JP2000188580A - Ofdm receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a signal transmission rate by enhancing a processing speed of a frequency offset detection circuit. SOLUTION: A phase information generator 109 detects a phase difference depending on a quadrant to which a phase discriminated by an absolute value of a common-mode component and an absolute value of a quadrature component of a received signal before FFT processing belongs and calculates a frequency offset by subtracting phase information of the received signal from phase information of one preceding symbol. The frequency offset can be compensated by using a frequency offset calculated without multiplication processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus used for OFDM mobile communication.

[0002]

2. Description of the Related Art A receiving apparatus used for conventional OFDM mobile communication (hereinafter simply referred to as an OFDM receiving apparatus).
Will be described with reference to FIGS. 25 and 26. FIG.
Is a main block diagram showing a schematic configuration of a conventional OFDM receiving apparatus, and FIG. 26 is a schematic diagram of a frame format in wireless communication of the OFDM system.

First, the configuration of a conventional apparatus will be described with reference to FIG. The quadrature detector 2501 includes an oscillator 25 described later.
The quadrature detection process is performed on the input received signal, which is controlled by the local signal output from the input signal 13. analog·
The low-pass filters (LPF) 2502 and 2503 are
Remove unnecessary frequency components. A / D converters 2504, 2
505 converts the input analog signal into a digital signal.

[0004] Fourier transform (fast Fourier transform)
(Transform; hereinafter, referred to as FFT) circuit 25
06 performs FFT processing on the input signal, and the delay detector 2507 performs delay detection processing on the input signal. The determinator 2508 determines the differential detection signal.

[0005] The delay units 2509 and 2510 delay the input signal and output it. The complex multiplier 2511 performs complex multiplication. This complex multiplication will be described later. The memory 2512 stores the output of the complex multiplier 2511, and the oscillator 2513 outputs a local signal corrected by the output of the complex multiplier 2511.

Next, the operation of the conventional apparatus will be described. The quadrature detector 2501 performs quadrature detection processing on a received signal to obtain a baseband signal that is an analog signal. This baseband signal is supplied to LPFs 2502 and 250
3, unnecessary frequency components are removed, and the A / D converter 2
Are converted into digital signals by 504 and 2505,
It becomes a digital baseband signal.

[0007] The digital baseband signal is subjected to FFT processing by an FFT circuit 2506 to obtain a signal assigned to each subcarrier. Further, the delay detection processing is performed by the delay detector 2507,
A determination is made by 8 and a demodulated signal is obtained.

[0008] In mobile communication of the OFDM system, frequency offset compensation is necessary because the reception characteristics deteriorate significantly due to the frequency offset. Hereinafter, the frequency offset compensation will be described.

In mobile communication of the OFDM system, generally, as shown in FIG. 26, the same waveform as the last part of each symbol is inserted at the head of each symbol as a guard interval. Generally, a frequency offset is detected using the guard interval which is a known symbol.

First, a complex multiplier 251 compares a signal before FFT processing and a signal obtained by delaying the signal before FFT processing by one symbol by delay units 2509 and 2510.
1 performs complex multiplication represented by the following equation.

(Equation 1) Here, R (nT) represents phase information.
D (nT) represents a received signal, Ts represents a symbol length, Tg represents a guard interval length, and T represents a sampling period. n takes 1, 2,....

When the frequency offset Δf is present, when the guard section is compared with the last part of the effective symbol, the following equation holds because the phase is rotated by 2πΔfTs. R (nT) = | R (nT) | · exp (2πΔfTs) − Therefore, by using the frequency offset Δf, the phase rotation amount 2πΔfTs between one symbol required for frequency offset compensation can be obtained from the equation.

The frequency offset Δf is detected by using, for example, the same symbol as the phase reference symbol required for differential detection at the head of each burst without using a guard interval. May be detected from the result of complex multiplication.

As described above, in the complex multiplier 2511, the signal before the FFT processing and the signal before the FFT processing are 1
A complex signal is multiplied by the signal delayed by the symbol, and the resulting phase information R (nT) is stored in the memory 2512. The phase information R (nT) is substituted into the equation together with the frequency offset Δf, and the phase rotation amount 2πΔfTs is obtained.

The oscillator 2513 has a phase rotation amount of 2πΔfT
The local signal subjected to frequency offset compensation based on s is output to quadrature detector 2501. The quadrature detector 25 controlled by the local signal thus generated
01 performs quadrature detection processing, thereby performing frequency offset compensation.

As described above, the conventional OFDM receiver is
Deterioration of reception characteristics due to frequency offset is prevented.

[0016]

However, the conventional apparatus has the following problems. That is,
Since the processing speed of the frequency offset detection circuit is limited by the processing of the multiplier having a low processing speed, it is difficult for the frequency offset detection circuit of the conventional device employing the configuration using the multiplier to increase the processing speed. is there.

The present invention has been made in view of the above, and an object of the present invention is to provide an OFDM receiver in which the processing speed of a frequency offset detection circuit is improved and the signal transmission speed is improved.

[0018]

The gist of the present invention is to simply convert the phase difference by the quadrant to which the phase belongs based on the absolute value of the in-phase component and the absolute value of the quadrature component of the received signal, and to easily obtain the phase information of the received signal. Is calculated, and the phase information of the received signal and 1
The frequency offset is calculated by subtracting the phase information before the symbol, and the frequency offset is compensated using the calculated frequency offset.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS OFD according to a first embodiment of the present invention
An M receiving apparatus includes: a difference detection unit that detects a difference between an absolute value of an in-phase component and an absolute value of a quadrature component of a quadrature-modulated OFDM reception signal; and a reception signal in an orthogonal plane based on an output of the difference detection unit. A quadrant determining means for determining a quadrant to which a phase belongs; a phase detecting means for detecting a phase of the received signal from an output of the difference detecting means and an output of the quadrant determining means; and a detected phase and a detected phase. Frequency offset detection means for detecting the frequency offset by subtracting the phase delayed by a predetermined symbol, and frequency offset compensation means for performing frequency offset compensation on the received signal using the detected frequency offset,
Is adopted.

