JP6821869B2 - OFDM receiver and OFDM reception method - Google Patents

Description

The present invention relates to a communication system that communicates by an Orthogonal Frequency Division Multiplexing (OFDM) method, and more particularly to a technique for estimating transmission line characteristics in a receiving device (OFDM receiving device) that receives an OFDM signal.

In recent years, in the field of wireless communication, the OFDM method has been in the limelight as a modulation method that is strong against multipath fading and mobile transmission, and many applied researches are being carried out in various countries including Europe and Japan. The OFDM method is a kind of multi-carrier modulation method, and is a transmission method in which a plurality of carriers (carriers) orthogonal to each other are digitally modulated and an information code is transmitted by these multiple carriers. The OFDM method is applied to wireless communication and broadcasting (for example, terrestrial digital television broadcasting).

In order to demodulate the signal modulated by the OFDM method, it is necessary to correct the amplitude fluctuation and the phase rotation caused in the transmission line by multipath fading or the like. In the OFDM signal system, generally, the transmitting side inserts a pilot signal into the OFDM signal at intervals of several carriers, the receiving side detects the pilot signal from the received signal, and the interception interpolation using an interpolation filter is based on the detected pilot signal. The transmission line characteristics are estimated by performing the processing, and the amplitude and phase of the received signal are corrected using the estimated transmission line characteristics.

Japanese Unexamined Patent Publication No. 2011-135204 JP-A-2002-9726

However, since the pilot signal does not exist outside the band, the signal estimation by the interpolation processing based on the pilot signal does not work well at the end of the band, and a large error may occur in the estimation result of the transmission line characteristics. For example, in the FPU (Field Pickup Unit), measures are taken such as not using the carrier in the portion where the error becomes large for data transmission.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an OFDM receiving device and an OFDM receiving method capable of accurately estimating transmission line characteristics even at the end of a band.

According to one aspect of the present invention, pilot signals are arranged on a plurality of first carriers located at predetermined carrier intervals and second carriers located at both ends of the band, and the second carrier and the second carrier are arranged. Provided is an OFDM receiver that receives an orthogonal frequency division multiplexing (OFDM) signal in which the carrier interval between the first carrier adjacent to the first carrier is smaller than the predetermined carrier interval, and the OFDM receiver is provided with the plurality of first carriers. A means for calculating the transmission line characteristics of the plurality of first carriers based on the pilot signal of one carrier, and a means for calculating the transmission line characteristics of the second carrier based on the pilot signal of the second carrier. As a means for estimating the transmission line characteristics of the second carrier by performing the frequency-direction interpolation interpolation processing using the interpolation filter based on the calculated transmission line characteristics of the plurality of first carriers. , The means for calculating the difference between the calculated transmission line characteristics of the second carrier and the estimated transmission line characteristics of the second carrier, and the adjacent second carrier based on the calculated difference. A means for estimating the transmission line characteristics of a virtual carrier located outside the band at a predetermined carrier interval from one carrier, the pilot signal of the calculated plurality of first carriers, and the estimated said. By applying the interpolation filter based on the transmission line characteristics of the virtual carrier, the means for estimating the transmission line characteristics of the carrier on which the pilot signal is not arranged is provided.

According to the present invention, the transmission line characteristics can be estimated with high accuracy.

The figure for demonstrating the basic scheme of the transmission line characteristic estimation method which concerns on embodiment of this invention. The figure for demonstrating the basic scheme of the transmission line characteristic estimation method which concerns on embodiment of this invention. The figure for demonstrating the basic scheme of the transmission line characteristic estimation method which concerns on embodiment of this invention. The block diagram which shows the structural example of the OFDM transmitter which concerns on embodiment of this invention. The figure which shows an example of the pilot arrangement which concerns on embodiment of this invention. The block diagram which shows the structural example of the OFDM receiver which concerns on embodiment of this invention. FIG. 6 is a block diagram showing a configuration example of the equalization processing unit shown in FIG. The block diagram which shows the structural example of the frequency direction interpolation part shown in FIG.

