JP7093091B2 - Frequency corrector, demodulator circuit, radio, and frequency correction method - Google Patents

Description

The present invention relates to a symbol correction technique performed in a receiver using a digital modulation scheme.

In the receiver of the digital communication system, the communication performance is improved by performing frequency correction of the carrier frequency (including the subcarrier frequency).

Such a technique is described in, for example, Patent Document 1. Patent Document 1 discloses a technique for performing frequency correction for wireless communication. It is described in Patent Document 1 that a frequency-corrected sample is obtained by removing a frequency error from the sample in the receiver. It is also explained that there is a residual error in the frequency error estimation, that a phase error occurs in the sample frequency-corrected by the residual error, and that the performance of wireless communication may deteriorate due to the phase error. Further, Patent Document 1 describes an invention for correcting a phase error of a data symbol. It is suggested that the frequency error is caused by the difference in oscillator frequency between the transmitter and the receiver, the Doppler shift, and the like.

Further, Patent Document 2 also describes a technique for estimating a frequency error on the receiver side, performing frequency error correction, and then correcting the phase error.

In some current communication systems, pilot symbols are sequentially inserted so as to sandwich the data symbol group in the transmitter, and the frequency correction value of the data symbol group is calculated using a plurality of pilot symbols in the receiver. More specifically, the receiver calculates the phase shift amount of each pilot symbol from the received plurality of pilot symbols, and calculates the frequency correction value of the data symbol group by taking the average.

Patent Document 3 describes a method of calculating the frequency correction value of a data symbol using a plurality of pilot symbols in a receiver and correcting the frequency of the carrier of the data symbol.

Japanese Unexamined Patent Publication No. 2012-182801 Japanese Unexamined Patent Publication No. 09-307525 Japanese Unexamined Patent Publication No. 2001-339363

In the method of calculating the frequency correction value of a data symbol using a plurality of pilot symbols in a receiver such as Patent Document 3, one of the pilot symbols averaged by spatial noise and fading is greatly distorted as compared with other pilot symbols. In that case, the average value is greatly pulled by the amount of deviation of the pilot symbol, and the error of the frequency correction value becomes large.

Further, in the methods of Patent Document 1 and Patent Document 2, the phase difference at the corresponding symbol determination point between the ideal signal and the measurement signal is obtained after frequency error correction, and the phase error is corrected. In the phase error estimation for each symbol and the phase error correction after the frequency error correction (frequency error estimation), the circuit scale, the consumption of arithmetic resources, the power consumption, and the like become large.

Further, when communicating in a narrow band in which the allocated communication band or the communication band used is limited, the radio frame is configured with a small number of pilot symbols. In this case, the influence of each pilot symbol is relatively large, so a method for calculating a more accurate frequency correction value is desired. On the other hand, in the correction methods of Patent Document 1 and Patent Document 2, the circuit scale, the consumption of arithmetic resources, the power consumption, and the like become large.

The present invention has been made in view of the above problems, and as a method of frequency correction using a plurality of pilot symbols, a frequency corrector, a demodulation circuit, a radio, and a frequency corrector, a demodulation circuit, and a radio, which perform frequency correction with a low calculation amount and good accuracy. And to provide a frequency correction method.

The frequency corrector according to the embodiment of the present invention acquires the phase information for each pilot symbol and stores it in the memory, and complex-multiplies the data symbol for each data symbol a plurality of times according to the modulation method in a pseudo manner. Each pilot signal is generated, the phase information of each pseudo pilot signal for each generated symbol is acquired and stored in the memory, and the phase of each of the pseudo pilot signals is stored together with the phase information group of the pilot symbol stored in the memory. It is characterized by including a frequency correction value derivation unit that refers to an information group and derives a frequency correction value by taking an average, and a frequency correction unit that corrects a deviation of an input signal based on the frequency correction value. do.

Further, the demodulation circuit according to the embodiment of the present invention is characterized by including the frequency corrector.

Similarly, the radio device according to the embodiment of the present invention is characterized by including a demodulation circuit including the frequency corrector.

Further, in the frequency correction method using the frequency corrector according to the embodiment of the present invention, the phase information for each pilot symbol is acquired and accumulated, and the data symbol is complex-multiplied multiple times according to the modulation method for each data symbol. Pseudo-pilot signals are generated respectively, the phase information of each pseudo-pilot signal for each generated symbol is acquired and accumulated, and the phase information group of the accumulated pilot symbols and the phase information group of the pseudo-pilot signal are referred to. Then, the average is taken to derive the frequency correction value, and the deviation of the input signal is corrected based on the frequency correction value.