According to this configuration, when the frequency offset of the received signal is detected, the detection is performed by subtracting the absolute value of the I component and the Q component of the received signal and determining the quadrant to which the phase belongs. That is, since only the subtraction process is used and the multiplication process is not used, the amount of calculation required for frequency offset detection can be reduced, the processing speed can be increased, and as a result, the signal transmission speed of the OFDM receiver can be increased.

An OFDM receiver according to a second aspect of the present invention, in the first aspect, adopts a configuration in which the frequency offset detecting means has an averaging section for averaging the calculated frequency offset.

According to this configuration, since the phase error can be removed from the detected frequency offset, the detection accuracy of the frequency offset can be improved.

According to a third aspect of the present invention, in the OFDM receiving apparatus according to the second aspect, the averaging section averages only a phase of a received signal having a reception level larger than an arbitrary constant value. Take.

According to this configuration, the frequency offset when the reception level of the received signal is lower than the threshold value is determined to include an error, and is not included in the averaging process.
The detection accuracy of the frequency offset can be improved.

[0025] In the OFDM receiver according to a fourth aspect of the present invention, in the second aspect or the third aspect, the averaging section may further comprise a frequency offset exceeding an arbitrary constant value from the calculated frequency offsets. A configuration in which only the average processing is performed is adopted.

According to this configuration, the frequency offset below the threshold value is determined to include an error and is not included in the averaging process, so that the accuracy of detecting the frequency offset can be improved.

An OFDM receiver according to a fifth aspect of the present invention is the OFDM receiver according to any one of the first to fourth aspects,
The phase detection means employs a configuration having a thinning unit that reduces the number of samplings of the in-phase component and the quadrature component of the received signal after removing unnecessary frequency components.

According to this configuration, the signal processing can be sped up in order to reduce the sampling frequency.

An OFDM receiver according to a sixth aspect of the present invention is the OFDM receiver according to the second aspect, further comprising: a serial / parallel converter for converting the in-phase component and the quadrature component of the received signal into a plurality of series signals; A configuration including a phase detection unit and a quadrature component phase detection unit is employed.

According to this configuration, since the frequency offset detection can be performed by parallel processing, the signal processing speed can be increased.

An OFDM receiving apparatus according to a seventh aspect of the present invention, in the second aspect, adopts a configuration in which the phase detecting means identifies a channel of a received signal and takes in only a signal of a specific channel.

According to this configuration, since only a signal of a specific channel is used for phase detection, the amount of signals to be processed is reduced.
The processing speed can be increased, and the power consumption can be reduced.

An OFDM receiver according to an eighth aspect of the present invention is the OFDM receiver according to any one of the second to seventh aspects,
The averaging unit subtracts the current frequency offset value from the frequency offset value one symbol before, and when the result of the subtraction exceeds an arbitrary fixed value, averages the current frequency offset value. The configuration that is not used for is adopted.

According to this configuration, the frequency offset whose value is greatly reduced as compared with the frequency offset one symbol before is determined to include an error and is not used for the averaging process. Detection accuracy can be improved.

[0035] The base station apparatus according to the ninth aspect of the present invention comprises:
OFDM according to any of the first to eighth aspects
A configuration including a receiving device is employed.

According to this configuration, it is possible to increase the signal transmission speed in transmission / reception of the OFDM system.

[0037] A communication terminal apparatus according to a tenth aspect of the present invention is the communication terminal apparatus according to any one of the first to ninth aspects.
A configuration including a DM receiver is adopted.

According to this configuration, it is possible to increase the signal transmission speed in transmission and reception in the OFDM system.

An OFDM receiving method according to an eleventh aspect of the present invention includes a difference detecting step of detecting a difference between an absolute value of an in-phase component and an absolute value of a quadrature component of a quadrature-modulated OFDM reception signal; A quadrant determining step of determining a quadrant to which the phase of the received signal belongs in the orthogonal plane based on an output of the detecting means; and a phase detection for detecting a phase of the received signal from an output of the difference detecting step and an output of the quadrant determining step. A frequency offset detecting step of detecting a frequency offset by performing a subtraction process on the detected phase and the phase obtained by delaying the detected phase by a predetermined symbol, and detecting the received signal using the detected frequency offset. And a frequency offset compensation step of performing frequency offset compensation.

According to this method, when the frequency offset of the received signal is detected, the detection is performed by subtracting the absolute value of the I component and the absolute value of the Q component of the received signal and determining the quadrant to which the phase belongs. That is, since only the subtraction process is used and the multiplication process is not used, the amount of calculation required for frequency offset detection can be reduced, the processing speed can be increased, and as a result, the signal transmission speed of the OFDM receiver can be increased.

[0041] In the OFDM receiving method according to a twelfth aspect of the present invention, in the eleventh aspect, the frequency offset detecting step includes an averaging step of averaging the calculated frequency offset.

According to this method, since the phase error can be removed from the frequency offset to be detected, the detection accuracy of the frequency offset can be improved.

In the OFDM reception method according to a thirteenth aspect of the present invention, in the twelfth aspect, in the averaging step, only the phase of a received signal having a reception level larger than an arbitrary constant value is averaged. I made it.

According to this method, the frequency offset when the reception level of the received signal is lower than the threshold value is determined to include an error, and is not included in the averaging process.
The detection accuracy of the frequency offset can be improved.

[0045] In the OFDM reception method according to a fourteenth aspect of the present invention, in the twelfth aspect or the thirteenth aspect, the averaging step may include the step of: Only the averaging process was performed.

According to this method, a frequency offset lower than the threshold value is determined to include an error and is not included in the averaging process, so that the frequency offset detection accuracy can be improved.

According to a fifteenth aspect of the present invention, in the OFDM reception method according to any one of the eleventh to fourteenth aspects, the phase detection step may include the step of: The number of sampling of the in-phase component and the quadrature component is reduced.

According to this method, the signal processing can be sped up in order to reduce the sampling frequency.

[0049] The OFDM receiving method according to a sixteenth aspect of the present invention provides the OFDM receiving method according to the twelfth aspect, wherein a serial-parallel conversion step of converting the in-phase component and the quadrature component of the received signal into a plurality of series signals, respectively, A phase detection step;
And a phase detection step for orthogonal components.

According to this method, the frequency offset can be detected by parallel processing, so that the signal processing speed can be increased.