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

First, the basic scheme of the transmission line characteristic estimation method according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3.
The actual transmission signal is affected by the multipath signal during spatial propagation, and signal distortion occurs. Pilot signals, which are known signals, are inserted into the OFDM signal at regular intervals, and an insertion interpolation filter (for example, FIR (Finite Impulse Response) filter) is used on the receiving side based on the pilot signal. The transmission line characteristics are estimated by performing the interpolation processing, and the received signal is equalized based on the estimation result of the transmission line characteristics. In this way, the phase and amplitude of in-band signals other than the pilot signal are corrected.

At the time of interpolation, the transmission line characteristics are obtained from the filter response of the pilot signal. However, at the band end where the pilot signal does not continue, the response of the FIR filter is not correctly obtained, and as shown in FIG. 1, a phenomenon occurs in which the estimation result of the transmission line characteristic deviates from the original transmission line characteristic. .. In FIG. 1, the “band end” position indicates the carrier with the lowest frequency of the OFDM signal. In the example of FIG. 1, the pilot signals are arranged at intervals of 16 carriers in the frequency direction. Specifically, the pilot signals are the 17th carrier, the 33rd carrier, the 59th carrier, etc., which are the band ends. It is located in. The response of the FIR filter is shown as the "actual response". The response of the FIR filter when the OFDM signal in which the pilot signal is arranged is transmitted from the band end to the carrier (first carrier) in the low frequency band of 16 carriers is simulated, and the simulation result is shown as the "desired response". .. As shown in FIG. 1, the "actual response" to the "desired response" is in the band (18th to 32nd carriers) between the carrier at the band edge and the carrier in the high frequency range from the band edge to 16 carriers. The shift width is large, and these carriers are in a state of containing a modulation error. For this reason, it is desirable to avoid using these carriers for data transmission, but doing so results in a loss.

In FIG. 2, in addition to the above-mentioned “actual response”, the response of the equivalent FIR filter to the assumed pilot signal of the carrier (first carrier) in the low band 16 carriers from the band end is “filter response of the assumed pilot signal”. Is shown as. FIG. 2 further shows the result of adding the “filter response of the assumed pilot signal” and the “actual response”. The response obtained by adding the "filter response of the assumed pilot signal" and the "actual response" is the same as the "desired response" shown in FIG. 1, and the difference from the "actual response" is the assumed pilot. It can be seen that it is only the filter response of the signal.

In order to estimate the value corresponding to M shown in FIG. 1, the pilot signal is added at a position different from the position of the pilot signal at 16 carrier intervals. In FIG. 1, M is the difference obtained by subtracting the "actual response" from the "desired response" in the eighth carrier. In this case, a pilot signal is added to the eighth carrier. The value of the added pilot signal corresponds to the ideal response. The value of M is obtained based on the value of the added pilot signal, and the pilot signal or transmission line characteristics of a non-existing carrier (virtual carrier) outside the band are estimated based on the obtained value of M. Specifically, the virtual carrier is a carrier in the low band of 16 carriers from the band end, that is, the first carrier. The pilot signal Pg of the virtual carrier is calculated by the following formula, for example, when a 129 tap filter is used.
Pg = M / R (72) × R (65) ・ ・ ・ (1)
Here, R indicates the coefficient value of the interpolation filter. R (65) is the 65th coefficient value, and R (72) is the 72nd coefficient value. The difference from the desired response is a value that must be added as the coefficient value of the filter, and the pilot signal of the virtual carrier is estimated by correcting the value corresponding to the center coefficient from that ratio.

FIG. 3 shows the simulation results. In FIG. 3, the pilot signal added for estimating the pilot signal of the virtual carrier is shown as the “correction pilot”, and the estimation result of the pilot signal of the virtual carrier is shown as the “estimated pilot”. By estimating the pilot signal of the virtual carrier and passing it through an interpolation filter, it can be corrected to the same result as the desired response. That is, the transmission line characteristics can be estimated accurately for the carriers at the end of the band. As a result, the carriers at the band end can be equalized, and the carrier loss can be suppressed.

Although the lower end side of the band has been described above, the same applies to the upper end side of the band.

In the present embodiment, additional pilot signals for correction are required (one for each of the upper and lower ends, for a total of two), but if correction is not performed, a plurality of (for example, 30) data carriers cannot be used. Considering that, there is a big merit.

