the narrow band frequency error is detected in the OFDM signal before FFT conversion, it is possible to suppress the occurrence of ICI after FFT.

According to the fourth aspect of the present invention, since the frequency error is detected by excluding the signal in the area on the leading side within the guard interval, it is possible to avoid the influence of multipath and improve the detection accuracy. .

According to the fifth aspect of the present invention, the first half region within the guard interval is excluded and the signals of the second half are extracted, so that the detection accuracy is improved and the device configuration is made compact. It is possible.

According to the invention described in claim 6, by using the frequency error detecting device of the present invention in the OFDM transmission of the segment system, it is possible to easily detect the narrow band frequency error even in the Japanese standard where there is no fixed pilot. Is.

The invention according to claim 7 is a method invention, wherein a narrow band frequency is calculated by calculating an average value of complex conjugate products of signals within a plurality of guard intervals and signals from which these signals are copied. Since the error is detected, the narrow band frequency error can be detected by a simple process.

The invention described in claim 8 is an OFDM receiver provided with the frequency error detecting device of the present invention, and it is possible to detect a narrow band frequency error by a simple process.

[Brief description of drawings]

FIG. 1 is a functional block diagram of an OFDM receiving apparatus according to this embodiment.

FIG. 2 is a functional block diagram of a narrow band frequency synchronization circuit.

FIG. 3 is a diagram showing a signal region extracted from a symbol signal for frequency error detection.

FIG. 4 is a diagram showing a configuration of a symbol signal in the time direction.

FIG. 5 is a diagram showing a configuration of a symbol signal in a carrier direction.

[Explanation of symbols]

5 mixer 7 Serial-parallel converter 8 FFT calculator 12 Narrowband frequency synchronization circuit 121 Signal extractor 122 converter 123 multiplier 124 adder 125 average value calculator 126 Phase calculator 127 divider

Claims (8)

[Claims] 1. An apparatus for detecting a narrow band frequency error that does not exceed a subcarrier interval from a received OFDM (Orthogonal Frequency Division Multiplexing) signal, comprising: a) a symbol for obtaining a signal for one symbol from the OFDM received signal. A signal acquisition unit, b) a signal within a guard interval (hereinafter, referred to as a first signal) from among the acquired 1-symbol signals, and the first signal.
Signal extracting means for extracting a signal (hereinafter, referred to as a second signal) in an effective symbol which is a duplication source of the signal of c), c) the first and second signals extracted by the signal extracting means
Of the signal of one of the signals and the signal value of the other signal, and d) means for obtaining the frequency error of the narrow band from the phase of the multiplication value calculated by the multiplying means. An OFDM frequency error detection device comprising: 2. An apparatus for detecting a narrow band frequency error from a received OFDM (Orthogonal Frequency Division Multiplexing) signal, comprising: a) a symbol signal acquiring means for acquiring a signal for one symbol from the OFDM received signal; ) A signal within a guard interval (hereinafter, referred to as a first signal) and a signal within an effective symbol (hereinafter, referred to as a second signal) that is a duplication source of the first signal are set as one signal set. Signal extraction means for extracting a plurality of signal sets from the signal of one symbol acquired by the symbol signal acquisition means, and c) for each signal set extracted by the signal extraction means, the first and second signals A multiplication means for multiplying the complex conjugate value of one of the signals with the signal value of the other signal; and d) calculating an average multiplication value from the multiplication values for each signal set calculated by the multiplication means. A frequency error detecting apparatus for OFDM, comprising: a means; and e) means for detecting a frequency error from the phase of the average multiplication value. 3. The OFD according to claim 1 or 2.
In the frequency error detection device for M, the symbol signal acquisition means is O before FFT conversion.
An OFDM frequency error detection device, which acquires a signal for one symbol from an FDM received signal. 4. The frequency error detecting apparatus for OFDM according to claim 1, wherein the signal extracting means is b-1) a region excluding a predetermined region on the head side in the guard interval. And a means for extracting the first signal from the frequency error detecting apparatus for OFDM. 5. The OFDM frequency error detecting apparatus according to claim 4, wherein the predetermined area is an area of a leading half of the guard interval, and the signal extracting means is located at a rear side of the guard interval. A frequency error detection device for OFDM, characterized in that a half signal is extracted. 6. The OFDM frequency error detection device according to claim 1, wherein the OFDM received signal is a signal transmitted in accordance with a segment system OFDM standard.
Frequency error detector for DM. 7. A method for detecting a narrow band frequency error not exceeding a subcarrier interval from a received OFDM (Orthogonal Frequency Division Multiplexing) signal, the method comprising the steps of: a) obtaining a signal for one symbol from the OFDM received signal. B) A signal within the guard interval (hereinafter, referred to as a first signal) and a signal within an effective symbol (hereinafter, referred to as a second signal) that is a duplication source of the first signal are combined into one. As a signal set, a step of extracting a plurality of signal sets from the one-symbol signal acquired in the step a), and c) each signal set extracted in the step b),
Multiplying the complex conjugate value of one of the first and second signals by the signal value of the other signal, and d) averaging the multiplied values for each signal set calculated in step c). A method of detecting a frequency error for OFDM, comprising: a step of calculating a multiplication value; and e) a step of detecting a narrow band frequency error from the phase of the average multiplication value. 8. A receiver for segmented OFDM (Orthogonal Frequency Division Multiplexing) transmission, comprising: the OFDM frequency error detector according to claim 1, and the OFDM frequency error detector. Means for correcting the frequency error of the OFDM received signal based on the detection result of the narrow band frequency error by the apparatus.
DM receiver.