According to the present invention, as a method of frequency correction using a plurality of pilot symbols, it is possible to provide a frequency corrector, a demodulation circuit, a radio, and a frequency correction method capable of performing frequency correction with a low calculation amount and good accuracy.

It is a block diagram which shows the frequency corrector 1 of one Embodiment. It is a flowchart which shows the frequency correction process of the frequency corrector 1 of one Embodiment. It is explanatory drawing which shows one configuration example of the demodulator including the frequency corrector 1 and the frame format example. It is a block diagram which shows one configuration example of a frequency corrector 1. It is explanatory drawing which shows the received symbol map of QPSK and the received symbol map after multiplication calculation. It is explanatory drawing which shows the order and time series of the phase data of a pilot signal and a pseudo pilot signal. It is explanatory drawing which shows the simulation result when Eb / N0 calculated the frequency correction value of 10dB. It is explanatory drawing which shows the simulation result of the frequency correction value when Eb / N0 is close to the ideal state of 100 dB.

An embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the frequency corrector 1 of the embodiment.

The frequency corrector 1 shown in FIG. 1 includes a frequency correction value derivation unit 10 and a frequency correction unit 20 as a part of a demodulation circuit of a receiver (radio device). The frequency corrector 1 receives the symbol string, calculates the frequency correction value by the frequency correction value derivation unit 10, and frequency-corrects and outputs the symbol string by the frequency correction unit 20. The front circuit and the rear circuit of the frequency corrector 1 may adopt an existing circuit configuration suitable for the communication method.

The frequency correction value derivation unit 10 receives the pilot signal symbol (pilot symbol) and the data signal (data symbol) included in the symbol string, and derives the frequency correction value with reference to each symbol as described later. .. Further, the frequency correction unit 20 frequency-corrects the input signal based on the frequency correction value derived by the frequency correction value derivation unit 10.

The frequency correction value derivation unit 10 first acquires phase information for each pilot symbol. At the same time, the frequency correction value derivation unit 10 complex-multiplies the IQ data of each symbol for each symbol input as a data section a plurality of times according to the modulation method implemented on the transmitter side, and performs a pseudo pilot signal (1 point). (Signals converged on) are generated respectively. Next, the frequency correction value derivation unit 10 acquires the phase information of each of the pseudo pilot signals for each generated symbol.

In M-PSK (M-Phase-Shift Keying) (M = 4 for QPSK (Quadrature Phase Shift Keying), M = 8 for 8PSK), the self-symbol is complex (M-1) times. When multiplied, it converges to one point. The phase information of the corresponding symbol is acquired by using this convergence point as a pseudo pilot signal.

In the process so far, the frequency correction value derivation unit 10 has the phase information group of the pilot symbol and the phase information for each symbol input as the data section obtained by generating the pseudo-pilot signal from the symbol string sequentially input. Get a swarm.

Next, the frequency correction value derivation unit 10 derives the frequency correction value by referring to the phase information group for each symbol input as the data section together with the phase information group of the pilot symbol.

In this way, the frequency correction value derivation unit 10 uses the data symbol of the data section sandwiched between the pilot symbols in the process of calculating the frequency correction value based on the phase of the pilot symbol input as the pilot signal, and is a pseudo pilot. Generate a signal and get its phase value. Then, the frequency correction value derivation unit 10 calculates the frequency correction value by averaging an arbitrary period with reference to the phase values of each pilot signal and the pseudo pilot signal according to the input timing of each symbol. This arbitrary period may be, for example, between one pilot symbol or between a plurality of pilot symbols. Further, the number of pseudo pilot signals generated can be at least one between pilot symbols, and the maximum number of generated pseudo pilot signals can be up to the number of data symbols. By increasing the number of samples, the frequency error can be averaged with a larger number of samples, and the influence can be reduced even when noise is added to a specific pilot signal, for example. Further, the averaging may be performed by using, for example, the least squares method. In the case of averaging by the least squares method, a straight line approximation may be derived by referring to the time series of each symbol and the phase transition of each symbol, and the slope of the straight line may be output as a frequency correction value.