Next, the OFDM transmitter and the OFDM receiver according to the embodiment of the present invention will be described.
FIG. 4 schematically shows the OFDM transmitter 40 according to the present embodiment. As shown in FIG. 4, the OFDM transmitter 40 includes an OFDM frame generation unit 41, a correction pilot insertion unit 42, an inverse fast Fourier transformation (IFFT) unit 43, a band limiting filter 44, and a digital-to-analog converter. (DAC: Digital-to-Analog Converter) 45, a frequency converter 46, an amplifier 47, and an antenna 48 are provided.

The OFDM frame generation unit 41 receives transmission data from an external or higher-level device, and generates an OFDM frame based on the received transmission data. For example, the OFDM frame generation unit 41 performs various processes including carrier modulation such as 64QAM (Quadrature Amplitude Modulation) on the transmitted data, and further adds a pilot signal.

The OFDM frame is converted from a signal in the frequency domain to a signal in the time domain by the IFFT unit 43, and a guard interval is further added. After that, it passes through the band limiting filter 44, is converted into an analog signal by the DAC 45, is frequency-converted into a signal in the radio frequency (RF) band by the frequency conversion unit 46, is amplified by the amplifier 47, and is transmitted from the antenna 48.

FIG. 5 shows an example of the pilot arrangement according to the present embodiment. The carrier structure shown in FIG. 5 includes 913 carriers. In FIG. 5, the horizontal direction represents frequency and is also referred to as frequency direction or carrier direction, and the vertical direction represents time and is also referred to as time direction or symbol direction. Square grids arranged in the frequency direction and the time direction each represent one carrier. Therefore, a row of grids arranged in the frequency direction represents one symbol constituting the OFDM signal. The squares labeled CP indicate the position of the pilot signal. Since these pilot signals are arranged continuously in the time direction, they are called CP (Continuous Pilot). The pilot signal is, for example, BPSK (Binary Phase Shift Keying) modulated random data known to the receiver. Such pilot signals are often used in ARIBs (Associations of Radio Industries and Businesses) and the like.

In each symbol, the pilot signal is a carrier located at a predetermined carrier interval (hereinafter, also referred to as a first carrier) and a carrier located at both ends of the band (hereinafter, also referred to as a second carrier). Is located in). The portion of the carriers in the transmission band excluding the first carrier and the second carrier is referred to as a third carrier. The pilot signal of the second carrier is used to correct the transmission line characteristics, and is sometimes referred to as a correction pilot signal. The carrier interval between the second carrier and the first carrier adjacent to the second carrier is smaller than the predetermined carrier interval described above. From the viewpoint of accurately estimating the transmission line characteristics, it is desirable that the carrier spacing between the second carrier and the adjacent first carrier is at least half of the predetermined carrier spacing. In the example of FIG. 5, the predetermined carrier interval is 16 carriers, the carrier interval between the second carrier and the adjacent first carrier is 8 carriers, that is, the pilot signals are 1, 9, 25, and so on. It is located at the 41st, ..., 889, 905, and 913th carrier positions.

The correction pilot insertion unit 42 shown in FIG. 4 is shown as a functional block separate from the OFDM frame generation unit 41 in order to emphasize that the correction pilot signal is inserted into the OFDM signal, but the OFDM frame generation It can be part of part 41.

In the present embodiment, the pilot signal of the first carrier is mainly described as CP, but the pilot signal of the first carrier is not limited to CP, and SPs (SPs) distributed in the time direction and the frequency direction ( It may be Scattered Pilot). Even when the pilot signal of the first carrier is SP, the correction pilot signal is continuously arranged in the time direction. In this case, the predetermined carrier interval when the pilot signals are arranged on carriers located at predetermined carrier intervals refers to the carrier intervals between carriers in which the pilot signals are arranged at regular intervals in the time direction, and the first The first carrier adjacent to the second carrier refers to the carrier closest to the position of the second carrier among the carriers in which the pilot signals are arranged at regular intervals in the time direction. For example, when the symbol signals are arranged at intervals of 64 carriers in the frequency direction and at intervals of 4 symbols in the time direction, specifically, in the first symbol, the pilot signals are 1, 9, 73, 137, ... , 841, 905, 913th carrier position, in the second symbol, the pilot signal is placed at 1, 25, 89, 153, ..., 857, 913th carrier position, the third symbol In, the pilot signal is arranged at the carrier position 1, 41, 105, 169, ..., 873, 913, and in the fourth symbol, the pilot signal is 1, 57, 121, 185, ..., 889. , 913th carrier position, and in the fifth symbol, when the pilot signal is arranged at the 1, 9, 73, 137, ..., 841, 905, 913th carrier position, the predetermined carrier. The interval is 16 carrier intervals, and the carrier interval between the second carrier and the first carrier adjacent to the second carrier is 8 carrier intervals.

