JP2001186104A - Orthogonal multicarrier signal transmitter, transmission method for orthogonal multicarrier signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an inverse discrete Fourier arithmetic method using a small circuit scale by reducing an arithmetic quantity for inverse discrete Fourier transforms, having a large number of points to generate an intermittent type orthogonal multicarrier signal. SOLUTION: In the case of generating intermittent type orthogonal multicarrier signals, where information is transmitted with 16 carriers in total at an interval of 4 carriers, 16-point IDFT transform is conducted, the result is utilized for 64-point IDFT transform, and the 64-point IDFT transform is calculated by 5th and 6th stages that are the latter half of a 64-point IDFT arithmetic unit. Thus, the IDFT transform is conducted with less number of points than that of a conventional method in the first half, that is, from the 1st to the 4th stages and the desired intermittent type orthogonal multicarrier signals can be generated in the arithmetic method adopting a smaller circuit scale.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transmitting a digitally modulated signal for transmission by an orthogonal frequency division multiplexing (OFDM) method and a transmission method thereof, and more particularly, to a quadrature in which the frequency of a modulated signal is intermittent. Multi-carrier signals
In particular, the present invention relates to an apparatus for generating a signal using an IFFT having a simple configuration, and a method for generating a signal for transmitting the orthogonal multicarrier signal.

[0002]

2. Description of the Related Art When a digital information signal is transmitted, a carrier of a single frequency (carrier) is phase-modulated (PSK) or quadrature amplitude-modulated (QAM) based on digital information.
A method of converting the obtained signal into a high-frequency signal, and radiating and transmitting the signal as a radio wave is widely known. The phase modulation (PSK) system is a system in which a digital information signal to be transmitted is modulated according to the phase component of a carrier wave and transmitted. The quadrature amplitude modulation (QAM) system uses both the phase and amplitude of the carrier wave. Modulation method.

On the other hand, recently, as a new transmission method, orthogonal frequency division multiplexing (OFDM) has been proposed.
A multicarrier transmission method called an ivision multiplexing method has been proposed. This OFDM system relates to a system in which a plurality of orthogonal carriers are generated and arranged in a transmission band, and each carrier is subjected to phase modulation or quadrature amplitude modulation.

[0004] The "carriers are orthogonal" means that the spectrum of an adjacent carrier becomes zero at the frequency position of the carrier, and signals transmitted by being modulated by a plurality of carriers constituting the OFDM are mutually transmitted. Means that transmission is possible independently without interference.

In this OFDM system, since a number of carriers are used for transmission, the modulation speed of each carrier can be reduced as compared with transmission using a carrier of a single frequency. Since the influence of the interference due to the distortion can be reduced and the spectrum of the modulated signal can be made rectangular, the occupied bandwidth can be narrowed and the frequency can be efficiently used.

In order to reduce interference distortion due to multipath distortion in a spatial transmission path, a buffer time is provided by a guard interval longer than the delay time of a delay wave serving as interference distortion to reduce interference distortion. Since the temporal relative ratio occupied by the guard interval signal transmitted as a redundant signal has a low modulation speed, it can be reduced. For example, interference distortion can be reduced while keeping the transmission efficiency from decreasing.

As described above, the OFDM system has excellent transmission characteristics in a multipath environment, and has been determined to be used as a terrestrial digital broadcast transmission system. On the transmitting side of the OFDM system used in the terrestrial digital broadcasting system, an IDFT transform (inverse discrete Fourier transform) is used to generate an OFDM signal, that is, an orthogonal multicarrier signal. This is a method of generating a modulation signal by changing the information to be transmitted by changing the phase and amplitude components of each carrier, and the phase given to each orthogonal carrier,
The frequency domain signal which is the amplitude modulation signal information is IDFT
Transformation into time domain signals, the time domain signals are added and synthesized, and the OF
The DM signal is converted into a high-frequency signal and emitted from the antenna.

The reception of this radiated OFDM signal is D
The above-mentioned time-domain signal is converted into a frequency-domain signal by an FT (Discrete Fourier Transform) circuit, and the orthogonal frequency-multiplexed time-domain signal is converted into a carrier phase and amplitude modulation signal by the DFT. Information is converted as a signal in the frequency domain, and information to be transmitted is decoded based on the converted signal.

This DFT signal processing is realized by a DSP (Digital Signal Processor) or by converting a signal processing circuit into an LSI (Large Scale Integrated Circuit). As a result, the signal processing can be realized at a relatively high speed, so that the signal processing of the OFDM system is facilitated and the practical use thereof has been realized.

In transmission of such an OFDM signal, that is, an orthogonal multicarrier signal, it is general that a plurality of channels or a plurality of users perform broadcasting and communication by dividing a frequency band to be transmitted to each other. In digital terrestrial broadcasting, channels each having a bandwidth of 6 MHz are aligned and arranged with a frequency buffer area serving as a guard band interposed therebetween.

Each carrier of the OFDM signal thus formed exists at a frequency interval given by a reciprocal of a symbol period, that is, a period obtained by adding a guard interval period to a window time period for performing IDFT conversion. An information signal is transmitted using all these carriers.

For example, each carrier transmitted by digital terrestrial broadcasting is arranged at a frequency interval of about 1 kHz to 4 kHz, and an information signal is transmitted using all the carriers.

As described above, the OFDM system is used not only in the broadcasting field, but also in the communication field, for example, in a wireless LAN system. In the communication field, in particular, multipath is used due to the reflection of radio waves by the wall surface of an object. It has the advantage that stable transmission characteristics can be obtained even in an indoor environment where a large amount of distortion occurs, and its use has recently been increasing.

FIG. 26 shows a configuration of a multi-carrier transmission apparatus generated by the OFDM method. The multi-carrier transmission apparatus 130 shown in FIG. 1 includes a multi-carrier transmission apparatus 134 including an input circuit section 140 and an OFDM transmission section 150, and a multi-carrier reception apparatus including an OFDM reception section 160 and an output circuit section 180. 13
6.

In FIG. 1, an information signal to be transmitted is supplied to an input circuit 140, where an information signal to which an error correction code is added is supplied to an OFDM transmission section 150.

Here, a multicarrier signal is generated by an inverse discrete Fourier transform circuit described later, and a radio wave radiated through an antenna (not shown) is received by an antenna (not shown) and supplied to an OFDM receiver 160 to be decoded. The decoded signal is supplied to an output circuit unit 180, where an error signal is detected and corrected, and the transmitted information signal is supplied as an information signal output from a multicarrier receiving unit 136.

FIG. 27 is a block diagram showing an example of a conventional multicarrier signal transmitting apparatus. The OFDM transmission unit 150 shown in FIG.
A converter 54, quadrature modulator 55, signal generators 56, 90
° shifter 57, frequency converter 58, and transmission unit 59.

An information signal to be transmitted is supplied to an input circuit 42 via an information signal input terminal 41. Here, an error correction signal or the like is added, and a modulation method of the information signal is assigned to a generated carrier frequency. The signal for the real part and the signal for the imaginary part allocated in this way are supplied to the arithmetic unit 151.

The signal supplied to the operation unit 151 is
The multi-carrier modulation signal corresponding to the information signal input supplied from the input circuit is generated by arithmetic processing by T (Inverse Fast Fourier Transform), and the generated real part and imaginary part signals are output to the output buffer 53. Supplied to Here, these IFFT-calculated signals are temporarily stored, and the stored signals are supplied to the D / A converter 54.

Here, the signal supplied in the form of a digital signal is converted into an analog signal by a D / A converter,
Unnecessary high frequency components are removed by F to obtain a modulated signal component, and the signal is supplied to the quadrature modulator 55.

Here, the real part and imaginary part signals supplied from the D / A converter are provided by the intermediate frequency supplied from the signal generator 56 and the intermediate frequency whose phase is changed by 90 ° by the 90 ° shifter. Is quadrature-modulated, the quadrature-modulated intermediate frequency signal is converted by a frequency converter 58 into a frequency to be radiated to a spatial transmission path, and the frequency-converted signal is power-amplified by a transmission unit 59, and is transmitted through an antenna (not shown). Radiated to the spatial transmission path.

FIG. 28 shows a block diagram of a multicarrier receiving apparatus. The OFDM receiving section 160 in the figure includes a receiving section 61, a frequency converter 62, an intermediate frequency amplifier 63,
It comprises a quadrature demodulator 64, a synchronization signal generation circuit 65, a 90 ° shifter 66, an LPF 67, an A / D converter 68, a guard interval period processing circuit 69, and a decoding circuit 170.

To explain the operation of the multi-carrier receiving device 136, the signal transmitted via the spatial transmission path is
The signal is received by an antenna (not shown) and supplied to the receiving unit 61. Here, high-frequency amplification is performed, and the amplified signal is supplied to a frequency converter 62 and converted into an intermediate frequency.
The converted signal is supplied to an intermediate frequency amplifier 63 and amplified, and the amplified signal is supplied to a quadrature demodulator 64.

Here, the amplitude demodulation is performed on the basis of the signal of the intermediate frequency supplied from the synchronizing signal generation circuit 65 and the signal which is shifted by 90 ° by the 90 ° shifter, and the amplitude is demodulated by each signal. The converted signal is supplied to the A / D converter 68 via the LPF 67 and is converted into a digital signal. The signal converted into the digital signal is subjected to a guard interval period processing circuit to remove the signal in the guard interval period. The obtained signal is supplied to the decoding circuit 170.