The frequency correction unit 20 corrects the frequency based on the frequency correction value derived by the frequency correction value derivation unit 10. This corrects the deviation of the input signal.

With the above configuration, a frequency corrector capable of performing frequency correction with a low calculation amount and good accuracy can be obtained as a method of frequency correction using a plurality of pilot symbols.

The frequency corrector 1 may be configured as a dedicated circuit or may be configured by using a microcomputer. FIG. 2 is a flowchart showing a frequency correction process of the frequency corrector 1 of the embodiment.

The frequency corrector 1 (frequency correction value derivation unit 10) receives the symbol string and detects the phase value of the pilot symbol (S101).

The frequency corrector 1 also multiplies the data symbols of the received symbol strings by the number of times according to the modulation method to generate a pseudo-pilot signal, and detects the phase value of the multiplied symbol data (S102).

The frequency corrector 1 calculates the frequency correction value by referring to the phase value of the pseudo pilot signal together with the phase value of the pilot signal every arbitrary period (S103).

The frequency corrector 1 (frequency correction unit 20) frequency-corrects the symbol string using the frequency correction value calculated for each arbitrary period (S104).

In this way, the frequency corrector 1 also provides a sample point for deriving the frequency correction value in the data symbol section, and derives an accurate frequency correction value.

As the frequency correction method for each symbol, an existing method may be used. Further, as the symbol string to be corrected, the frequency correction value may be applied to the derived data symbol of an arbitrary period according to the data delay allowance or the like, or the frequency correction derived to the data symbol of the next arbitrary period may be applied. You may want to apply the value.

By operating the frequency correction value derivation unit 10 as described above, even if the pilot signal used for frequency correction in the radio frame cannot be sufficiently secured, the modulation side can be changed in the demodulation process. It is possible to calculate a highly accurate frequency correction value from the existing received radio wave.

As a result, as a method of frequency correction using a plurality of pilot symbols, it is possible to provide a frequency correction method capable of performing frequency correction with a low calculation amount and good accuracy.

Next, the present invention will be described by showing a configuration example of the demodulator and the frequency corrector.

FIG. 3 is an explanatory diagram showing a configuration example and a frame format example of the demodulator including the frequency corrector 1. FIG. 4 is a block diagram showing a configuration example of the frequency corrector 1.

The demodulator shown in FIG. 3A includes an analog receiver 2, an orthogonal demodulator 3, a band limiting filter 4, a synchronous word detector 5, a frequency corrector 1, a symbol timing detector 6, and a symbol / bit converter 7. , Consists of a frame remover 8. Further, in the frequency corrector 1 shown in FIG. 4, the frequency correction value derivation unit 10 is approximated by the phase conversion unit 11, the first storage unit 12, the complex multiplication unit 13, the phase conversion unit 14, the second storage unit 15, and the like. It is composed of a linear calculation unit 16. In the frame format shown in FIG. 3B, nine data symbols, which are user data, are arranged in each DATA section between pilot signals (pilot symbols).

In the demodulator, AGC (Automatic Gain Control) is performed by the analog receiver 2, the IQ data output from the orthogonal demodulator 3 is captured in packet units, passed through the band limiting filter 4, and then the synchronous word detector 5 is used. Detects the reference synchronization word with. Then, the demodulator corrects the frequency shift component of the next incoming IQ data with the frequency corrector 1, extracts the data at the symbol timing with the symbol timing detector 6, and transfers it to the symbol / bit converter 7. And convert it to bit data. Finally, the demodulator removes the extra frame by the frame remover 8 and outputs it as user data.

The frequency corrector 1 converts IQ data for the pilot symbol of the input symbol string into phase information by the phase conversion unit 11, stores the converted phase information in the first storage unit 12, and approximates the stored phase information group. Input to the linear calculation unit 14. At the same time, in the frequency corrector 1, the IQ data of the data symbol of the input symbol string is multiplied by the complex multiplication unit 13 for the number of times based on the modulation method. Then the IQ data will converge to one point. The frequency corrector 1 uses this converged IQ data as a pseudo pilot signal. The frequency corrector 1 converts the converged IQ data into phase information by the phase conversion unit 14, stores the converted phase information in the second storage unit 15, and inputs the stored phase information group to the approximate linear calculation unit 16. do. Then, the frequency corrector 1 calculates the slope of the approximate straight line with respect to the phase information group by the approximate straight line calculation unit 16 by the least square method. The IQ data input to the frequency correction unit 20 is corrected using the slope as the calculation result as the frequency deviation component.