[0051] In the OFDM reception method according to a seventeenth aspect of the present invention, in the twelfth aspect, the phase detection step is:
The channel of the received signal is identified, and only the signal of the specific channel is taken in.

According to this method, since only the signal of a specific channel is used for phase detection, the amount of signals to be processed is reduced.
The processing speed can be increased, and the power consumption can be reduced.

In the OFDM receiving method according to an eighteenth aspect of the present invention, in any one of the twelfth aspect to the seventeenth aspect, the averaging step may include the step of: , And when the result of the subtraction exceeds an arbitrary fixed value, the current frequency offset value is not used in the averaging process.

According to this method, the frequency offset whose value is greatly reduced as compared with the frequency offset one symbol before is determined to include an error, and is not used for the averaging process. Detection accuracy can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 1 of the present invention.

First, referring to FIG.
The configuration of the FDM receiver will be described. Quadrature detector 1
01 is controlled by a local signal output from an oscillator 112 described later, and performs quadrature detection processing on an input received signal. The LPFs 102 and 103 remove unnecessary frequency components. The A / D converters 104 and 105 convert the input analog signal into a digital signal.

FFT circuit 106 applies F
The FT process is performed, and the delay detector 107 performs the delay detection process on the input signal. The determiner 108 determines a differential detection signal.

The phase information generator 109 generates phase information of the input signal. The configuration of the phase information generator 109 will be described later in detail. The subtractor 110 performs a subtraction process on the two input signals, and the delay unit 111 delays the input signal by one symbol. The oscillator 112 is connected to the subtractor 11
A local signal corrected by the phase difference which is the output of 0 is output.

Next, the operation of the OFDM receiving apparatus according to the present embodiment will be described. First, the operation related to demodulation will be described. The quadrature detector 101 performs quadrature detection processing on a received signal to obtain a baseband signal that is an analog signal. This baseband signal is
Unnecessary frequency components are removed by 2 and 103, and A / D
The digital signals are converted by the converters 104 and 105 into digital baseband signals.

The digital baseband signal is subjected to FFT processing by the FFT circuit 106 to obtain a signal assigned to each subcarrier. Further, the delay detector 1
07, a delay detection process is performed, a determination is made by the determiner 108, and a demodulated signal is obtained.

Next, operations related to frequency offset detection and frequency offset compensation will be described. The phase information generator 109 generates phase information of the received signal from an in-phase component (hereinafter, referred to as an I component) and a quadrature component (hereinafter, referred to as a Q component) of the received signal before the FFT processing.

The subtractor 110 subtracts the phase information output from the phase information generator 109 and the phase information delayed by one symbol by the delay unit 111 to calculate a phase rotation, that is, a frequency offset. The oscillator 112
The local signal corrected using the frequency offset output from the subtractor 110 is output to the quadrature detector 101. Thus, frequency offset compensation is performed.

Here, the phase information generator according to the present embodiment will be described with reference to FIG. FIG. 2 is a main part block diagram showing a schematic configuration of the phase information generator of the OFDM receiving apparatus according to Embodiment 1 of the present invention. The phase information generator according to the present embodiment does not include a multiplier, and reduces the amount of calculation for obtaining a frequency offset.

The I and Q components of the input signal are subjected to absolute value detection by absolute value detectors 201 and 202, respectively, and output to a subtractor 203.

The I and Q components of the input signal are input to the quadrant determiner 204, where the quadrant is determined. Hereinafter, the quadrant determiner 204 will be described in detail.

The phase is obtained from the I component and the Q component of the input signal.
The phase of the input signal Θ = arctan (Q / I)
It is necessary to calculate, this arctan (Q / I)
Is I ^Two+ Q^TwoAssuming = 1, approximate by
be able to. arctan (Q / I) = | I |-| Q |-

FIG. 3 shows arctan (Q / I) and | I |
6 is a graph showing a relationship with − | Q |. Like this
= | I |-| Q |, the error can be kept within 1.8 °.

Based on the above approximation, the quadrant determiner 204 determines that the quadrant is the first quadrant if | I | − | Q | {−4} / π + 1. Similarly, | I | − | Q ｜ {4} /
If π-3, the second quadrant, | I |-| Q | {-4} / π
If -3, the third quadrant, | I |-| Q | {4} / π + 1
If so, it is determined to be the fourth quadrant.

Next, the converter 205 converts the output of the subtractor 203 according to the judgment result of the quadrant judging unit 204 to obtain the phase Θ.

As described above, according to the present embodiment, when detecting the frequency offset of the received signal, the multiplication processing is not used, and the absolute value of the I component and the absolute value of the Q component of the received signal are subtracted. Since the detection is performed by determining the quadrant to which the phase belongs, the amount of calculation required for frequency offset detection can be reduced, the processing speed can be increased, and as a result, the signal transmission speed of the OFDM receiver can be increased.

(Embodiment 2) The OFDM receiving apparatus according to Embodiment 2 of the present invention is the OFDM receiving apparatus according to Embodiment 1.
It has the same configuration as that of the receiving apparatus, but normalizes the phase information based on the envelope information, thereby increasing the signal transmission speed even when the received signal is not normalized.

The OFDM receiver according to the present embodiment will be described below with reference to FIGS. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description is omitted.

FIG. 4 shows an OF according to the second embodiment of the present invention.
FIG. 3 is a main block diagram illustrating a schematic configuration of a phase information generator of the DM receiving device. The I and Q components of the input signal are input to an envelope generator 401, and envelope information is calculated. Next, the normalization circuit 402 normalizes the input signal using the calculated envelope information. The converter 205 converts the normalized input signal according to the determination result of the quadrant determiner 204 to obtain phase information.

Hereinafter, the configurations and operations of the envelope generator 401 and the normalization circuit 402 will be described in detail.

The envelope information Z is expressed as follows: Z = √ (| I | ² + | Q
| ² ), but obtaining a sum of squares requires a relatively large amount of calculation. Therefore, it is conceivable to perform an approximate calculation with Z = | I | + | Q | so that only a small amount of calculation is required.
°), an error of 1.414 times the value calculated by the sum of squares √ (| I | ² + | Q | ² ), that is, about 41% occurs, and the error rate characteristic deteriorates.