Here, the supplied real part and imaginary part signals are subjected to high-speed discrete Fourier transform, and signal components corresponding to the real part and imaginary part of each carrier frequency are obtained.
The obtained signal component is transmitted to the multicarrier transmitting apparatus 1
The QAM signal is decoded based on the modulation signal assignment performed by the 34 operation unit 151, and the decoded signal is supplied to the output circuit 81.

Here, the error signal is corrected based on the error correction signal added by the input circuit 42, and the demodulated output signal obtained in this manner is supplied to the output terminal 82.

In this manner, a multicarrier signal is generated, transmitted, and received. The number of frequencies used as the multicarrier is 256, 1024, or more. Thus, a large number of carriers can be easily generated by the IDFT circuit. For example, 1
In order to generate 024 carriers, an IDFT having 1024 points or more points is used, and is output as a time-series signal from the IDFT.

The multicarrier signal generated as described above is transmitted using all orthogonal carrier frequencies in an orthogonal relationship in the frequency band used for the transmission. A transmission method in which a carrier is intermittently used for transmission instead of using all carriers constituting the carrier will be described.

In the transmission method using the carrier intermittently, since the carrier for transmission is intermittently arranged, the transmission is performed using a wider transmission band, for example, in a local frequency domain. Even if the transmission path deteriorates, it is easy to correct the error data to correct data with an error correction circuit, such as by reducing the number of affected carriers because the spacing between adjacent carriers is wide. Yes, and excellent transmission characteristics can be obtained.

For a wireless device or the like that transmits a weak signal, in order to reduce interference with electronic equipment installed in the vicinity, a method of reducing the transmission power in a 1 MHz band is used. The orthogonal multi-carrier signal transmitted intermittently using every other wave is transmitted over a wider frequency band than when all carriers arranged at small frequency intervals are transmitted. It is characterized in that the density can be reduced and the electromagnetic interference applied to the surrounding electronic devices can be reduced.

As described above, in connection with the transmission method of intermittently arranging the carrier waves, Japanese Patent Application No. 10-277103.
A "method of generating and decoding an orthogonal multicarrier signal" is proposed.

When a carrier is used intermittently in the proposed method of generating an orthogonal multicarrier signal, for example, for each of integer values L and M larger than 2 and integer values N larger than 4, In the intermittent orthogonal multi-carrier system in which N carriers are selected every L carriers and M selected carriers are used, it is necessary to generate N carriers in total, and there is an N orthogonal relationship. A signal is generated using at least N points or more of IDFT transforms for generating a carrier wave. Here, N at this time
The IDFT of the point or more modulates only one of the L carriers with information data and transmits the remaining (L
-1) The carrier wave is modulated by giving data to make the amplitude zero, so that the carrier wave is not generated.

The IFFT circuit used in this way is
An IDFT operation circuit of N = L × M points or more is required, and an IFFT circuit having such a large number of points can be realized by a large-scale semiconductor integrated circuit (LSI) or a high-speed digital signal processor (DSP). However, as the number of points of the IDFT circuit increases, the circuit size of the IDFT circuit also increases. When this is realized by a large digital signal processor having a large number of signal processing points and a large amount of computation, a high cost configuration is required. There was a problem that would be.

[0034]

By the way, the signal transmission in the above-described conventional multi-carrier transmission apparatus 130 is based on the premise that it operates using all carrier frequencies generated by the IDFT circuit. Met.

The multi-carrier transmission apparatus to which the present invention is directed is one in which the multi-carriers radiated to the spatial transmission path are intermittently arranged. A signal transmission device having characteristics such as "Signal generation method and decoding method", wherein intermittently arranged orthogonal multicarrier generation is realized by IFFT (Inverse Fast Fourier Transform) having as few arithmetic processing times as possible. It is an object.

Further, the above-described transmitting apparatus generates a multicarrier signal for an input signal of one channel. For example, a transmitting apparatus capable of simultaneously transmitting information signals of four or eight channels is provided by an IFFT having a simple configuration. This is to be realized by a circuit.

[0037]

The present invention comprises the following means 1) to 6) to solve the above-mentioned problems. That is,

1) Inverse discrete Fourier transform of a digital information signal to be transmitted to generate an orthogonal multicarrier signal,
A transmitting side that outputs a transmission signal based on the generated orthogonal multicarrier signal to a transmission line, and a quadrature multicarrier signal obtained by demodulating a transmission signal received from the transmission line with the inverse discrete Fourier transform of the transmission side. An orthogonal multi-carrier signal transmission apparatus for use in an information transmission system having a receiving side for reproducing the digital information signal by performing a discrete Fourier transform and generating an orthogonal multi-carrier signal on a transmitting side, wherein the inverse discrete Fourier transform A first inverse discrete Fourier transform means (51a) for performing an inverse discrete Fourier transform of M points for an integer value M greater than 2 which is in charge of the digital information signal to be transmitted and transmitted, A signal which is in charge of the latter half of the Fourier transform and which is output from the first inverse discrete Fourier transform means. A second inverse discrete Fourier transform means (52) for performing an inverse Fourier transform of N points for an integer value N larger than twice M to output the orthogonal multicarrier signal, and a second inverse discrete Fourier transform High-frequency signal generating means (mainly 55, 58) for converting the orthogonal multi-carrier signal into a high-frequency signal in order to supply the orthogonal multi-carrier signal output from the means to the transmission line
An orthogonal multi-carrier signal transmission device comprising:

2) A digital information signal of a plurality of channels to be transmitted is subjected to inverse discrete Fourier transform to generate an orthogonal multicarrier signal, and a transmitting side for outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path. And a receiving side that reproduces the digital information signals of the plurality of channels by performing a discrete Fourier transform complementarily to the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the transmission path. An orthogonal multicarrier signal transmission device that is used in a transmission system and generates an orthogonal multicarrier signal on a transmission side,
A plurality of first inverse discrete Fourier transforms that are responsible for the first half stage of the inverse discrete Fourier transform and that are supplied with the digital signals of the plurality of channels to be transmitted and perform M-point inverse discrete Fourier transform for an integer value M greater than 2 Means (51a-51d), and a second half of the inverse discrete Fourier transform, and outputs each signal output from the plurality of first inverse discrete Fourier transform means to an integer value N larger than twice M. Second inverse discrete Fourier transform means (52) for performing inverse Fourier transform of points to output the orthogonal multicarrier signal, and transmitting the orthogonal multicarrier signal output from the second inverse discrete Fourier transform means to the transmission line High-frequency signal generating means (mainly 55 58) and quadrature multi-carrier signal transmitting apparatus characterized by comprising a.

3) Inverse discrete Fourier transform of a digital information signal to be transmitted to generate an orthogonal multicarrier signal,
A transmitting side that outputs a transmission signal based on the generated orthogonal multicarrier signal to a transmission line, and a quadrature multicarrier signal obtained by demodulating a transmission signal received from the transmission line with the inverse discrete Fourier transform of the transmission side. An orthogonal multi-carrier signal transmission apparatus for use in an information transmission system having a receiving side for reproducing the digital information signal by performing a discrete Fourier transform and generating an orthogonal multi-carrier signal on a transmitting side, wherein the inverse discrete Fourier transform A first discrete discrete Fourier transform that provides the digital signal to be transmitted and is supplied with the digital signal to be transmitted, and performs an inverse discrete Fourier transform of M points for an integer value M greater than 2 using a twiddle factor corresponding to a desired transmission channel. Conversion means (5
1a) and the second stage of the inverse discrete Fourier transform, and outputting the signal output from the first inverse discrete Fourier transform means to an integer N greater than twice M
A second inverse discrete Fourier transform means (5) for performing an inverse Fourier transform of the points and outputting the orthogonal multicarrier signal;
2) and high-frequency signal generation means (mainly 55) for converting the orthogonal multicarrier signal into a high-frequency signal in order to supply the orthogonal multicarrier signal output from the second inverse discrete Fourier transform means to the transmission line. , 58). An orthogonal multicarrier signal transmission apparatus, comprising:

4) Inverse discrete Fourier transform of the digital information signal to be transmitted to generate an orthogonal multicarrier signal,
A transmitting side that outputs a transmission signal based on the generated orthogonal multicarrier signal to a transmission line, and a quadrature multicarrier signal obtained by demodulating a transmission signal received from the transmission line with the inverse discrete Fourier transform of the transmission side. An orthogonal multi-carrier signal transmission apparatus for use in an information transmission system having a receiving side for reproducing the digital information signal by performing a discrete Fourier transform and generating an orthogonal multi-carrier signal on a transmitting side, wherein the inverse discrete Fourier transform A first inverse discrete Fourier transform means (51a) for performing an inverse discrete Fourier transform of M points for an integer value M greater than 2 in response to the digital signal to be transmitted and transmitted, A signal which is in charge of the latter half of the transformation and which is output from the first inverse discrete Fourier transform means. A second inverse discrete Fourier transform of an N-point inverse Fourier transform for an integer value N greater than twice M, which is supplied to an input terminal corresponding to a desired transmission channel, performs an arithmetic operation, and outputs the orthogonal multicarrier signal. Means (52), and a high-frequency signal generating means (mainly for converting the orthogonal multi-carrier signal into a high-frequency signal in order to supply the orthogonal multi-carrier signal output from the second inverse discrete Fourier transform means to the transmission path) 55, 58)
An orthogonal multi-carrier signal transmission device comprising:

5) Inverse discrete Fourier transform of a digital information signal to be transmitted to generate an orthogonal multicarrier signal,
A transmitting side that outputs a transmission signal based on the generated orthogonal multicarrier signal to a transmission line, and a quadrature multicarrier signal obtained by demodulating a transmission signal received from the transmission line with the inverse discrete Fourier transform of the transmission side. An orthogonal multicarrier signal transmission method for generating an orthogonal multicarrier signal on a transmission side, the method being used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform, wherein the inverse discrete Fourier transform A first inverse discrete Fourier operation step of performing the inverse discrete Fourier transform of M points for an integer value M greater than 2 in charge of the digital information signal to be transmitted and transmitted, A signal that is in charge of a second half stage and that is output from the first inverse discrete Fourier calculation step , M, and an N-point inverse Fourier transform for an integer value N greater than twice M to output the orthogonal multi-carrier signal, and output from the second inverse discrete Fourier transform step. A high-frequency signal generating step of converting the orthogonal multicarrier signal into a high-frequency signal in order to supply the orthogonal multicarrier signal to the transmission path.