The slope of the straight line approximation by the least squares method can be calculated using Equation 1. N is the number of symbols for linear approximation, X is the symbol position on the frame, and Y is the phase information.

Here, the operation of the frequency correction value derivation unit 10 will be described in detail using the QPSK modulation method (M = 4) as an example. FIG. 5 is an explanatory diagram showing a received symbol map of QPSK and a received symbol map after multiplication calculation.

The phase conversion unit 11 converts the IQ data of the pilot symbol from the input IQ data of the frequency corrector 1 into sequential phase information, respectively.

In parallel, the complex multiplication unit 13 complex-multiplies the self-symbol from the input IQ data 3 (M-1) times. Then, the QPSK symbol divided into four points as shown in FIG. 5 (a) converges to one point as shown in FIG. 5 (b). Next, the phase conversion unit 14 converts IQ data converged to one point into successive phase information.

The approximate linear calculation unit 16 arranges and averages each phase data of each pseudo-pilot symbol in which each phase data of each pilot signal is shifted by one sample. At this time, in the approximate linear calculation unit 16, since each pseudo pilot symbol has its phase multiplied by (M-1) by the complex multiplication process (the frequency shift component is also multiplied by (M-1)), the modulation method is used. The phase value is divided based on the number of times (M-1) multiplied according to.

In the explanatory diagram shown in FIG. 6A, when each phase data of the pilot symbol group is A, B, C, D, E, F, G, the phase data group shifted by one sample is A + 1, B + 1, C + 1, D + 1, E + 1, F + 1, G + 1, 2 sample staggered phase data groups A + 2, B + 2, C + 2, D + 2, E + 2,F + 2, G + 2, similarly, a phase data group shifted by 3 to 9 samples is created to visualize the arrangement.

The explanatory diagram shown in FIG. 6B shows a state in which the phase data of the pilot signal and the pseudo-pilot signal are arranged in time series. In this way, the phase information groups of the pilot signal and the pseudo pilot signal are arranged at equal intervals.

For the phase information groups arranged at equal intervals according to this time series, linear approximation is performed for each phase data group, and the slope of each approximate straight line is averaged. This makes it possible to calculate a highly accurate frequency correction value.

In this way, the pilot symbol positions on the wireless frame are A, B, C ..., respectively, and A + 1, B + 1, C + 1 ... A + 2, B + 2, C + 2. A good frequency correction value can be obtained by defining as follows and using each data symbol, performing linear approximation for each data symbol group according to the distance from the pilot signal, and averaging the slopes of each. .. As a result, even if the C / N (Carrier to Noise Ratio) deteriorates, the error in the frequency shift calculation result can be reduced.

FIG. 7 shows the calculation result (a) and the calculation of this method when the frequency correction value is calculated only by the pilot symbol for the reception value of Eb / N0 (energy per bit to noise power spectral density ratio) of 10 dB as an example. It is a simulation result which shows the result (b). Note that FIG. 8 shows the calculation result of the frequency correction value when Eb / N0 is close to the ideal state of 100 dB. The formula shown in the upper right of the figure is the straight line formula of the straight line approximation result, and the coefficient of the X term indicates the slope.

As shown in FIG. 7A, when the frequency correction value was calculated using only the pilot symbol, y = 0.0263x + 0.1244. On the other hand, in this method, y = 0.0205x + 0.3156 was calculated. When this slope is compared with y = 0.021x + 0.0018, which shows the frequency correction value (slope) when the slope is close to the ideal state shown in FIG. 8, it can be understood that this method is closer to the ideal state.

Since the frequency correction value is calculated when the number of samples is small only with the pilot symbol, the error of the calculated value of the frequency correction value becomes larger than the result of the ideal value due to the influence of noise. As a result, when Eb / N0 deteriorates, frequency correction causes the BER (Bit Error Rate) to deteriorate.

In this method, complex multiplication is performed (M-1) times according to M of the M-PSK communication method, and a pseudo-pilot signal is generated so that all symbols can be regarded as known symbols, and the frequency correction value is calculated. Derived.