Therefore, in this embodiment, an approximate expression using multiplication that can be easily performed by bit shifting is used. That is, when | I |> | Q |, Z = | I | +
0.375 × | Q |, when | Q |> | I |, Z = | Q
| + 0.375 × | I | is used as an approximate expression.

FIG. 5 shows that | I |> | Q
FIG. 6 is a graph showing the results obtained by theoretical calculation of the relationship between the phase θ and the estimated radius, that is, the amplitude, in the case of |, that is, in the range of 0 ≦ θ ≦ 45 °. From this graph, it can be seen that the use of the above-described approximate expression enables envelope information to be obtained with an error of 7% or less as compared with the case where the square sum is obtained.

Hereinafter, the envelope generator 401 for obtaining the envelope information by using the above approximate expression will be described with reference to FIG. FIG. 6 is a main block diagram showing a schematic configuration of the envelope generator according to Embodiment 2 of the present invention.

The I and Q components of the input signal are input to absolute value detectors 601 and 602. Absolute value detector 601,
602 takes the absolute value of the input signal and outputs it to the subtractor 605 and the adder 610. Selection of the I component and the Q component is performed by switches 603 and 604. The result of the subtraction by the subtractor 605 is determined by the determiner 606, and the result of the determination is reflected in the control of the switches 603 and 604.

The 2-bit shifter 607 and 3-bit shifter 608 shift the output of the switch 604 by 2 bits and 3 bits, respectively. The outputs of the 2-bit shifter 607 and the 3-bit shifter 608 are added by an adder 609. Thereby, 0.3 in the above approximate expression is obtained.
A multiplication process of 75 is performed. The adder 610 adds the output of the switch 603 and the output of the adder 609, and outputs envelope information.

Next, the operation of the envelope generator of the phase information generator according to the present embodiment will be described.

The absolute values of the I and Q components are detected by absolute value detectors 601 and 602, respectively.
Q | is obtained.

Next, the outputs (| I | and | Q |) of the absolute value detectors 601 and 602 are subjected to a subtraction process in a subtractor 605, and the output from the subtractor 605 determines the magnitude.
The outputs of the absolute value detectors 601 and 602 (| I | and | Q
|) Is selected and output by switches 603 and 604, respectively. The switches 603 and 604 are connected to the decision unit 6
A signal to be output is selected according to the result of the determination in step 06.

The switch 603 outputs | I | if the output of the decision unit 606 is | I |> | Q |, and | Q |> | I
If |, | Q | is output. The switch 604 outputs | Q | when the output of the decision unit 606 is | I |> | Q |, and outputs | I | when | Q |> | I |. That is, the switch 603 outputs the larger of | I | and | Q |, and the switch 604 outputs the smaller of | I | and | Q |.

Next, the signal output from switch 604 |
The smaller of I | and | Q | is shifted by 2 bits and 3 bits by 2-bit shifter 607 and 3-bit shifter 608, respectively.

Since the amplitude is halved by the 1-bit shift, the amplitude is 0.25 times by the 2-bit shift and 0.125 times by the 3-bit shift. Therefore, the 2-bit shifter 6
The amplitude of the output signal of 07 is 0.25 times the amplitude of the output signal of the switch 604, and the amplitude of the output signal of the 3-bit shifter 608 is 0.125 times the amplitude of the output signal of the switch 604.

Next, the adder 609 outputs the output signal of the 2-bit shifter 607 (0.25 × | I | or 0.25 × |
Q |) and the output signal of the 3-bit shifter 608 (0.12
5 × | I | or 0.125 × | Q |)
The output signal of the adder 609 is 0.375 × | I | or 0.375 × | Q |.

Finally, the adder 610 sets the switch 603
Output signal (| I | or | Q |) and the output signal of the adder 609 (0.375 × | I | or 0.375 × | Q |).
Are added to obtain envelope information Z based on the approximate expression.

As described above, the envelope information generator according to the present embodiment does not perform the sum-of-squares calculation in the calculation of the envelope, and can perform simple multiplication and addition that can be realized by a bit shift on a circuit. Since an approximation formula consisting only of the above is used, a multiplier is not required, and the necessary amount of calculation can be reduced.
Processing speed is improved.

Next, a normalization circuit included in the phase information generator according to the present embodiment will be described with reference to FIG. FIG. 7 is a main block diagram showing a schematic configuration of a normalization circuit of the phase information generator according to Embodiment 2 of the present invention.

The determiners 701 to 704 determine whether the phase is larger or smaller than π / 4.
05 to 707 add the bit-shifted input signal and the envelope signal of which polarity is inverted or not in accordance with the result of the decision unit one symbol before.

By adopting such a configuration, it is possible to remove the information of the envelope from the input signal. Then, the output of the decision unit 701 indicates that the phase of the input signal is π in the quadrant.
The output of the determiner 702 is determined whether the output of the determiner 702 is greater than or less than π / 8 within the range of π / 4 determined by the determiner 701, and the output of the determiner 703 is determined by the determiner 702. The output of the decision unit 704 indicates whether it is π / 16 or more within the range of π / 8 determined and the output of the decision unit 704 is π / 32 or more within the range of π / 16 determined by the decision unit 703.

Here, the case where the output normalized signal is composed of 4 bits has been described. However, an arbitrary number of determiners and arithmetic units can be provided, and the greater the number, the higher the accuracy.
Also, as is clear from FIG. 7, the number of arithmetic units must be equal to the number of decision units minus one.

As described above, the normalization circuit of the phase information generator according to the present embodiment does not require a multiplier, can reduce the required amount of calculation, and improves the processing speed.

As described above, according to the present embodiment, the amount of calculation required for frequency offset detection is reduced by performing the phase information generation and the accompanying envelope generation and normalization processing without using a multiplier. Then, the processing speed can be increased, and as a result, the signal transmission speed of the OFDM receiver can be increased. Further, since the present invention can be applied even when the received signal is not normalized, it is possible to cope with more communication modes than in the first embodiment.

(Embodiment 3) The OFDM receiving apparatus according to Embodiment 3 of the present invention provides the OFDM receiving apparatus according to Embodiment 1.
It has the same configuration as the receiving device, except that the calculated phase information is averaged and then used for correction.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 8 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 3 of the present invention. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The averaging device 801 performs an averaging process on the frequency offset output from the subtractor 110. By this processing, the phase error due to thermal noise or the like can be reduced, and the detection accuracy of the frequency offset can be increased.