6) Inverse discrete Fourier transform of the digital information signal to be transmitted to generate an orthogonal multicarrier signal,
A transmitting side that outputs a transmission signal based on the generated orthogonal multicarrier signal to a transmission line, and a quadrature multicarrier signal obtained by demodulating a transmission signal received from the transmission line with the inverse discrete Fourier transform of the transmission side. An orthogonal multicarrier signal transmission method for generating an orthogonal multicarrier signal on a transmission side, the method being used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform, wherein the inverse discrete Fourier transform A first discrete discrete Fourier transform that provides the digital signal to be transmitted and is supplied with the digital signal to be transmitted, and performs an inverse discrete Fourier transform of M points for an integer value M greater than 2 using a twiddle factor corresponding to a desired transmission channel. An operation step and a second half stage of the inverse discrete Fourier transform, and The signal output from the discrete Fourier transform means, and a second inverse discrete Fourier transform step of outputting the quadrature multi-carrier signal by performing inverse Fourier transform of N points for large integer N than twice M,
A high-frequency signal generating step of converting the orthogonal multicarrier signal into a high-frequency signal in order to supply the orthogonal multicarrier signal output from the second inverse discrete Fourier transform step to the transmission path. An orthogonal multicarrier signal transmission method.

[0044]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an orthogonal multicarrier signal transmission apparatus according to an embodiment of the present invention. FIG. 1 is a schematic block diagram of a multi-carrier transmission device adopting the multi-carrier generation method. In FIG. 1, a multi-carrier transmission apparatus 30 inputs four channels of information signals a to d to be transmitted and converts the information signals to OFDM (Or
A multi-carrier transmitting apparatus 34 that obtains a modulated output signal modulated by a thogonal frequency division multiplexing (radio frequency division multiplexing) method and radiates the signal from a transmitting antenna to a spatial transmission path, and obtains a signal from the spatial transmitting path by a receiving antenna and supplies the obtained signal. , Demodulates and decodes the signal to obtain information signal outputs of four channels a to d.
It is composed of

Here, the multi-carrier transmitting device 34
Input circuit units 40a to 40 for inputting information of four channels
d, and an OFDM transmitting unit 50, and the multi-carrier receiving device 36 includes OFDM receiving units 60 and 4
Output circuits 80a to 80 for supplying demodulated outputs of channels
d.

The operation of the multi-carrier transmission apparatus 30 shown in FIG.
ing Picture Experts Group -2), the signal of the bit stream compressed and coded by the information signal input terminals a to
d to input circuits 40a to 40d, where these circuits add error detection, correction codes, and the like, and the signals of the respective input circuits are supplied to the OFDM transmission unit 50.

Here, the information signal to be transmitted to which the error correction code is added is OFD in a predetermined format described later.
The signal is modulated into a DM signal and transmitted through a spatial transmission path, and the transmitted signal is supplied to an OFDM receiver 60.

Here, the OFDM signal is demodulated, and the demodulated signal is supplied to respective output circuits 80a to 80d. These output circuits 80a to 80d detect an error signal for each carrier constituting the OFDM signal based on the error detection code added by each of the input circuits 40a to 40d, and correct each error signal. The information signal output is supplied from the multi-carrier receiving device 36.

Next, the configurations and operations of the multicarrier transmitting device 34 and the multicarrier receiving device 36 will be described in detail. FIG. 2 shows a multicarrier transmission device 34.
Is shown.

In the figure, information signals of four channels are supplied to input terminals 41a to 41d, respectively, and these signals are supplied to input circuit units 42a to 42d.
In these circuits, an error correction code is added to each supplied signal to generate a signal divided into a real part and an imaginary part signal for modulating a multicarrier, and the signal is divided into first to fourth signals. It is supplied to the computing units 51a to 51d.

The signals of the first to fourth arithmetic units 51a to 51d are supplied to a subsequent-stage arithmetic unit 52, and these arithmetic units perform IFFT arithmetic processing by a method described later.
In accordance with the information signals supplied to the input terminals 41a to 41d, modulated quadrature multicarrier signals are generated, and the signals are supplied to a D / A converter 54 via an output buffer 53.

Here, the signal supplied in the form of a digital signal is converted into an analog signal by a D / A converter,
Unnecessary high frequency components are removed by the PF, and a modulated signal is obtained. The modulated signal is supplied to the quadrature modulator 55.

Here, the real frequency and the imaginary frequency signals supplied from the D / A converter are provided by the intermediate frequency supplied from the signal generator 56 and the intermediate frequency whose phase is changed by 90 ° by the 90 ° shifter. Is quadrature-modulated, the quadrature-modulated intermediate frequency signal is converted to a frequency radiated to the spatial transmission path by the frequency converter 58, and the signal is power-amplified by the transmission unit 59 and supplied to an antenna (not shown). It is radiated from the antenna to the space transmission line.

FIG. 3 shows a block diagram of a multicarrier receiving apparatus. In the figure, a multi-carrier receiving device 3
6 is a receiving unit 61, a frequency converter 62, an intermediate frequency amplifier 6
3, an orthogonal demodulator 64, a synchronization signal generation circuit 65, a 90 ° shifter 66, an LPF 67, an A / D converter 68, a guard interval period processing circuit 69, and an OFDM reception unit 60 including a decoding circuit 70. Output terminal 8
2a to 82d, each output circuit 81a
~ 81d.

In addition, the operation of the multi-carrier receiving device 36 will be described. A signal transmitted via a spatial transmission path is received by an antenna (not shown), and the signal is supplied to a receiving unit 61. Here, high-frequency amplification is performed, and the amplified signal is supplied to a frequency converter 62 and converted to an intermediate frequency. The converted signal is supplied to an intermediate frequency amplifier 63 and amplified, and supplied to a quadrature demodulator 64. You.

Here, amplitude demodulation is performed based on the signal of the intermediate frequency supplied from the synchronization signal generating circuit 65 and the signal whose phase is shifted by 90 ° by the 90 ° shifter from the supplied signal of the intermediate frequency. The amplitude-demodulated signal of each signal is supplied to an A / D converter 68 via an LPF 67 and converted into a digital signal. The signal converted into a digital signal is converted into a signal in a guard interval period by a guard interval period processing circuit. Is removed, and the signal thus obtained is supplied to the decoding circuit 70.

Here, the supplied real part and imaginary part signals are subjected to discrete fast Fourier transform, and signal components corresponding to the real part and imaginary part of each carrier frequency are obtained.
The signal components obtained in this manner are subjected to decoding of the QAM signal based on the modulation signal assignment performed by the arithmetic unit 51 of the multicarrier transmission device 34, and the decoded signals are output from the output circuits 81a to 81a, respectively. 81d.

In these output circuits 81a to 81d, an error signal is detected based on the error correction signal added in each of the input circuits 42a to 42d, the error signal is corrected, and each of these processes is performed. The demodulated output signals are supplied to respective output terminals 82a to 82d.

Now, here, the multicarrier transmission apparatus 3
0 describes the carrier frequency used for transmission. FIG. 4 shows how a multicarrier channel is generated by the multicarrier transmitter 34.

In the figure, (A) shows a multicarrier composed of 64 frequencies having carrier numbers 0 to 63, and the manner in which the carrier is divided into four channels and transmitted is represented by the carrier frequency number. And (B0) to (B0) to
(B3) is the carrier number for each channel and the power distribution for it. The multicarriers shown here are arranged at intervals of 50 kHz, and the carriers allocated to each channel are 200 kHz.
Hz are arranged intermittently at intervals of Hz, and the channels a to d are assigned by the carriers thus allocated and arranged.
Is transmitted.

FIG. 5 shows the relationship between the channel numbers of orthogonal multicarriers generated by the multicarrier transmission apparatus in this embodiment and the carrier numbers for transmitting signals of the channels. The 64 carriers shown here are assigned as frequencies for transmitting the signals of channels a to d. Channel a has a carrier number that is a multiple of 4, and channel b has 2 added to a multiple of 4. A carrier number, a channel c is a carrier number obtained by adding 1 to a multiple of 4, and a channel d is a carrier number obtained by adding 3 to a multiple of 4, for transmitting the respective information signals a to d. Set as a carrier.

Here, the modulated signals for these multicarriers are generated by performing an IFFT (Inverse Fast Fourier Transform) operation by the first arithmetic unit 51a to the fourth arithmetic unit 51d and the post-stage arithmetic unit 52. The method will be described in detail.

First, the IFFT operation will be described with reference to FIG.
4 shows a signal flow diagram of the 4-point IFFT, and the operation of the IFFT will be outlined. In the figure, X shown on the left side

[0], X [2], X [1], X
[3] is a terminal for supplying an input signal in the frequency domain.