FIG. 6 schematically shows an OFDM receiver 60 according to this embodiment. As shown in FIG. 6, the OFDM receiver 60 includes an antenna 61, an amplifier 62, a band limiting filter 63, a frequency converter 64, an analog-to-digital converter (ADC) 65, and an OFDM symbol synchronization unit 66. , Fast Fourier Transform (FFT) unit 67, and signal equalization unit 68.

The antenna 61 receives an OFDM signal transmitted by an OFDM transmitter such as the OFDM transmitter 40 shown in FIG. The OFDM signal received by the antenna 61 is amplified by the amplifier 62, passes through the band limiting filter 63, is frequency-converted by the frequency conversion unit 64, and is converted into a digital signal by the ADC 65. After that, the OFDM symbol synchronization unit 66 removes the guard interval, the FFT unit 67 converts the signal in the time domain into a signal in the frequency domain, and gives the signal to the signal equalization unit 68. The signal equalization unit 68 detects the pilot signal included in the received signal, estimates the transmission line characteristics based on the detected pilot signal, and performs waveform equalization on the received signal based on the estimation result. In this way, data in which transmission line distortion is removed or reduced can be obtained.

FIG. 7 schematically shows a configuration example of the signal equalization unit 68 shown in FIG. The signal equalization unit 68 can be implemented by, for example, an application specific integrated circuit (ASIC), an LSI (Large-Scale integration) circuit, a DSP (Digital Signal Processor), or the like.

As shown in FIG. 7, the signal equalization unit 68 includes a data buffer 71, a complex division unit 72, a pilot extraction unit 73, and a frequency direction interpolation unit 75. The frequency domain signal output from the FFT unit 67 (FIG. 6) is input to the data buffer 71 and the pilot extraction unit 73. The data buffer 71 temporarily stores the signal in the frequency domain and passes it to the complex division unit 72 at an appropriate timing. The pilot extraction unit 73 extracts a pilot signal from the signal in the frequency domain. Further, the pilot extraction unit 73 calculates the transmission line characteristics of the carrier on which the pilot signal is arranged from each extracted pilot signal. The transmission line characteristics are calculated by comparing the extracted pilot signal with a known pilot signal. The frequency direction interpolation unit 75 performs an interpolation interpolation process using an FIR filter based on the transmission line characteristics calculated by the pilot extraction unit 73 for each symbol, whereby a third carrier (pilot signal is arranged). Estimate the transmission line characteristics of no carrier). The complex division unit 72 complex-divides the signal received from the data buffer 71 for each symbol and each carrier by the transmission line characteristics estimated by the frequency direction interpolation unit 75.

In the embodiment in which the SP is used as the pilot signal, the signal equalization unit 68 further includes a time direction interpolation unit 74. The time direction interpolation unit 74 is provided between the pilot extraction unit 73 and the frequency direction interpolation unit 75. The time direction interpolation unit 74 transmits by performing interpolation processing using an interpolation filter based on the transmission line characteristics calculated by the pilot extraction unit 73 for each carrier in which pilot signals are arranged at regular intervals in the time direction. Calculate road characteristics. After that, the frequency direction interpolation unit 75 performs the frequency direction interpolation processing based on the result of the time direction interpolation processing by the time direction interpolation unit 74.

FIG. 8 schematically shows a configuration example of the frequency direction interpolation unit 75. As shown in FIG. 8, the frequency direction interpolation unit 75 includes a data buffer 81, a correction pilot extraction unit 82, a correction pilot removal unit 83, a signal switching unit 84, an FIR filter 85, a difference calculation unit 86, and a pilot signal correction. A unit 87 is provided.