As described above, according to the present embodiment, the amount of calculation required for frequency offset detection is reduced by performing phase information generation and the accompanying envelope generation and normalization processing without using a multiplier. Then, the processing speed can be increased, and as a result, the signal transmission speed of the OFDM receiver can be increased. Also, in order to reduce the phase error by the averaging process,
The accuracy of detecting the frequency offset can be increased as compared with the first embodiment.

(Embodiment 4) The OFDM receiving apparatus according to Embodiment 4 of the present invention provides the OFDM receiving apparatus according to Embodiment 3.
It has the same configuration as that of the receiving apparatus, except that the phase information whose signal level is below the threshold is not used for the averaging process.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 9 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 4 of the present invention. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

A signal having a low signal level has a low signal-to-noise power ratio, so that a phase error due to thermal noise or the like becomes large.
In view of this point, in the present embodiment, a signal having a low signal level is not used for the averaging process.

The subtractor 901 performs a subtraction process between the output of the phase information generator 109 and the threshold value, and the determiner 902 determines the magnitude. This determination result controls the switch 903,
Only when the signal level of the phase information is equal to or higher than the threshold value, the output of the subtractor 110 is input to the averager 801.

As described above, according to the present embodiment, the signal whose signal level is lower than the threshold is not used for the averaging process, so that the detection accuracy of the frequency offset can be further improved as compared with the third embodiment. Can be.

(Embodiment 5) The OFDM receiving apparatus according to Embodiment 5 of the present invention provides the OFDM receiving apparatus according to Embodiment 3.
It has the same configuration as the receiving device, except that the frequency offset below the threshold is not used for the averaging process.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 10 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 5 of the present invention. In the figure, the fourth embodiment
The same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

If it is determined that the frequency offset calculated from the phase information is excessive, it is considered that the phase information contains an error. Therefore, the frequency offset exceeding the threshold value is used for the averaging process. Not to be.

The subtractor 1001 performs a subtraction process on the frequency offset and the threshold value, which are the outputs of the subtractor 110, and the determiner 1002 makes a magnitude determination. The result of this determination is
03 is controlled so that the output of the subtractor 110 is input to the averager 801 only when the frequency offset is equal to or less than the threshold value.

As described above, according to the present embodiment, the frequency offset below the threshold is not used for the averaging process, so that the accuracy of detecting the frequency offset can be further improved as compared with the fourth embodiment. .

(Embodiment 6) The OFDM receiving apparatus according to Embodiment 6 of the present invention provides the OFDM receiving apparatus according to Embodiment 5.
It has the same configuration as that of the receiving apparatus, except that the threshold used is changed according to the line quality.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 11 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 6 of the present invention. In FIG.
The same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

When the signal-to-noise power ratio is low, the influence of thermal noise and the like becomes large, and the amplitude error and the phase error become large. Therefore, the channel quality is estimated using the demodulation signal determination error, and the channel quality is estimated. Try changing the threshold.

The subtractor 1101 performs a subtraction process on the input signal and the output signal of the determiner 108, and the determiner 1102 determines the magnitude. The result of this decision unit is a decision error of the demodulated signal. The switch 1103 is controlled by a determination error output from the determiner 1102, and selectively outputs a threshold A and a threshold B. Here, the threshold value A is larger than the threshold value B. If the determination error exceeds a certain value, the larger threshold value A is output to the subtractor 1001; Is output as the threshold value B.

As described above, according to the present embodiment, by making the threshold variable according to the channel quality, it is possible to improve the frequency offset detection accuracy as compared with the fifth embodiment.

(Embodiment 7) The OFDM receiving apparatus according to Embodiment 7 of the present invention provides the OFDM receiving apparatus according to Embodiment 3.
It has the same configuration as the receiving device, except that the received signal after A / D conversion is input to the phase information generator after passing through the LPF.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 12 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 7 of the present invention. Note that, in FIG.
The same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

The LPFs 1201 and 1202 remove unnecessary frequency components from the output signals of the A / D converters 104 and 105 and output the signals to the phase information generator 109.

In particular, when the cutoff frequency of the LPF is lowered, the effect of removing unnecessary frequency components increases, and the signal-to-noise power ratio can be improved. The frequency offset is
In order to detect using the signal before FFT which is a multiplex signal,
Even if the cutoff frequency of the LPF is lowered, the detection accuracy of the frequency offset does not decrease.

As described above, according to the present embodiment, after removing unnecessary frequency components from the received signal by the LPF,
Since the signal is input to the phase information generator, the detection accuracy of the frequency offset can be further improved as compared with the third embodiment.

(Embodiment 8) The OFDM receiving apparatus according to Embodiment 8 of the present invention provides the OFDM receiving apparatus according to Embodiment 7.
It has the same configuration as the receiving device, except that the sampling frequency is reduced to increase the signal transmission speed.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 13 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 8 of the present invention. In FIG.
The same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

The decimating circuits 1301 and 1302 are provided with LPFs.
The sampling frequency is reduced by thinning out the received signals after passing through 1201 and 1202. Since the noise bandwidth of the signal after passing through the LPF is reduced, the sampling frequency can be reduced.

As described above, according to the present embodiment, it is possible to increase the signal transmission speed by reducing the sampling frequency.

(Embodiment 9) The OFDM receiving apparatus according to Embodiment 9 of the present invention provides the OFDM receiving apparatus according to Embodiment 7.
It has the same configuration as the receiving device, except that it is input to the phase information generator after passing through an analog LPF.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described using FIG. FIG. 14 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 9 of the present invention. In FIG.
The same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

LPFs 1401 and 1402 are analog filters and remove unnecessary frequency components. LPF14
01 and 1402 are output from A / D converters 1403 and 14
04, and is converted into a digital signal.
9 is input.

As described above, according to the present embodiment, the operation of the A / D converter is further improved as compared with the eighth embodiment by using an analog filter for the LPF that passes the signal before being input to the phase information generator. Speed can be reduced,
Signal transmission speed can be increased.

(Embodiment 10) Embodiment 1 of the present invention
0 according to the third embodiment.
It has the same configuration as the DM receiver, except that it performs averaging processing on a plurality of symbols.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 15 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 10 of the present invention. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The delay unit 1501 delays the output of the averaging unit 801. Then, the averaging unit 1502 averages the output of the averaging unit 801 and the output of the delay unit 1501.