[0], x [1], x [2], x
[3] is a terminal for supplying an output signal in the time domain.

The direction of the arrow shown in the figure indicates the direction in which the signal is supplied. If a constant (twiddle factor) is shown near the arrow, multiply this constant to supply the signal in the direction of the arrow. I do. An arrow without a constant indicates that it is supplied by multiplying by 1, or that the signal is merely supplied. At the nodes marked with two arrows facing each other, the signals supplied by those arrows are added.

FIG. 7 shows a twiddle factor used in the calculation of the 4-point FFT. In the figure, a circle having a radius of 1 is shown in a complex plane in which the horizontal axis is the real axis and the vertical axis is the imaginary axis, and the intersections of this circle and the real axis are 1 and -1, respectively. , The intersection with the imaginary axis is j and −j. The number j is made -1 by squaring shown here, four coefficients W ₄ of ^0, W ₄ ^1, W ₄ ^2, the value of W ₄ ^3, respectively 1, j, -1, -j Is shown.

Next, using the 16-point IFFT,
An example of generating a book carrier will be described. FIG.
The terminal of the IFFT element having the IFFT calculation function of the point is shown, and a generation method thereof will be described. In the figure, 16 terminals shown on the left side correspond to 16 frequencies.
The input terminals in the frequency domain are the 16 terminals shown on the right side for outputting the result of the IFFT operation as the output signal in the time domain.

The input terminals X [1], X [5], X [X] of the four frequency domains of this IFFT element

[9] and X [13] are supplied with an information signal for giving multi-level modulation to the four carriers to be generated, and the other input terminals are connected to the ground so that no input signal is given. . As a result of the inverse Fourier operation performed by this IFFT element, the output terminal x

[0] to x [15] include the first, fifth, ninth, and first
3 are modulated and the output signal voltage value of the synthesized time series is x

It is output as a sample value to the terminals [0] to x [15].

FIG. 9 shows a signal flow diagram of the output data alignment type 8-point IFFT by time thinning. X shown on the left side of FIG.

[0], X [4], X
[2], X [6] X [1], X [5], X [3], X
[7] indicates an input signal in the frequency domain, and x shown on the right side

[0] to x [7] indicate output signals in the time domain.

The method of butterfly operation of the IFFT will be described. The direction of the arrow shown in the figure indicates the direction in which a signal is supplied, and a constant (twiddle factor, −
When 1) is indicated, this constant is multiplied to supply a signal in the direction of the arrow. Arrows without constants indicate that they are supplied by multiplying by 1, or that they simply supply a signal. At the nodes marked with two arrows facing each other, the signals supplied by those arrows are added.

FIG. 10 shows an example of the calculation of the 8-point IFFT.
The eight constant values (twiddle factors) used are shown. Smell
The horizontal axis is the real axis, and the vertical axis is the imaginary axis.
A circle with a diameter of 1 is shown, corresponding to a position on the circumference divided into eight equal parts
Eight coefficients W₈ ⁰, W₈ ¹, W ₈ ^Two, ..., W₈ ⁷of
The value is the twiddle factor used in the operation. 8 points mentioned above
IFFT calculates W out of these eight twiddle factors.₈ ⁰,
W₈ ¹, W₈ ^Two, W₈ ^ThreeAre used in the calculation.

FIG. 11 shows the operation performed by such a method.
2 shows a configuration inside a point IFFT calculator. The black circles shown in the figure are signal connection points, and four black circles connected at diagonal lines and located at the vertices of a quadrangle indicate that butterfly operation is performed by two intersecting lines connecting them. I have. 0, 8, 4, 12,... Shown on the left side of FIG.
The number 15 indicates the number of the input signal in the frequency domain,
The numbers 0, 1, 2,..., 15 shown on the right side of the drawing indicate the numbers of output signals in the time domain.

The numbers shown at the intersections of the two lines in the figure indicate the numbers of the twiddle factors used when performing butterfly computation. FIG. 12 shows the 16-point IFF
The twiddle factor used in the calculation of T is shown. In the figure,
The horizontal axis is the real axis, and the vertical axis is the imaginary axis.
Shown is a circle, the upper its circumference 16 so as to correspond to the equally divided positions, 16 coefficients _{^{W 16 0, W 1 6 1}} , W 16 2, ···, W
₁₆ ¹⁵ points represents the value of the twiddle factor, 16 point IFFT described above, these have used eight W ₁₆ ⁰ to _W-16 ^7. In FIG. 11 described above, the values of these twiddle factors are indicated by numbers 0 to 7 indicated by superscripts of the twiddle factors.

In this way, the IFFT operation repeatedly performs the butterfly operation. The order in which the operation is performed is called the first stage, the second stage, and the third stage from the left in column units. In the case of the 16-point IFFT, calculations up to the fourth stage are performed.

The description of the IFFT shown here includes:
Although it is necessary to describe the same coefficient as shown as -1 in FIG. 9 described above, the insertion of the coefficient of -1 is performed at the same place, and the IFFT calculation is performed including the coefficient.

Now, a description will be given of a method of calculating the IFFT for a multi-channel transmission device according to the first embodiment. FIG. 13 shows a 64-point IFFT calculation method. The 64-point IFFT shown here has a configuration in which the calculation results of the first to fourth stages performed by the 16-point IFFT are used, and then the fifth and sixth stages of butterfly calculations are performed.

That is, a, b, c, and d shown in FIG.
Each is a 16-point IFFT calculation, and the calculation of the fifth stage is performed using the calculation result, and the calculation of the sixth stage is performed using the calculation result of the fifth stage.

FIG. 14 shows the twiddle factors used in the calculation of the 64-point IFFT. In the figure, the circumference of radius 1 drawn in the complex plane is divided into 64 equal parts, and 64 coefficients W ₆₄ ⁰ , W ₆₄ ¹ , W ₆₄ ² ,... ,
The value of W ₆₄ ⁶³ have been established.

Here, the values of the twiddle factors W ₁₆ ⁰ , W ₁₆ ¹ , W ₁₆ ² , W ₁₆ ³ ,... Used for the _16- point IFFT operation are the twiddle factors W ₆ used for the 64-point IFFT operation. ^{_{4 0, W 64 4, W}} 64 8, W 64 12, the same value as ..., ^{_{i.e., W 16 0 = W 64 0}} , W 16 1 = W 64 4, W 16 2 = W 64 8, W
^{_{16 3 = W 64 12, W}} 16 4 = W 64 16, W 16 5 = W 64 20, W 16 6 =
^{_{W 64 24, W 16 7 =}} W 64 28, a, a described here,
The twiddle factor used by b, c, and d is a 64-point IFF
The first to fourth stages of the T operation are shown, but the twiddle factor used in the 64-point IFFT operation can be replaced by a 16-point IFFT twiddle factor.

That is, the twiddle factor at the first stage at 64 points is 0, the twiddle factor at the second stage is 0,16, and the twiddle factor at the third stage is 0,8,1.
6, 24, the twiddle factor in the fourth stage is 0, 4, 8, 1
2, 16, 20, 24, 28.

In FIG. 11, e and f are operations in the fifth stage, and the same operation is performed in e and f. Where I
The twiddle factors used in the FFT operation are 0, 2, 4,.
..., is shown as 30, these are W ₆₄ ^{0,
_{W 64 2, W 64 4,}} ···, and that of W ₆₄ ^30, the butterfly operation is performed by a method similar to that described above.

G shown in the figure is the calculation of the sixth stage.
The twiddle factors used for the calculation of the IFFT are 0, 1,
2,..., 31 which are W _{64
^{0, W 6 4 1, W}} 64 2, ···, W 64 31 and that of the butterfly operation of this stage is done by the same method as described above for data with each other are spaced 32.

The numbers shown on the right side of the figure indicate the terminals of the output signal in the time domain calculated by this IFFT, and are given here for each carrier frequency supplied in stage 1. A signal obtained by adding and synthesizing the signals of the respective modulated carriers modulated by the modulated signals to be supplied is supplied as an output.

Here, when the fifth stage is performed, which channel number corresponds to which of a to d is determined. Assigning to a and making the remainder zero will result in channel number 0, allocating to b and leaving the remainder to zero will result in channel number 1; allocating to c and leaving the remainder to zero will result in channel number 2; Is zero, channel number 3 is obtained. Channel number 0,
In the case of 1, the block f need not be calculated, and in the case of the channel numbers 2 and 3, the block e need not be calculated.

Therefore, the first stage to the fourth stage are substituted by a 16-point IFFT operation (common to each channel), and in the fifth stage, the former half or the latter half of the 64-point IFFT operation is performed depending on the channel number. Omitting, when performing further calculations, one of the butterfly calculations is calculated as zero, and in the sixth stage, one of the butterfly calculations is calculated as zero according to the channel number, so that every fourth carrier used by each channel is calculated. Thus, an intermittent multicarrier signal can be generated.

Thus, the first type shown in FIG.
In the 64-point IFFT according to the embodiment of the present invention, the modulation signals corresponding to channels 0 to 3 are supplied to the respective input terminals indicated as a to d, and the respective stages 1 to 4
Is performed in accordance with the signal supplied to each channel, and the output terminal of the stage 6 is supplied with time-series data as an output of a signal in which the carrier of each channel is modulated. I have.

In FIG. 15, for channel numbers 0 to 3,
Indicates the number of the carrier used to transmit the information signal supplied thereto. The order of the carriers shown here is the order of the bit reverse.
Are the same numbers as those described in the above.