In addition to the linear approximation of the pilot symbol group, the linear approximation is performed for the data symbol group in the same manner, and the frequency correction value is derived from the slope of the straight line. The number of samples can be simply increased by the data symbol at the maximum. Looking at the results, it can be seen that this method is closer to the ideal value.

As described above, the frequency corrector to which the present invention is applied can perform frequency correction with a low calculation amount and good accuracy as a method of frequency correction using a plurality of pilot symbols. Similarly, according to the present invention, as a method of frequency correction using a plurality of pilot symbols, it is possible to provide a demodulation circuit, a radio, and a frequency correction method capable of performing frequency correction with a low calculation amount and good accuracy.

The present invention has been described by exemplifying embodiments. However, the specific configuration of the present invention is not limited to the above-described embodiment, and is included in the present invention even if there are changes to the extent that the gist of the present invention is not deviated. For example, changes such as separation and merging of the block configuration of the above-described embodiment and replacement of procedures are free as long as the gist of the present invention and the functions described are satisfied, and the above description does not limit the present invention.

In addition, some or all of the above embodiments may also be described as follows. The following notes do not limit the present invention in any way.
[Appendix 1]
In the process of calculating the frequency correction value based on the phase of the pilot symbol input as a pilot signal,
While acquiring the phase information for each pilot symbol,
The IQ data for each symbol input as a data interval is multiplied multiple times according to the modulation method to generate a pseudo-pilot signal, and the phase information of each pseudo-pilot signal for each generated symbol is acquired.
A frequency correction value derivation unit that derives a frequency correction value by referring to the phase information group for each symbol input as a data section obtained by generating a pseudo pilot signal together with the phase information group of the pilot symbol, and
A frequency correction unit that corrects the frequency based on the frequency correction value derived by the frequency correction value derivation unit, and a frequency correction unit.
A frequency corrector characterized by being equipped with.

[Appendix 2]
A pilot signal phase conversion unit that acquires the phase information of the pilot symbol from the pilot symbol input as the pilot signal, and
A complex multiplication unit that multiplies and converges the IQ data of the input data symbol by the number of times based on the modulation method,
A data signal phase conversion unit that converts IQ data of converged data symbols into phase information,
An approximate straight line calculation unit that calculates the slope of the approximate straight line indicated by the phase information of the pilot symbol and the phase information of the data symbol as a frequency correction value indicating the frequency shift component.
A frequency correction unit that frequency-corrects the data symbol input based on the frequency correction value calculated by the approximate straight line calculation unit, and a frequency correction unit.
A frequency corrector characterized by being equipped with.

[Appendix 3]
When deriving the frequency correction value, the phase information of each pseudo pilot signal for each generated symbol is divided by the phase value based on the number of times it is multiplied according to the modulation method, and then added to the phase information group of the pilot symbol. The frequency corrector according to Appendix 1 or 2, wherein the frequency correction value is calculated.

[Appendix 4]
When deriving the frequency correction value, for each phase information of the pseudo pilot signal for each generated symbol, in chronological order between the phase information of any pilot symbol and the phase information of the next pilot symbol, Addition that the phase information of the pseudo pilot signal obtained by dividing the phase value based on the number of times multiplied according to the modulation method is inserted at the position shifted by an arbitrary number of symbols to derive the approximate straight line of the least square method. The frequency corrector according to any one of 1 to 3.

[Appendix 5]
Addendum 1 characterized in that the phase information of the pseudo-pilot signal is generated for all the symbols input as the data section, and the frequency correction value is derived from the average of the gradients of the pilot signal and the pseudo-pilot signal arranged at equal intervals. The frequency corrector according to any one of 4 to 4.

[Appendix 6]
For the symbol in the middle of the data section between the pilot symbols, the phase information of the pseudo pilot signal is generated, and the frequency correction value is derived from the average of the gradients of the pilot signal and the pseudo pilot signal arranged at equal intervals. The frequency corrector according to any one of Supplementary note 1 to 4, which is a feature.

[Appendix 7]
Pseudo-pilot signal phase information is generated for all the symbols input to multiple data sections, and the phase information group of the data symbols of multiple data sections is acquired for each shift amount from each pilot symbol, and from the pilot signal. Addition that each linear approximation line is calculated from the phase information group of data symbols having the same shift amount, and the slope of the straight line obtained by averaging the linear approximation lines of each shift amount is calculated as a frequency correction value. The frequency corrector according to any one of 1 to 4.