As described above, according to the present embodiment, the averaging process is performed on a plurality of symbols.
It is possible to further improve the detection accuracy of the frequency offset.

(Embodiment 11) Embodiment 1 of the present invention
1 according to the third embodiment.
It has the same configuration as the DM receiver, except that the calculation of the frequency offset is performed by parallel processing to improve the processing speed.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described using FIG. FIG. 16 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 11 of the present invention. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

Serial-Parallel converters (hereinafter, referred to as S / P converters) 1601 and 1602 are:
The output of each of the A / D converters 104 and 105 is converted into a plurality of signals.

Hereinafter, the calculation of the frequency offset is performed in parallel. That is, phase information generators 1603 and 1604
Calculates the phase information respectively, and subtracters 1605 and 16
06 performs a subtraction process on the phase information and the phase information delayed by the delay units 1607 and 1608 to detect a frequency offset.

As described above, Embodiment 11 of the present invention provides
Since the frequency offset detection is performed by parallel processing, the signal transmission speed can be increased.

(Embodiment 12) Embodiment 1 of the present invention
The OFDM receiver according to Embodiment 2 is the OFDM receiver according to Embodiment 3.
It has the same configuration as the DM receiver, except that frequency offset detection is performed using only a specific channel.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG. 17 is a main block diagram showing a schematic configuration of the OFDM receiving apparatus according to Embodiment 12 of the present invention. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

Switches 1701 and 1702 allow only a specific channel, for example, a control channel, to be input to phase information generator 109 based on the channel type signal. Since the frequency offset value does not change abruptly with the passage of time, there is no effect even if frequency offset detection is performed only on a specific channel.

As described above, according to the present embodiment, frequency offset detection is performed using only a specific channel, so that the average power consumption can be reduced.

(Embodiment 13) Embodiment 1 of the present invention
3 according to the tenth embodiment.
It has a configuration similar to that of the FDM receiver, except that the average value of the frequency offset in the averaging device is a weighted average of the calculated frequency offset, the frequency offset value one symbol before, and the weighted average.

Hereinafter, the averaging unit of the OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG.
FIG. 8 is a principal block diagram showing a schematic configuration of an averaging device of an OFDM receiving apparatus according to Embodiment 13 of the present invention.

If the number of symbols to be averaged is increased, the accuracy of frequency offset detection is improved, but the required memory capacity is increased. Therefore, in the present embodiment, the frequency offset averaging process is performed using the following equation. aveΔf (n) = (l−α) × aveΔf (n−1) + α × Δf (n) − where Δf (n) represents the frequency offset value at the current time, and similarly, aveΔf (n) is Α represents the average value of the frequency offset at the current time, and α represents a coefficient (for example, 0.1) used for the weighted averaging process. n is 0,
Take 1, 2, ....

The configuration and operation of an averaging device for realizing the above equation will be described. The multiplier 1801 multiplies the frequency offset at the current time by 0.1. This corresponds to α × Δf (n) in the equation. The memory 1802 is a memory for storing a frequency offset after averaging one symbol before. The frequency offset one symbol before is calculated by the multiplier 1
803 is multiplied by 0.9. This corresponds to (l−α) × aveΔf (n−1) in the equation. An adder 1804 adds the outputs of the multipliers 1801 and 1803 and outputs the result as a frequency offset after the averaging process.

As described above, when performing the weighted averaging with the calculated frequency offset and the frequency offset value one symbol before, the memory only needs to store the average value of the previous frequency offset. The frequency offset detection accuracy can be improved without increasing.

Therefore, according to the present embodiment, when averaging processing is performed on a plurality of symbols, the accuracy of frequency offset detection can be improved without increasing the memory capacity.

(Embodiment 14) Embodiment 1 of the present invention
4 according to the eleventh embodiment.
It has the same configuration as the FDM receiver, except that the coefficients used for weighted averaging are variable.

Hereinafter, the averaging device of the OFDM receiving apparatus according to the present embodiment will be described with reference to FIG. FIG.
FIG. 9 is a main block diagram showing a schematic configuration of an averaging device of an OFDM receiving apparatus according to Embodiment 14 of the present invention. In the drawing, the same components as those of the thirteenth embodiment are denoted by the same reference numerals, and the detailed description is omitted.

The smaller the value of the coefficient α used in the weighted averaging process, the higher the frequency offset detection accuracy, but the slower the convergence speed. The convergence speed increases as the value increases, but the detection accuracy deteriorates. Therefore, in the present embodiment,
The value of α is, for example, a large value (for example, 0.5) for the first four symbols, and a small value (for example, 0.1) thereafter.
By doing so, both detection accuracy and convergence speed are achieved.

The switch 1901 outputs, for example, 0.5 to the first four symbols and 0.1 to the fifth and subsequent symbols to the multiplier 1801. Similarly, switch 19
02 is output to the multiplier 1801, for example, 0.5 for the first four symbols and 0.9 for the fifth and subsequent symbols.

As described above, the fourteenth embodiment of the present invention
By making the coefficient used for weighted averaging variable, it is possible to achieve both higher accuracy and faster convergence than in the thirteenth embodiment.

(Embodiment 15) Embodiment 1 of the present invention
The OFDM receiver according to the fifth embodiment is the OFDM receiver according to the thirteenth embodiment.
It has the same configuration as that of the FDM receiver, except that the coefficient used for the weighted average is a value that can be realized by the bit shift and the adder / subtractor.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described using FIG. FIG. 20 is a main block diagram showing a schematic configuration of an averaging device of the OFDM receiving apparatus according to Embodiment 15 of the present invention. In the figure,
The same components as those in the thirteenth embodiment are denoted by the same reference numerals, and detailed description is omitted.

As described in the second embodiment, the amplitude can be halved by performing the 1-bit shift, so that the 2-bit shift achieves 0.25 times and the 3-bit shift achieves 0.125 times. be able to. Therefore, the value of the coefficient α used in the weighted averaging process in the equation is set to a value (for example, 0.2
By adopting 5), the multiplier can be omitted from the averaging device.