Next, an IFFT for a multi-channel transmission device
A second embodiment will be described with respect to the calculation method of. FIG.
FIG. 6 shows the configuration of the IFFT. The configuration shown here is
This is an algorithm of frequency-decimation type output data alignment type 64-point inverse discrete Fourier transform, and includes stages 1 to 6. The stages 1 to 4 have four operation blocks of p to s. The operation method in each of these blocks is the same, but the input data supplied, the twiddle factor used for the operation, and the modulation are applied. Carrier numbers are different from one another.

That is, the input signals corresponding to the transmission channels of channels 1 to 4 are supplied to the operation blocks of p to s.
Modulated signal data for carriers having carrier numbers 0, 32, 16,... Are supplied. Channel 2
Are input to the arithmetic block of q for carrier numbers 2, 34, 18,..., Channel 3 has carrier numbers 1, 33, 17,. Are supplied with data for the carrier numbers 3, 35, 19,... Of the operation block of q.

Here, in order to explain the operation of the 64-point IFFT, FIG. 17 shows an 8-point frequency thinning-out type and output data alignment type inverse discrete Fourier transform algorithm, and its operation will be described. In the figure,
X shown on the left

[0], X [4], X [2], X [6] X
[1], X [5], X [3] and X [7] indicate input signals in the frequency domain, and x shown on the right side

[0] to x [7]
Indicates an output signal in the time domain.

In the butterfly operation of this IFFT, the direction of the arrow shown in the figure indicates the direction in which the signal is supplied.
When a constant (twiddle factor, -1) is shown near the arrow, multiply by this constant to provide a signal in the direction of the arrow. Arrows without constants indicate that they are supplied by multiplying by 1, or that they simply supply a signal. At the nodes marked with two arrows facing each other, the signals supplied by those arrows are added.

The twiddle factor shown in FIG.
Is used, which is the radius shown in the complex plane
The eight circles are made to correspond to the positions where the circumference of one circle is divided into eight equal parts.
Number W ₈ ⁰, W₈ ¹, W₈ ^Two, ..., W₈ ⁷Of the value with the value of
In the example of the 8-point IFFT shown here,
Of these eight twiddle factors, W₈ ⁰, W₈ ¹, W₈ ^Two, W₈ ^Threeof
Four are used for calculation.

In the 64-point inverse discrete Fourier transform of the output data alignment type of the time thinning-out type shown in the first embodiment, a, b, c, d in FIG. Perform a common operation. However, in the frequency-decimation type output data alignment type 64-point inverse discrete Fourier transform, p to s in FIG.
Performs no common operation, and each of p, q, r, and s is operated by a different twiddle factor. Here, among these stages, the twiddle factors used in the first stage will be described.

The twiddle factor used in the IFFT of N = 64 points is as shown in FIG. 14, and the twiddle factor W ₆₄ ^k is shown by the number of only k. The twiddle factors at p are 0, 16, 8, 24, 4, 20, 1
The twiddle factors at 2,28 q are 2, 18, 10, 26, 6, 22, 1,
The twiddle factors at 4, 30 r are 1, 17, 9, 25, 5, 21, 1
The twiddle factors at 3,29 s are 3,19,11,27,7,23,1,
5, 31.

A part of the contents shown here will be described in detail. That is, the operation on p is 0, 32, 16, 48,
8, 40, 24, 56, 4, 36, 20, 52, 12,
Calculations for modulating 16 frequencies of numbers 44, 28, and 60 are performed in the first to fourth stages, some of which are illustrated. FIG. 18 shows that the numbers 0, 32, 16,
This figure shows a method of performing calculations from the first to third stages for eight carriers of 48, 8, 40, 24, and 56.

Using the calculation method shown here, each of them is 1
It is easier than described above to extend the operation method to the first stage to the fourth stage of each of p to s in which the IFFT operation is performed on six carriers.

As described above, the butterfly operations of p to s performed in these stages are performed in the same manner, but the twiddle factors used are different. However, if the constants of the twiddle factors are provided in advance in a table and stored in the table, the butterfly operation can be performed while referring to the stored constants. , Easy arithmetic processing can be performed.

For the operation at the front of the IFFT in which the operation methods of the first to fourth stages are the same, a 16-point inverse discrete Fourier transform can be used as in the first embodiment. Only a small amount of computation is required. That is, if the channel number is 0, only p is set;
This is because, if q, only r, if channel number 2, only r, and if channel number 3, only s.

Next, the operation at the rear of the 64-point IFFT will be described. In the fifth stage shown in FIG. 16 described above, there are operation blocks of t and u, but the twiddle factors in these operations are different. That is, operation using the rotation factor W ₆₄ ⁰ in block t, using the rotation factor arithmetic module u in W ₆₄ ^16, performs butterfly operation of the data with each other are disposed 16 apart and in these operation blocks.

[0099] In operation block v sixth stage, performs butterfly operation in 32 separated are data together with the rotation factor W ₆₄ ^0, the calculated result is x

[0] to x [6
3], the time-series data is output from the 64-point IFFT.

Here, when performing the fifth stage, which channel is determined depending on which of the operations p to s is performed. When p is calculated and the remainder is set to zero, the channel number becomes 0. When q is calculated and the remainder is set to zero, the channel number is set to 1. When r is calculated and the remaining is set to zero, the channel number is set to 2. If the remainder is set to zero, the channel number becomes 3. In the case of the channel numbers 0 and 1, the block u does not need to be operated, and the channel numbers 2 and
In the case of 3, it is needless to say that the block t need not be operated.

FIG. 19 shows a method of the frequency thinning-out operation described above. When performing a butterfly operation using the twiddle factor W on the input signals X = Re1 + jIm1 and Y = Re2 + jIm2 expressed by complex numbers in the frequency domain, x = (Re1 + Re2) + j (Im1 + Im2) and y = ((Re1-Re2) + j (Im1-I
m2)) * W is obtained.

Next, the calculation results of the fifth and sixth stages for each channel are shown. Here, as described above, the twiddle factor used for the calculation of the 64-point IFFT is W ₆₄ ⁰ =
1. Since W ₆₄ ¹⁶ = j, the calculation using these is performed by calculating the calculation result of the fourth stage in the Z time series as Z = ｛z1,
When expressed as z2, z3, z4, ..., z15},
The output for each channel number is as follows.

In channel number 0, Z, Z, Z, Z,
That is, ｛z1, z2, ..., z15, z1, z2, ..., z
, Z1, z2, ..., z15, z1, z2, ..., z15}. In channel number 1, Z, -Z, Z, -Z, ie, ｛z1, z2, ..., z15, -z1, -z2, ..., -z1
, Z1, z2, ..., z15, -z1, -z2, ..., -z15}. In channel number 2, Z, jZ, -Z, -j
Z, that is, ｛z1, z2, ..., z15, j * z1, j * z2,
..., j * z15, -z1, -z2, ..., -z15, -j * z1, -j * z
2, ..., -j * z15｝. For channel number 3,
Z, −jZ, −Z, jZ, that is, ｛z1, z2,.
・, Z15, -j * z1, -j * z2, ..., -j * z15, -z1, -z2,
..., -z15, j * z1, j * z2, ..., j * z15}.

Therefore, the first of the 64-point IFFT operation
The stages from the fourth stage to the fourth stage are substituted by 16-point IFFT conversions with different twiddle factors. In the fifth and sixth stages, the omitted 64-point IFFT conversion as described above is performed, and the four channels used by each channel are used. It is possible to generate an intermittent multicarrier signal composed of every other carrier.

Next, an IFFT for a multi-channel transmission device
Will be described together with the third embodiment. FIG.
0 shows the configuration of the IFFT. The configuration shown here is
This is an algorithm of a 64-point inverse discrete Fourier transform of the input data alignment type of the time thinning type, and is composed of stages 1 to 6. In this example, in the first stage, a butterfly operation is performed between data at 32 distances, which is half of the total number of points, and a butterfly operation is performed between data at close positions each time the stage advances.

FIG. 21 shows an algorithm of a 16-point inverse discrete Fourier transform of the input data alignment type of the thinning-out type, and the manner of calculation will be described. In the same figure, the places indicated by black circles are signal connection points, which are connected by diagonal lines, and four black circles located at the vertices of a rectangle are subjected to butterfly computation by two intersecting lines connecting them. Is shown. 0, 1, 2, shown on the left side of FIG.
.., 15 indicate the number of the input signal in the frequency domain, and 0, 8, 4,.
Indicates the number of the output signal in the time domain.

In the figure, the numbers shown at the intersections of the two lines are the twiddle factors used for performing the butterfly operation, and the twiddle factors used for the 16-point IFFT operation shown in FIG. Is used. In the figure, the values of the 16 coefficients W ₁₆ ⁰ , W ₁₆ ¹ , W ₁₆ ² ,..., W ₁₆ ¹⁵ are shown. Here, the values of W ₁₆ ^{0 to} W ₁₆ ⁷ are shown. 8
Are used in the calculation, and these twiddle factors are indicated by numbers 0 to 7. In this manner, the IFFT operation is performed while repeating the butterfly operation. The first stage, the second stage, and the third stage are referred to from the left in units of columns on which the operation is performed, and the 16-point IFFT described here is used. In this case, calculations up to the fourth stage are performed.

Regarding this IFFT calculation, a calculation method using a twiddle factor will be described with reference to an 8-point IFFT. FIG. 22 shows a calculation method for this IFFT. A calculation method of the time thinning type and the input data alignment type 64-point inverse discrete Fourier transform will be described.
In the figure, X shown on the left side

[0] to X [7] indicate input signals in the frequency domain, and x shown on the right side

[0], x
[4], x [2], x [6] x [1], x [5], x
[3] and x [7] indicate output signals in the time domain.