In FIG. 8, the transmission line characteristics calculated by the pilot extraction unit 73 (FIG. 7) are input to the data buffer 81. The data buffer 81 temporarily stores the transmission line characteristics calculated by the pilot extraction unit 73, and passes them to the correction pilot extraction unit 82, the correction pilot removal unit 83, and the pilot signal correction unit 87 at an appropriate timing. The correction pilot extraction unit 82 extracts the correction pilot signal from the pilot signal extracted by the pilot extraction unit 73 (FIG. 7). Specifically, the correction pilot extraction unit 82 extracts the transmission line characteristics of the second carrier (carrier on which the correction pilot signal is arranged) calculated by the pilot extraction unit 73. According to the example of FIG. 5, the correction pilot extraction unit 82 extracts the transmission line characteristics of the first and 913th carriers calculated by the pilot extraction unit 73.

The correction pilot removing unit 83 removes the correction pilot signal from the pilot signal extracted by the pilot extraction unit 73. Specifically, the correction pilot removing unit 83 uses the transmission line characteristics of the first and second carriers (carriers on which the pilot signal is arranged) calculated by the pilot extraction unit 73 to determine the transmission line of the second carrier. Remove the property. According to the example of FIG. 5, the correction pilot removing unit 83 extracts the transmission line characteristics of the 9, 25, 41, ..., 889, 905th carriers calculated by the pilot extraction unit 73. For example, the transmission line characteristics of the 1st and 913th carriers are set to zero. The signal switching unit 84 selectively switches between the correction pilot removal unit 83 and the pilot signal correction unit 87, and passes the signal from the correction pilot removal unit 83 to the FIR filter 85, or the signal from the pilot signal correction unit 87. Is passed to the FIR filter 85. When the correction pilot removal unit 83 is selected by the signal switching unit 84, interpolation processing using the FIR filter 85 is performed based on the transmission line characteristics from the correction pilot removal unit 83, and the third carrier The transmission line characteristics are estimated. This corresponds to the "actual response" shown in FIG. At this time, it is not necessary to obtain the filter response for all carriers. The transmission line characteristics of the second carrier (the first and 913th carriers in the example of FIG. 5) may be calculated, and the calculation may be terminated at about 60 carriers from the band end, for example.

The difference calculation unit 86 calculates the difference between the transmission line characteristics of the second carrier calculated by the pilot extraction unit 73 and the transmission line characteristics of the second carrier estimated by using the FIR filter 85. This difference corresponds to M shown in FIG. The difference is calculated for each of the lower and upper ends of the transmission band (first and 913th carriers in the example of FIG. 5).

The pilot signal correction unit 87 is a virtual carrier located out of the band at a predetermined carrier interval from the first carrier adjacent to the second carrier based on the difference calculated by the difference calculation unit 86 (example of FIG. 5). Then, the transmission line characteristics of the -7th and 921st carriers) are estimated. For example, the transmission line characteristics of the virtual carrier are estimated according to the above mathematical formula (1). The pilot signal correction unit 87 outputs the estimated transmission line characteristics of the virtual carrier and the transmission line characteristics of the first carrier calculated by the pilot extraction unit 73 to the FIR filter 85 via the signal switching unit 84. When the pilot signal correction unit 87 is selected by the signal switching unit 84, it is based on the transmission line characteristics of the virtual carrier estimated by the pilot signal correction unit 87 and the transmission line characteristics of the first carrier calculated by the pilot extraction unit 73. Then, the interpolation interpolation process using the FIR filter 85 is performed, and the transmission line characteristics of the third carrier are estimated. The transmission line characteristics obtained in this way are output to the complex division unit 72 (FIG. 7).

As described above, in the OFDM signal according to the present embodiment, the pilot signals are arranged on the plurality of first carriers located at predetermined carrier intervals and the second carriers located at both ends of the band, and the second carrier and the second carrier are arranged. The carrier interval between the first carrier adjacent to the second carrier is smaller than the predetermined carrier interval. The OFDM receiver calculates the transmission line characteristics of the first carrier based on the pilot signal of the first carrier, and calculates and calculates the transmission line characteristics of the second carrier based on the pilot signal of the second carrier. Based on the transmission line characteristics of the first carrier, the insertion / interpolation processing in the frequency direction using the interpolation filter is performed to estimate the transmission line characteristics of the second carrier. Further, the OFDM receiver calculates the difference between the calculated transmission line characteristics of the second carrier and the estimated transmission line characteristics of the second carrier, and is adjacent to the first carrier based on the difference. The transmission line characteristics of virtual carriers located outside the band at a predetermined carrier interval from the first carrier are estimated, and based on the calculated pilot signal of the first carrier and the estimated transmission line characteristics of the virtual carrier. By applying the interpolation filter, the transmission line characteristics of the carrier on which the pilot signal is not arranged are estimated. In this way, by adding the pilot signal of the second carrier, it is possible to correct the transmission line characteristics, and as a result, the transmission line characteristics can be estimated accurately even at the band end.