The two-bit shifter 2001 shifts the frequency offset at the current time by two bits to make it 0.25 times. 2 bit shifter 2002 and 1 bit shifter 2
003 shifts the frequency offset one symbol before, which is the output of the memory 1802, by 2 bits and 1 bit, respectively, to be 0.25 times and 0.5 times, respectively.

The adder 2004 includes a 2-bit shifter 20
02 and the output of the 1-bit shifter 2003, and
Generate 0.75 times the frequency offset before the symbol. Finally, the adder 1804 includes the 2-bit shifter 200
1 is added to the output of the adder 2004, and α = 0.
The equation for the case of 25 can be realized on a circuit.

As described above, according to the present embodiment, when weighted averaging is used in the averaging unit, weighted averaging can be performed only by bit shift and adder / subtractor without using a multiplier. The circuit scale can be reduced as compared with Embodiments 13 and 14.

(Embodiment 16) Embodiment 1 of the present invention
6 according to the OFDM reception apparatus according to the third embodiment.
It has the same configuration as the DM receiver, except that if the difference between the current time frequency offset value and the average value of the previous frequency offset exceeds a threshold value, the current time frequency offset value is used for averaging processing. Not used.

Hereinafter, an OFDM receiving apparatus according to the present embodiment will be described using FIG. 21 and FIG. FIG.
FIG. 1 is a main block diagram showing a schematic configuration of an OFDM receiver according to Embodiment 16 of the present invention. FIG. 22 is a schematic configuration of a control circuit of the OFDM receiver according to Embodiment 16 of the present invention. It is a principal part block diagram shown. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

When the signal-to-noise power ratio is low, the frequency offset value detected for each symbol varies, and in this embodiment, the difference from the frequency offset value one symbol before exceeds a certain value. The frequency offset value includes an error and is not used in the averaging process.

In FIG. 21, the control circuit 2101 includes:
An averaged frequency offset value output from the averaging unit 801 and a frequency offset value one symbol before output from the averaging unit 2102 are input. Control circuit 21
The output of 01 controls the switch 2103, and inputs the output of the averager 801 to the averager 2102 only when the difference from the frequency offset one symbol before is equal to or smaller than the threshold.

On the other hand, in FIG.
Then, the subtractor 2201 performs a subtraction process between the current-time frequency offset output from the averaging device 801 and the frequency offset one symbol before output from the averaging device 2102. Next, the subtractor 2202 performs a subtraction process between the output of the subtractor 2201 and the threshold value, and the determiner 2203 makes a magnitude determination. The result of the magnitude determination controls the switch 2103 as a control signal.

As described above, according to the present embodiment, when the difference between the frequency offset value at the current time and the frequency offset value one symbol before exceeds the threshold value, the frequency offset value at the current time is averaged. By not using it for
Accuracy of frequency offset detection can be improved.

(Embodiment 17) Embodiment 1 of the present invention
7 according to the OFDM receiver of the sixteenth embodiment.
It has a configuration similar to that of the FDM receiver, except that the threshold value in the control circuit is changed according to the line quality.

Hereinafter, the OFDM receiving apparatus according to the present embodiment will be described using FIG. 23 and FIG. FIG.
FIG. 3 is a main block diagram showing a schematic configuration of an OFDM receiver according to Embodiment 17 of the present invention. FIG. 24 is a schematic configuration of a control circuit of the OFDM receiver according to Embodiment 17 of the present invention. It is a principal part block diagram shown. In the figure, the same components as those of the third embodiment are denoted by the same reference numerals, and the detailed description is omitted.

If the threshold value in the control circuit described in the sixteenth embodiment is constant, it causes a decrease in frequency offset detection accuracy in a situation where the line quality is poor, and the convergence speed is reduced in a situation where the line quality is good. It is desirable to vary the threshold value according to the line quality state, because it causes a delay. In the present embodiment, for example, a large and small binary threshold value is provided and selectively used according to the line quality. Here, as the channel quality, a determination error of a demodulated signal is used as in the sixth embodiment.

In FIG. 23, a subtractor 2301 performs a subtraction process on the input signal and the output signal of the decision unit 108, and
302 determines the magnitude. The result of this decision unit is a decision error of the demodulated signal. This determination error is input to the control circuit 2101.

In FIG. 24, a switch 2401 is controlled by the line quality information output from the decision unit 2302, and selectively outputs a threshold A or a threshold B. Here, if threshold value A> threshold value B, threshold value A, which is the larger value, is subtracted when the line quality is poor.
2 and, if the line quality is good, the smaller threshold value B is output to the subtractor 2202.

As described above, according to the present embodiment, the threshold used in the control circuit is changed according to the line quality, thereby achieving both higher frequency offset detection accuracy and convergence speed than in the sixteenth embodiment. Can be.

In any of the above embodiments, the phase difference is converted by the quadrant to which the phase belongs based on the absolute value of the in-phase component and the absolute value of the quadrature component of the received signal, and the phase information of the received signal is easily calculated. A frequency offset is calculated by subtracting the phase information of the received signal and the phase information of one symbol before, and the frequency offset is compensated by using the calculated frequency offset.
Since it is possible to omit the multiplier having a low processing speed, the processing speed of the OFDM receiver can be increased.
Signal transmission speed can be increased.

[0172]

As described above, according to the present invention,
The processing speed of the frequency offset detection circuit can be improved, and the signal transmission speed can be improved.

[Brief description of the drawings]

FIG. 1 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a main block diagram showing a schematic configuration of a phase information generator of the OFDM receiving apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a graph showing a theoretical calculation result of a phase calculation approximate expression used in the phase information generator according to the first embodiment of the present invention.

FIG. 4 is a main block diagram showing a schematic configuration of a phase information generator of the OFDM receiving apparatus according to Embodiment 2 of the present invention.

FIG. 5 is a graph showing theoretical calculation results of an approximate expression for calculating envelope information used in the phase information generator according to Embodiment 2 of the present invention;

FIG. 6 is a main block diagram showing a schematic configuration of an envelope generator according to Embodiment 2 of the present invention;

FIG. 7 is a main block diagram showing a schematic configuration of a normalization circuit of the phase information generator according to Embodiment 2 of the present invention;

FIG. 8 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 3 of the present invention.

FIG. 9 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 4 of the present invention.