In the butterfly operation of this IFFT, the direction of the arrow shown in the figure indicates the direction in which the signal is supplied.
When a constant (twiddle factor) is shown near the arrow, multiply by this constant and supply the signal in the direction of the arrow. Arrows without constants indicate that they are supplied by multiplying by 1, or that they simply supply a signal. At the nodes marked with two arrows facing each other, the signals supplied by those arrows are added.

The twiddle factor shown in FIG.
Is used, which is the radius shown in the complex plane
The eight circles are made to correspond to the positions where the circumference of one circle is divided into eight equal parts.
Number W ₈ ⁰, W₈ ¹, W₈ ^Two, ..., W₈ ⁷Of the value with the value of
Things.

In this way, the operation of the time decimating type input data alignment type 64-point inverse discrete Fourier transform is performed. The operation of the third embodiment shown here will be described in further detail.

First, when generating a multicarrier to be transmitted with the channel number 0, 0, 4, 8,.
The information to be transmitted is allocated to 60, and the others are set to zero, and the calculations of the first to sixth stages are performed by the 64-point IFFT.

When the channel number is 1, information to be transmitted is allocated to 2, 6, 10,...
The others are set to zero, and the calculations of the first to sixth stages are performed using a 64-point IFFT. In the case of the channel number 2, the information to be transmitted is assigned to 1, 5, 9,..., 61 on the left side, the others are set to zero, and the calculations of the first to sixth stages are performed by the 64-point IFFT. Finally, in the case of the channel number 3, the information to be transmitted is allocated to 3, 7, 11,..., 63 on the left side, and the others are set to zero, and the calculations of the first to sixth stages are performed by 64-point IFFT.

The IFFT operation thus performed is as follows.
As can be seen from the comparison between the 64-point twiddle factor and the 16-point twiddle factor described above, the operations in the first to fourth stages are equivalent to the 16-point inverse discrete Fourier transform shown in FIG. Therefore, 6 shown in FIG.
The calculations of the first to fourth stages of the 4-point IFFT can be performed using this 16-point IFFT instead.

Here, the 64-point I shown in FIG.
In the FFT calculation table, 64 circles are shown between the fourth stage and the fifth stage, and 16 of them are black circles. The black circles indicate the data allocation to the fifth stage when the channel number is 0.

That is, the operations of the first to fourth stages are
When performing the 16-point inverse discrete Fourier transform, 16 data are obtained, and 64 of these 16 data are obtained.
The transmission channel of the data can be determined by the way of assignment to the subsequent stage of the point IFFT.

That is, the assignment of data to channel number 0 is made up of 64 nodes to which signals are supplied to the fifth stage, that is, 0, 1, 2, 3,. , 63, the data is allocated to 0, 4, 8, 12,..., And the channel number 1 is 2, 6, 6 out of the 64 data allocation to the fifth stage. Data is allocated to 10, 14,..., And in channel number 2, out of 64 data allocated to the fifth stage, 1, 5, 9, 13,.
··· Allocate data to channel number 3, out of 64 data allocations to the fifth stage, 3, 7,
Data is allocated to 11, 15,..., And the calculations of the fifth and sixth stages of the 64-point IFFT conversion are performed.

Here, when the input signal is applied to only one of the four channels, in the fifth stage, since 48 of the 64 data become zero, the transmission channel IFFT according to number
The calculation can be omitted.

That is, when transmitting a signal of only one channel, it is sufficient to create 32 data from 16 data, and even in that case, one value of the butterfly operation is zero.

Further, in the calculation of the sixth stage,
As a result of the butterfly operation of the fifth stage, one of the output values is zero.
The 32 data become zero, and the calculation can be omitted even in the sixth stage.

The algorithm of the time decimating 64-point inverse discrete Fourier transform when the data input to the IFFT is aligned has been described above. Next, the frequency decimating IFF when the input data is aligned is described.
T will be described. FIG. 23 shows an arrangement of twiddle factors used in the operation of the frequency-decimated IFFT when the input data is arranged, and the IFF for the multi-channel transmitter is shown.
The method of calculating T will be described together with the fourth embodiment.

The configuration shown here is an algorithm of frequency-thinning-out input data alignment type 64-point inverse discrete Fourier transform, and comprises stages 1 to 6. In the first stage shown in this example, a butterfly operation is performed between 32 pieces of data that are half the total number of points apart from each other, and a butterfly operation is performed between data at close positions each time the stage advances. I have.

FIG. 24 shows an algorithm of a 16-point inverse discrete Fourier transform of the input data alignment type of the frequency decimation type, and the manner of calculation will be described. In the figure,
The points indicated by black circles are connection points of signals, which are connected by diagonal lines, and four black circles located at the vertices of a rectangle indicate that butterfly operation is performed by two intersecting lines connecting them. . 0, 1, 2, shown on the left side of the figure
.., 15 indicate the number of the input signal in the frequency domain, and 0, 8, 4,.
Indicates the number of the output signal in the time domain.

The numbers shown at the intersections of the two lines in the figure indicate the twiddle factors used in performing the butterfly operation, which are used in the 16-point IFFT operation shown in FIG. Is used. In the figure, 16 coefficients W ₁₆ ⁰ , W ₁₆ ¹ , W ₁₆ ² ,.
_Although the value of ₁₆ ¹⁵ is shown, here, W ₁₆
⁰ to _W-16 has been used ⁷ eight of the operation, and displaying these operations factors by the number of 0-7.

In this manner, the IFFT operation is performed while repeating the butterfly operation. When the first stage, the second stage, and the third stage are called from the left in units of columns in which the operation is performed, the above-described 16 is used. In the case of a point IFFT, calculations up to the fourth stage are performed.

Regarding this IFFT calculation, a calculation method using a twiddle factor will be described with reference to an 8-point IFFT. FIG. 25 shows a calculation method for this IFFT.
An operation method of the point inverse discrete Fourier transform will be described. In the figure, X shown on the left side

[0] to X [7] indicate input signals in the frequency domain, and x shown on the right side

[0], x [4], x [2], x [6] x [1], x
[5], x [3] and x [7] indicate output signals in the time domain.

In the butterfly operation of this IFFT, the direction of the arrow shown in the figure indicates the direction in which the signal is supplied.
When a constant (twiddle factor, -1) is shown near the arrow, multiply by this constant to provide a signal in the direction of the arrow. Arrows without constants indicate that they are supplied by multiplying by 1, or that they simply supply a signal. At the nodes marked with two arrows facing each other, the signals supplied by those arrows are added.

The twiddle factor shown in FIG. 10 is used as the twiddle factor shown in FIG. 10. Eight twiddle factors correspond to positions obtained by dividing the circumference of a circle having a radius 1 shown in the complex plane into eight equal parts. coefficient _{^{W 8 0, W 8 1,}} W 8 2, ···, we are using the first of four from among W ₈ ^7.

In this way, the operation of the 64-point inverse discrete Fourier transform of the input data alignment type of the frequency thinning type is performed. The operation of the fourth embodiment shown here will be further described.

First, when generating a multicarrier to be transmitted with the channel number 0, 0, 4, 8,.
The information to be transmitted is allocated to 60, and the others are set to zero, and the calculations of the first to sixth stages are performed by 64-point IFFT.

In the case of channel number 1, information to be transmitted is assigned to 2, 6, 10,...
The others are set to zero, and the calculations of the first to sixth stages are performed using a 64-point IFFT. In the case of the channel number 2, the information to be transmitted is allocated to the left side 1, 5, 9,... Finally, in the case of the channel number 3, the information to be transmitted is allocated to 3, 7, 11,..., 63 on the left side, and the others are set to zero, and the calculations of the first to sixth stages are performed by 64-point IFFT.

The IFFT operation thus performed is as follows:
In the 64-point inverse discrete Fourier transform of the input data alignment type of the time thinning type in the third embodiment described above,
Although the operation algorithm of the fourth stage was common, in the frequency decimating type input data alignment type 64-point inverse discrete Fourier transform according to the fourth embodiment, the rotation of the first to fourth stages performed for each channel was performed. Factors are not common,
Different ones are used for each.

Here, the twiddle factors used in the operation of the first stage will be described below. That is, as for the twiddle factor ^{k represented} as W ₆₄ ^k , the twiddle factors of channel number 0 are 0, 4, 8, 12, 16, 20, 24, 28
And the twiddle factors for channel number 1 are 2, 6, 10,
14, 18, 22, 26, 30, and the twiddle factor of channel number 2 is 1, 5, 9, 13, 17, 21, 25,
29, and the twiddle factor for channel number 3 is 3, 7, 11, 15, 19, 23, 27, 31.

As described above, the calculations at these stages are not commonly performed, but if a twiddle factor table is provided for each channel in advance and the calculation is performed with reference to the table, the calculation process for each channel can be easily performed. Become. In that case, the operations of the first to fourth stages can be performed using the above-described 16-point inverse discrete Fourier transform, and in that case, the amount of calculation can be reduced.

Next, the operation in the fifth stage will be described. The twiddle factor used in this stage is W ₆₄
⁰ = 1 and W ₆₄ ¹⁶ = j. In the fifth stage, a butterfly operation is performed on two data pieces separated from each other, and one constant used for the operation is zero.