[Appendix 8]
A demodulation circuit including the frequency corrector according to any one of Supplementary note 1 to 7.

[Appendix 9]
A radio device including a demodulation circuit including the frequency corrector according to any one of Supplementary note 1 to 7.

[Appendix 10]
The phase information for each pilot symbol input as a pilot signal is acquired, and the phase information is acquired.
The IQ data for each symbol input as a data interval is multiplied multiple times according to the modulation method to generate a pseudo-pilot signal, and the phase information of each pseudo-pilot signal for each generated symbol is acquired.
The frequency correction value is derived by referring to the phase information group for each symbol input as the data section obtained by generating the pseudo pilot signal together with the phase information group of the pilot symbols.
A frequency correction method using a frequency corrector, which comprises performing frequency correction based on a derived frequency correction value.

The present invention can be used for TDMA (Time Division Multiple Access) communication type radios and demodulators in MSK (Minimum Shift Keying) modulation and QAM (Quadrature Amplitude Modulation) modulation.

1 Frequency corrector 10 Frequency correction value derivation unit 11 Phase conversion unit (for pilot signal)
12 First storage unit 13 Complex multiplication unit 14 Phase conversion unit (for data signals)
15 Second storage unit 16 Approximate straight line calculation unit 20 Frequency correction unit

Claims (8)

The phase information for each pilot symbol is acquired and stored in the memory, and the data symbol is complexly multiplied multiple times according to the modulation method to generate a pseudo pilot signal for each data symbol, and the pseudo pilot signal is generated for each generated symbol. Each phase information of the pilot signal is acquired and stored in the memory, the phase information group of the pilot symbol stored in the memory is referred to, and each phase information group of the pseudo pilot signal is referred to, and the average is taken for frequency correction. The frequency correction value derivation part that derives the value and the
A frequency correction unit that corrects the deviation of the input signal based on the frequency correction value, and
A frequency corrector characterized by being equipped with. A pilot signal phase converter that acquires the first phase information from the pilot symbol,
A first storage unit that stores the first phase information, and
A complex multiplication unit that converges the data symbol by multiplying the data symbol by the number of times based on the modulation method.
A data signal phase conversion unit that converts the converged data symbol into the second phase information,
A second storage unit that stores the second phase information,
An approximate straight line calculation unit that calculates and obtains a frequency correction value indicating a frequency shift component by taking an average using the first phase information and the second phase information.
A frequency correction unit that corrects the deviation of the input signal based on the frequency correction value, and
A frequency corrector characterized by being equipped with. When deriving the frequency correction value, the phase information of each pseudo pilot signal for each generated symbol is divided by the phase value based on the number of complex multiplications according to the modulation method, and then the phase information group of the pilot symbol is used. The frequency corrector according to claim 1, further comprising calculating a frequency correction value. When deriving the frequency correction value, for each phase information of the pseudo pilot signal for each generated symbol, in chronological order between the phase information of any pilot symbol and the phase information of the next pilot symbol, It is characterized by inserting the phase information of the pseudo-pilot signal obtained by dividing the phase value based on the number of complex multiplications according to the modulation method at the position shifted by an arbitrary number of symbols to derive the approximate straight line of the least square method. The frequency corrector according to claim 3. Pseudo-pilot signal phase information is generated for all the symbols input to multiple data sections, and the phase information group of the data symbols of multiple data sections is acquired for each shift amount from each pilot symbol, and the phase information from the pilot signal is obtained. A claim characterized in that each linear approximation line is calculated from a phase information group of data symbols having the same shift amount, and the slope of a straight line obtained by averaging the linear approximation lines of each shift amount is calculated as a frequency correction value. Item 3. The frequency corrector according to Item 3. A demodulation circuit including the frequency corrector according to any one of claims 1 to 5. A radio device comprising the demodulation circuit according to claim 6. Acquire and accumulate phase information for each pilot symbol,
For each data symbol, the data symbol is complexly multiplied multiple times according to the modulation method to generate a pseudo-pilot signal.
The phase information of each pseudo pilot signal for each generated symbol is acquired and accumulated, and then stored.
The frequency correction value is derived by taking the average by referring to each phase information group of the pseudo pilot signal together with the phase information group of the accumulated pilot symbol .
A frequency correction method using a frequency corrector, which corrects a deviation of an input signal based on the frequency correction value.

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