The above-described embodiment is an example, and the present invention is not limited to the configuration of the device or the like according to the above-described embodiment, and various configurations may be used. Further, various processes shown in the above-described embodiment may be executed by a hardware circuit, and a control program in which the processor is stored in a ROM (Read Only Memory) in a hardware resource including a processor and a memory is used. It may be controlled by executing.

40 ... OFDM transmitter, 41 ... OFDM frame generator, 42 ... Correction pilot insertion section, 43 ... IFFT section, 44 ... Bandwidth limiting filter, 46 ... Frequency transform section, 47 ... Amplifier, 48 ... Antenna, 60 ... OFDM reception Machine, 61 ... Antenna, 62 ... Amplifier, 63 ... Band limiting filter, 64 ... Frequency transform section, 66 ... OFDM symbol synchronization section, 67 ... FFT section, 68 ... Signal equalization section, 71 ... Data buffer, 72 ... Complex division Unit, 73 ... Pilot extraction unit, 74 ... Time direction interpolation unit, 75 ... Frequency direction interpolation unit, 81 ... Data buffer, 82 ... Correction pilot extraction unit, 83 ... Correction pilot removal unit, 84 ... Signal switching unit, 85 ... FIR filter, 86 ... Difference calculation unit, 87 ... Pilot signal correction unit.

Claims (3)

Pilot signals are arranged on a plurality of first carriers located at predetermined carrier intervals and second carriers located at both ends of the band, and the second carrier and the first carrier adjacent to the second carrier are arranged. An OFDM receiver that receives orthogonal frequency division multiplexing (OFDM) signals whose carrier spacing is smaller than the predetermined carrier spacing.
A means for calculating the transmission line characteristics of the plurality of first carriers based on the pilot signals of the plurality of first carriers, and
A means for calculating the transmission line characteristics of the second carrier based on the pilot signal of the second carrier, and
A means for estimating the transmission line characteristics of the second carrier by performing interpolation processing in the frequency direction using an interpolation filter based on the calculated transmission line characteristics of the plurality of first carriers.
A means for calculating the difference between the calculated transmission line characteristics of the second carrier and the estimated transmission line characteristics of the second carrier, and
A means for estimating the transmission line characteristics of a virtual carrier located outside the band with a predetermined carrier interval from the adjacent first carrier based on the calculated difference.
By applying the interpolation filter based on the calculated pilot signals of the plurality of first carriers and the estimated transmission line characteristics of the virtual carriers, the carriers to which the pilot signals are not arranged Means for estimating transmission line characteristics and
An OFDM receiver comprising. The OFDM receiver according to claim 1, wherein the carrier interval between the second carrier and the adjacent first carrier is at least half of the predetermined carrier interval. Pilot signals are arranged on a plurality of first carriers located at predetermined carrier intervals and second carriers located at both ends of the band, and the second carrier and the first carrier adjacent to the second carrier are arranged. An OFDM reception method performed by an OFDM receiver that receives an orthogonal frequency division multiplexing (OFDM) signal in which the carrier interval between the carriers is smaller than the predetermined carrier interval.
The transmission line characteristics of the plurality of first carriers are calculated based on the pilot signals of the plurality of first carriers.
The transmission line characteristics of the second carrier are calculated based on the pilot signal of the second carrier.
Based on the calculated transmission line characteristics of the plurality of first carriers, interpolation processing in the frequency direction using an interpolation filter is performed to estimate the transmission line characteristics of the second carrier.
The difference between the calculated transmission line characteristics of the second carrier and the estimated transmission line characteristics of the second carrier is calculated.
Based on the calculated difference, the transmission line characteristics of the virtual carrier located outside the band with the predetermined carrier interval from the adjacent first carrier are estimated.
By applying the interpolation filter based on the calculated pilot signals of the plurality of first carriers and the estimated transmission line characteristics of the virtual carriers, the carriers to which the pilot signals are not arranged Estimate transmission line characteristics,
An OFDM reception method characterized by that.