Here, when performing the operation of the fifth stage,
Regarding the assignment to the 64 nodes, the channel number of the generated signal is determined depending on which point is assigned. That is, data allocation to channel number 0 is performed by assigning 0, 0 from the top among 64 nodes to which signals are supplied to the fifth stage, as indicated by circles in FIG.
, 63, 0, 4, ...
.., channel number 0 when assigned to the 60th and the remainder is set to zero, channel number 1 when assigned to the 2,6,.
,..., And the rest are made zero, the channel number becomes 2, and the 3, 7,...

The twiddle factor used in the calculation of the sixth stage is W ₆₄ ⁰ = 1. In the sixth stage, the butterfly operation is performed by adjacent data, but one of the operated data is zero, and the operation of that part can be omitted. 64 point IFFT in this way
The operations of the fifth and sixth stages of the conversion are performed, and the operation result is supplied to an output terminal as an IFFT output.

In the above-described embodiment, the case where 64 carrier waves are generated by the 64-point inverse Fourier transform has been described for the sake of simplicity. However, the present invention is not limited to the case where the carrier wave is generated by the 64-point inverse Fourier transform. The present invention is not limited to this.
Using a double oversampling technique, 64 carriers may be generated by a 128-point Fourier transform. Also,
Even in this case, it goes without saying that application to generation of a plurality of carriers of 64 or less is possible.

Further, in the description of this embodiment, the radix-2 I
Although described assuming the FFT algorithm, the present invention provides:
The present invention is not limited to this, and may be a radix 4 or a combination thereof. Of course, the size of the IFFT is not limited, and 1024 points, 809
6 points IFFT or more IFFT
It can be applied to FT operation.

Further, in this description, the configuration of every four channels has been described.
The present invention can be applied to a configuration in which a different number of carriers are defined for each channel even in an eight-channel configuration of every eight channels or a 16-channel configuration of every sixteen channels, and the transmission speed is different.

As described above, according to the first to fourth embodiments, the first half of the IFFT stage for generating orthogonal multicarrier signals arranged at intermittent frequencies uses the IFFT operation with a small number of points. When the IFFT circuit is configured by hardware, the size of the circuit can be reduced. When the IFFT circuit is performed by using a digital signal processor (DSP), the number of processing steps of the operation can be reduced. And can be simplified.

Here, the first embodiment is a simple IFFT for generating orthogonal multicarrier signals arranged at intermittent frequencies in the output data-aligned inverse discrete Fourier transform of the time thinning type. The first half of the IFFT operation can be constituted by an IFFT with a small number of points.

Further, in the second embodiment, in order to generate an orthogonal multicarrier signal arranged at intermittent frequencies in the frequency-decimation type and output data alignment type inverse discrete Fourier transform, the first half stage of the IFFT operation has a number of points. And an IFFT with a small number of IFFTs.

According to the device of the third embodiment, in the input data-aligned inverse discrete Fourier transform of the time thinning type, a simplified method for generating orthogonal multicarrier signals arranged at intermittent frequencies is provided. It describes a typical IFFT configuration, in which the first half stage of the IFFT operation can be configured by an IFFT with a small number of points.

Further, according to the device of the fourth embodiment, in the frequency-decimation type and input data aligned type inverse discrete Fourier transform, an orthogonal multicarrier signal arranged at intermittent frequencies is generated. The first half stage can be constituted by an IFFT having a small number of points.

As described above, the four embodiments which are combinations of the frequency thinning type and the time thinning type, and the input data alignment type and the output data alignment type have been described.
In any case, the first half stage of the IFFT operation can be constituted by an IFFT having a small number of points.
In any of the configurations, it is possible to configure an apparatus that generates an orthogonal multicarrier signal that is intermittent in frequency using an IFFT having a simple configuration.

The first and second stages combined here are of a frequency thinning type and a time thinning type.
It is obvious that, besides using the same combination of the input data alignment type and the output data alignment type, these different combinations can be combined by changing the connection conditions of the connection points.

Here, in each embodiment, the first half stage is changed to a 16-point IFFT for a 64-point IFFT.
4 stages by FT, 64 points of I in the latter half operation
Although the calculation method using the fifth and sixth stages of the FFT has been described, the number of points and the number of stages of the IFFT are not limited to these, and any number may be used. Thus, it is possible to configure a transmission system in which the influence on multipath distortion is further improved.

In the present embodiment, the method of radiating the high-frequency signal generated by the simplified IFFT as a radio wave to the spatial transmission path has been mainly described. However, the multi-carrier generation method described here is described. The transmission of the signal generated by is not limited to this, and may be used for many intermittent orthogonal multi-carrier signal transmission devices such as a method using infrared rays, a method using a coaxial cable, a telephone line, and a method using an optical cable. it can.

[0150]

As described above, according to the present invention, an intermittent orthogonal multicarrier signal composed of every Lth carrier for an integer value L larger than 2 is converted to an M point for an integer value M larger than 2. And an arithmetic stage that performs the inverse discrete Fourier transform of N points for an integer value N greater than twice M, the latter half of an arithmetic stage that performs an inverse discrete Fourier transform of
A digital IC circuit having a smaller circuit size than that of the related art can generate an intermittent orthogonal multicarrier signal with an inexpensive configuration. Digital signal processor (DSP)
And the like, the number of calculation steps can be reduced, and it can be realized with inexpensive functions.

According to the first aspect of the present invention, it is necessary to calculate the first half stage of an orthogonal multicarrier signal intermittent in frequency by an IFFT circuit having a small number of points to generate a final carrier frequency. Since the IFFT calculation stage with a small number of points only needs to be performed in the latter half of the stage, the effect of interference due to multipath distortion generated on the transmission line can be reduced by a simple IFFT, and the spectrum of the modulated signal can be made rectangular to occupy more. It has the advantages of narrowing the bandwidth, generating intermittent quadrature multicarrier signals that can be used efficiently even when the transmission path is degraded in a local frequency domain. .

According to the second aspect of the present invention, when transmitting signals of a plurality of channels using intermittently existing multicarrier signals, the number of points for generating signals of a plurality of channels is particularly high. A small number of IFFT circuits can be added to generate a quadrature multicarrier signal for transmitting signals of a plurality of channels. Therefore, an inexpensive configuration using a small-sized digital IC circuit, and a digital signal processor having a small number of operation steps Accordingly, there is an effect that an intermittent orthogonal multicarrier transmission apparatus capable of transmitting signals of a plurality of channels can be realized at low cost.

According to the third aspect of the present invention, in particular, the orthogonal multicarrier signal to be transmitted using a channel selected in advance among a plurality of transmission channels is rotated by an IFFT circuit having a small number of points. A quadrature multi-carrier signal for transmission on the selected transmission channel can be generated while designating the constants of the factors. Therefore, an inexpensive configuration of a digital IC circuit with a small circuit scale and a digital signal processor with a small number of operation steps There is an effect that an intermittent orthogonal multi-carrier transmission device capable of transmitting a signal of a selected channel can be realized at low cost.

Further, according to the fourth aspect of the present invention, in particular, an orthogonal multicarrier signal for transmitting while designating a plurality of transmission channels is converted to a signal having a small number of points.
Since the transmission channel can be selected by switching the output signal of the FFT circuit to the input node of the latter half stage for performing the IFFT operation, a quadrature multi-carrier signal transmission device having a transmission channel switching function can be implemented by a small-scale digital With an inexpensive configuration of the IC circuit,
Further, there is an effect that the digital signal processor having a small number of operation steps can be realized at low cost.

According to the fifth aspect of the present invention, an orthogonal multicarrier generation method by a simple method is particularly shown, and an orthogonal multicarrier signal generated by this method uses a large number of transmission media. The multi-carrier signal can be transmitted, and the generation of the multi-carrier signal can be realized at low cost by digital signal processing with a smaller number of operation steps.

According to the sixth aspect of the present invention, a method for generating an orthogonal multicarrier signal capable of selecting a transmission channel by a simple method is shown. Is applied to a large number of transmission media, and there is an effect that generation of a transmission channel switching type multicarrier signal can be realized at low cost by digital signal processing with a smaller number of operation steps.

[Brief description of the drawings]

FIG. 1 is a block diagram of an orthogonal multicarrier transmission apparatus according to the present invention.

FIG. 2 is a block diagram of an example of an orthogonal multicarrier signal transmission device to which the generation method of the present invention is applied.

FIG. 3 is a block diagram of an orthogonal multicarrier receiving apparatus that receives a signal of the orthogonal multicarrier transmitting apparatus to which the generation method of the present invention is applied.

FIG. 4 is a frequency spectrum diagram illustrating an example of an orthogonal multicarrier signal generated by the multicarrier transmission apparatus of the present invention.

FIG. 5 is a diagram illustrating a relationship between a channel number of an orthogonal multicarrier signal generated by the multicarrier transmission apparatus of the present invention and a carrier number used.

FIG. 6 is a diagram showing a signal flow diagram of a 4-point IFFT by time thinning.

FIG. 7 is a diagram illustrating a twiddle factor of a 4-point IFFT.

FIG. 8 is a diagram illustrating connection to an IFFT element for generating a multicarrier transmission signal by 16-point IFFT.

FIG. 9 is a signal flow diagram of an output data-aligned 8-point IFFT by time thinning.

FIG. 10 is an explanatory diagram of a twiddle factor used for an 8-point IFFT.

FIG. 11 is a diagram illustrating a calculation of an output data alignment type 16-point IFFT by time thinning.

FIG. 12 is an explanatory diagram of a twiddle factor used for a 16-point IFFT.