FIG. 10 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 5 of the present invention.

FIG. 11 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 6 of the present invention.

FIG. 12 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 7 of the present invention.

FIG. 13 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 8 of the present invention.

FIG. 14 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 9 of the present invention.

FIG. 15 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 10 of the present invention.

FIG. 16 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 11 of the present invention.

FIG. 17 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 12 of the present invention.

FIG. 18 is a main block diagram showing a schematic configuration of an averaging device of an OFDM receiving apparatus according to Embodiment 13 of the present invention.

FIG. 19 is a main block diagram showing a schematic configuration of an averaging device of an OFDM receiving apparatus according to Embodiment 14 of the present invention.

FIG. 20 is a main block diagram showing a schematic configuration of an averaging device of an OFDM receiving apparatus according to Embodiment 15 of the present invention.

FIG. 21 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 16 of the present invention.

FIG. 22 is a main block diagram showing a schematic configuration of a control circuit of an OFDM receiver according to Embodiment 16 of the present invention.

FIG. 23 is a main block diagram showing a schematic configuration of an OFDM receiving apparatus according to Embodiment 17 of the present invention.

FIG. 24 is a main block diagram showing a schematic configuration of a control circuit of the OFDM receiver according to Embodiment 17 of the present invention.

FIG. 25 is a main block diagram showing a schematic configuration of a conventional OFDM receiver.

FIG. 26 is a schematic view of a frame format in OFDM wireless communication;

[Explanation of symbols]

 Reference Signs List 101 Quadrature detector 106 FFT circuit 107 Delay detector 108 Judge 109 Phase information generator 112 Oscillator 201, 202 Absolute value detector 204 Quadrant judge 205 Transformer 401 Envelope generator 402 Normalization circuit 607 2-bit shifter 608 3-bit shifter 801 Averaging unit 1201, 1202 LPF 1301, 1302 Thinning circuit 1601, 1602 S / P converter 2101 Control circuit

Continuation of the front page (72) Inventor Mitsuru Uesugi 3-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture F-term in Matsushita Communication Industrial Co., Ltd. 5K022 DD13 DD19 DD33 DD43

Claims (18)

[Claims] 1. A difference detection means for detecting a difference between an absolute value of an in-phase component and an absolute value of a quadrature component of a quadrature-modulated OFDM reception signal, and a reception signal in an orthogonal plane based on an output of the difference detection means. A quadrant determining means for determining a quadrant to which a phase belongs; a phase detecting means for detecting a phase of the received signal from an output of the difference detecting means and an output of the quadrant determining means; and a detected phase and a detected phase. Frequency offset detection means for detecting the frequency offset by subtracting the phase delayed by a predetermined symbol, and frequency offset compensation means for performing frequency offset compensation on the received signal using the detected frequency offset,
An OFDM receiving apparatus comprising: 2. The OFDM receiving apparatus according to claim 1, wherein said frequency offset detecting means has an averaging section for averaging the calculated frequency offset. 3. The OFDM receiving apparatus according to claim 2, wherein the averaging section averages only a phase of a received signal having a received level higher than an arbitrary fixed value. 4. The OFDM receiving apparatus according to claim 2, wherein the averaging unit averages only a frequency offset exceeding an arbitrary fixed value from the calculated frequency offsets. . 5. The phase detection unit according to claim 1, wherein the phase detection unit includes a thinning unit that reduces the number of samplings of the in-phase component and the quadrature component of the received signal after removing unnecessary frequency components. 5. The OFDM receiver according to claim 1. 6. A serial-to-parallel converter for converting an in-phase component and a quadrature component of a received signal into a plurality of series signals, a phase detector for the in-phase component, and a phase detector for the quadrature component. The O according to claim 2, wherein
FDM receiver. 7. The OFDM receiver according to claim 2, wherein said phase detecting means identifies a channel of a received signal and takes in only a signal of a specific channel. 8. The averaging unit subtracts the current frequency offset value from the frequency offset value one symbol before, and when the result of the subtraction exceeds an arbitrary fixed value, the averaging unit performs the subtraction processing. 8. The OFDM receiver according to claim 2, wherein the value is not used for the averaging process. 9. A base station apparatus comprising the OFDM receiving apparatus according to claim 1. 10. A communication terminal device comprising the OFDM receiver according to claim 1. Description: 11. A difference detection step for detecting a difference between an absolute value of an in-phase component and an absolute value of a quadrature component of a quadrature-modulated OFDM reception signal, and a reception signal in an orthogonal plane based on an output of the difference detection means. A quadrant determining step of determining a quadrant to which a phase belongs; a phase detecting step of detecting a phase of the received signal from an output of the difference detecting step and an output of the quadrant determining step; a detected phase and a detected phase A frequency offset detection step of subtracting a phase delayed by a predetermined symbol to detect a frequency offset, and a frequency offset compensation step of performing frequency offset compensation on the received signal using the detected frequency offset, An OFDM receiving method, comprising: 12. The OFDM reception method according to claim 11, wherein said frequency offset detecting step includes an averaging step of averaging the calculated frequency offset. 13. The OFDM receiving method according to claim 12, wherein in the averaging step, only the phase of a received signal having a received level higher than an arbitrary fixed value is averaged. 14. The averaging process according to claim 12, wherein only the frequency offset exceeding an arbitrary fixed value from the calculated frequency offsets is averaged.
Or the OFDM reception method according to claim 13. 15. The phase detection step according to claim 11, wherein the number of samplings of the in-phase component and the quadrature component of the received signal after removing unnecessary frequency components is reduced by using a thinning circuit. 4. The OFDM receiving method according to 1. 16. A serial-parallel conversion step of converting an in-phase component and a quadrature component of a received signal into a plurality of series signals, a phase detection step for an in-phase component, and a phase detection step for a quadrature component. 13. The OFDM receiving method according to claim 12, wherein: 17. The OFDM receiving method according to claim 12, wherein in the phase detecting step, a channel of a received signal is identified and only a signal of a specific channel is taken in. 18. The averaging step subtracts the current frequency offset value and the frequency offset value one symbol before, and when the result of the subtraction exceeds an arbitrary fixed value, the average frequency offset 18. The OFDM receiving method according to claim 12, wherein the value is not used for the averaging process.