FIG. 13 is a diagram for explaining an algorithm of an output data alignment type 64-point inverse discrete Fourier transform to which the generation method of the present invention is applied.

FIG. 14 is an explanatory diagram of a twiddle factor used for a 64-point IFFT.

FIG. 15 is a diagram showing carrier numbers used for channel numbers of orthogonal multicarrier signals generated by the multicarrier transmission apparatus of the present invention in the order of bit reverse.

FIG. 16 is a diagram illustrating an algorithm of output data alignment type 64-point inverse discrete Fourier transform by frequency thinning.

FIG. 17 is a diagram showing an algorithm of an 8-point frequency thinning-out type and output data alignment type inverse discrete Fourier transform.

FIG. 18 is a diagram illustrating an algorithm of a 64-point frequency thinning type, output data aligned type inverse discrete Fourier transform.

FIG. 19 is a diagram illustrating a method of frequency-decimated IFFT calculation.

FIG. 20 is a diagram illustrating an algorithm of a 64-point inverse discrete Fourier transform of the input data alignment type of the time thinning type to which the generation method of the present invention is applied.

FIG. 21 is a diagram illustrating a calculation of an input data alignment type 16-point IFFT by time thinning.

FIG. 22 is a diagram showing a signal flow of an input data alignment type 8-point IFFT by time thinning.

FIG. 23 is a diagram illustrating an algorithm of a 64-point inverse discrete Fourier transform of the input data alignment type of the frequency decimation type to which the generation method of the present invention is applied.

FIG. 24 is a diagram illustrating a calculation of an input data alignment type 16-point IFFT by frequency thinning.

FIG. 25 is a diagram illustrating a signal flow of an 8-point inverse discrete Fourier transform of an input data alignment type of a frequency decimation type.

FIG. 26 is a block diagram of a conventional multicarrier transmission device.

FIG. 27 is a block diagram illustrating an example of a conventional multicarrier signal transmission device.

FIG. 28 is a block diagram of a multicarrier receiving apparatus that receives a signal of a conventional multicarrier transmitting apparatus.

[Explanation of symbols]

Reference Signs List 30 Multicarrier transmission device 34 Multicarrier transmission device 36 Multicarrier reception device 40 Input circuit section 40a to 40d input circuit 41 Information signal input terminal 41a Ch1 input terminal 41b Ch2 input terminal 41c Ch3 input terminal 41d Ch4 input terminal 42 input circuit 42a to 42d input circuit 50 OFDM transmitter 51a-51d first-fourth arithmetic unit (first inverse discrete Fourier arithmetic unit) 52 post-stage arithmetic unit (second inverse discrete Fourier arithmetic unit) 53 output buffer 54 D / A converter 55 Quadrature modulator 56 Signal generator 57 90 ° shifter 58 Frequency converter 59 Transmitter 60 OFDM receiver 61 Receiver 62 Frequency converter 63 Intermediate frequency amplifier 64 Quadrature demodulator 65 Synchronous signal generator 66 90 ° shifter 67 LPF 68 A / D converter 69 Guard inter Bal period processing circuit 70 Decoding circuit 81a to 81d Output circuit 82 Data output terminal 82a to 82d Ch1 to Ch4 output 130 Multicarrier transmission device 134 Multicarrier transmission device 136 Multicarrier reception device 140 Input circuit unit 150 OFDM transmission unit 151 Arithmetic unit 160 OFDM receiving section 170 decoding circuit 180 output circuit section

Claims (6)

[Claims] 1. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on a digital information signal to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path; Used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform complementarily with the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the path, And a quadrature multi-carrier signal transmission device for generating a quadrature multi-carrier signal on the transmission side, wherein the digital information signal to be transmitted is provided, which is responsible for the first half stage of the inverse discrete Fourier transform, and is supplied with an integer value M larger than 2 First inverse discrete Fourier transform means for performing an inverse discrete Fourier transform of M points with respect to The quadrature multi-carrier signal is output by performing N-point inverse Fourier transform on an integer value N larger than twice M for the signal output from the first inverse discrete Fourier transform means, which is responsible for the latter half stage of the Rier transform. A second inverse discrete Fourier transform means, and to supply the orthogonal multicarrier signal output from the second inverse discrete Fourier transform means to the transmission path,
An orthogonal multicarrier signal transmission device, comprising: a high-frequency signal generation unit that converts the orthogonal multicarrier signal into a high-frequency signal. 2. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on digital information signals of a plurality of channels to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path. And a receiving side that reproduces the digital information signals of the plurality of channels by performing a discrete Fourier transform complementarily to the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the transmission path. An orthogonal multicarrier signal transmission device used in a transmission system and generating an orthogonal multicarrier signal on a transmission side, which is responsible for a first half stage of the inverse discrete Fourier transform and supplies a digital signal of a plurality of channels to be transmitted. To perform an M-point inverse discrete Fourier transform on an integer value M greater than 2. Number of first inverse discrete Fourier transform means, and a second half of the inverse discrete Fourier transform, and each of the signals output from the plurality of first inverse discrete Fourier transform means is integrated into an integer greater than twice M. Second inverse discrete Fourier transform means for performing an N-point inverse Fourier transform on a numerical value N to output the orthogonal multicarrier signal; and transmitting the orthogonal multicarrier signal output from the second inverse discrete Fourier transform means to the transmission To supply the road
An orthogonal multicarrier signal transmission device, comprising: a high-frequency signal generation unit that converts the orthogonal multicarrier signal into a high-frequency signal. 3. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on a digital information signal to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path; Used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform complementarily with the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the path, And a quadrature multi-carrier signal transmission device for generating a quadrature multi-carrier signal on a transmission side, which is responsible for the first half stage of the inverse discrete Fourier transform, and is supplied with the digital signal to be transmitted, for an integer value M larger than 2. A first M-point inverse discrete Fourier transform is performed using a twiddle factor corresponding to a desired transmission channel. An inverse discrete Fourier transform means, and a second half of the inverse discrete Fourier transform, and outputs a signal output from the first inverse discrete Fourier transform means to an N-point inverse Fourier for an integer value N larger than twice M. Second inverse discrete Fourier transform means for performing conversion and outputting the orthogonal multicarrier signal, and supplying the orthogonal multicarrier signal output from the second inverse discrete Fourier transform means to the transmission path,
An orthogonal multicarrier signal transmission device, comprising: a high-frequency signal generation unit that converts the orthogonal multicarrier signal into a high-frequency signal. 4. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on a digital information signal to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path; Used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform complementarily with the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the path, And a quadrature multi-carrier signal transmission device for generating a quadrature multi-carrier signal on a transmission side, which is responsible for the first half stage of the inverse discrete Fourier transform, and is supplied with the digital signal to be transmitted, for an integer value M larger than 2. First inverse discrete Fourier transform means for performing an inverse discrete Fourier transform of M points; An input terminal corresponding to a desired transmission channel of an N-point inverse Fourier transform for an integer value N greater than twice M, which is responsible for the latter half of the transform and outputs from the first inverse discrete Fourier transform means. And a second inverse discrete Fourier transform unit for performing an operation to output the orthogonal multicarrier signal, and supplying the orthogonal multicarrier signal output from the second inverse discrete Fourier transform unit to the transmission path. for,
An orthogonal multicarrier signal transmission device, comprising: a high-frequency signal generation unit that converts the orthogonal multicarrier signal into a high-frequency signal. 5. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on a digital information signal to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path; Used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform complementarily with the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the path, And a quadrature multi-carrier signal transmission method for generating a quadrature multi-carrier signal on the transmission side, wherein the digital information signal to be transmitted is provided for the first half stage of the inverse discrete Fourier transform and to be transmitted, and an integer M larger than 2 A first inverse discrete Fourier operation of performing an M-point inverse discrete Fourier transform on The quadrature multi-carrier signal is output by performing an inverse Fourier transform of N points for an integer value N larger than twice M for a signal which is in charge of the latter half stage of the Fourier transform and output from the first inverse discrete Fourier operation step. A second inverse discrete Fourier transform step, and a high frequency converting the orthogonal multicarrier signal into a high frequency signal in order to supply the orthogonal multicarrier signal output from the second inverse discrete Fourier transform step to the transmission path. A signal generation step. 6. A transmitting side for generating an orthogonal multicarrier signal by performing an inverse discrete Fourier transform on a digital information signal to be transmitted, and outputting a transmission signal based on the generated orthogonal multicarrier signal to a transmission path; Used in an information transmission system having a receiving side that reproduces the digital information signal by performing a discrete Fourier transform complementarily with the inverse discrete Fourier transform on the transmitting side of the orthogonal multicarrier signal obtained by demodulating the transmission signal received from the path, And a quadrature multi-carrier signal transmission method for generating a quadrature multi-carrier signal on the transmission side, wherein the digital signal to be transmitted is provided for the first half stage of the inverse discrete Fourier transform, and the digital signal to be transmitted is supplied. A first M-point inverse discrete Fourier transform is performed using a twiddle factor corresponding to a desired transmission channel. An inverse discrete Fourier operation step, and a signal output from the first inverse discrete Fourier transform means, which is in charge of the latter half stage of the inverse discrete Fourier transform, and outputs an N-point inverse Fourier for an integer value N larger than twice M. A second inverse discrete Fourier transform step of performing a transform to output the orthogonal multicarrier signal, and supplying the orthogonal multicarrier signal output from the second inverse discrete Fourier transform step to the transmission path, A high-frequency signal generating step of converting the orthogonal multi-carrier signal into a high-frequency signal.