JP2001136150A - Transmission system for ofdm signal using control signal and device and method relating to the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a transmission efficiency of an OFDM signal with a simple device so as to reduce a data delay time. SOLUTION: A control signal recovery section 141 directly recovers a control signal from a received OFDM signal without applying Fourier transform to the OFDM signal so as to more quickly apply the control signal to each processing section. A Fourier transform section 1 applies Fourier transform to the received OFDM signal. A data demodulation section 3, a de-interleave section 4 and an error correction section 5 respectively demodulate the OFDM signal subjected to Fourier transform by the Fourier transform section 1, de- interleave the demodulated signal, and correct the error to obtain demodulated data according to a modulation system, an interleave size and a kind of error correction designated by the control signal recovered by the control signal recovery section 141 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM signal transmission system using a control signal and an apparatus and method related thereto, and more particularly, to an OFDM signal transmission method that transmits an OFDM symbol corresponding to a control signal to thereby correct an error correction. The present invention relates to an OFDM signal transmission system that specifies transmission parameters such as a type, an interleave size, and a modulation method, and an apparatus and method related thereto.

[0002]

2. Description of the Related Art Generally, in a wireless or wired transmission system, transmission parameters such as data encoding and modulation methods are sometimes changed depending on the importance of data to be transmitted and the state of a transmission path. In this case, since both the transmission side and the reception side need to perform data processing corresponding to the transmission parameter, when changing the transmission parameter, both the transmission side and the reception side obtain information about the transmission parameter in advance. Need to be kept.

Conventionally, as a method of changing a transmission parameter, there has been a method in which information on a transmission parameter to be changed is transmitted as a control signal from a transmission side, so that information on the transmission parameter is transmitted to a reception side in advance. In orthogonal frequency division multiplexing (hereinafter, referred to as OFDM) transmission, transmission parameters could be changed in the same manner.

[0004] Here, OFDM transmission is a method of transmitting information by placing data to be transmitted on each of a large number of orthogonal subcarriers and then multiplexing all the subcarriers. It has the advantage of reducing intersymbol interference. QPSK, multi-level QAM, or the like is used as a modulation scheme for each subcarrier.

FIG. 10 is a block diagram showing a configuration of a conventional OFDM signal demodulator capable of designating a transmission parameter using a control signal. In FIG. 10, the conventional OFDM
The signal demodulation device includes a Fourier transform unit 1, a data demodulation unit 3,
It includes a deinterleave unit 4, an error correction unit 5, and a control signal demodulation unit 102. Hereinafter, the operation of the demodulation device will be described.

In FIG. 10, a received signal multiplexed in the order of a preamble, a control symbol, and a data symbol is input to a demodulation device. This reception signal is composed of two-series data of I-axis data and Q-axis data separated by receiving the OFDM signal transmitted from the transmission side at the reception side, converting it into an IF signal, and performing quadrature detection. . Although not shown, the demodulation device is further supplied with a symbol synchronization signal and a clock signal generated from the reception signal itself by the reception-side timing signal generation unit. Each processing unit of the demodulation device performs data processing based on the symbol synchronization signal and the clock signal.

In FIG. 10, the input control symbols and data symbols are OFDM symbols generated by carrying out an inverse Fourier transform after placing different data for each subcarrier constituting each symbol. In order to obtain the information carried on each of the subcarriers, it is necessary to perform a Fourier transform on those symbols.

[0008] The Fourier transform unit 1 performs a Fourier transform of the received signal and supplies the Fourier transform to the control signal demodulation unit 102 and the data demodulation unit 3. The control signal demodulation unit 102 is a Fourier transform unit 1
The demodulation process is performed on the control symbol portion in the Fourier transform output of, and a control signal is reproduced, and supplied to the data demodulation unit 3, the deinterleave unit 4, and the error correction unit 5.

A data demodulation unit 3, a deinterleave unit 4 and an error correction unit 5 perform demodulation processing on a data symbol portion in a Fourier transform output of the Fourier transform unit 1 based on a transmission parameter indicated by the control signal. Deinterleave processing and error correction processing are performed, and demodulated data is output.

[0010]

As described above, in the conventional OFDM signal transmission system, the control signal is supplied to each processing unit after the data demodulation unit 3 because the control symbol is Fourier-transformed. And after demodulation by the control signal demodulation unit 102. On the other hand, the data symbol is supplied to the data demodulation unit immediately after the data symbol is subjected to the Fourier transform.

Here, since a control signal is required for data processing after the data demodulation unit 3, the control signal needs to be supplied to each processing unit after the data demodulation unit 3 before the data symbol. is there. However, if a data symbol is received immediately after the control symbol, the data symbol is input to the data demodulation unit 3 first while the control signal is being demodulated by the control signal demodulation unit 102. It cannot be demodulated.

Therefore, the data symbol is transmitted to the data demodulation unit 3
Must be delayed by the time required for demodulation of control symbols, and the following two methods have been used for that purpose. The first method is to provide a space for the control signal demodulation time between the control symbol and the data symbol of the OFDM signal to be transmitted. The second method is to provide a buffer memory before the data demodulation unit 3 and
By temporarily storing the data symbols, the data demodulation unit 3
This is a method of delaying the input of data symbols to the control signal by the above-described control signal demodulation time.

However, the former has a problem that the transmission efficiency is reduced, and the latter has a problem that an extra storage device is required. Furthermore, since the former delays the data symbol transmission start time and the latter delays the data symbol demodulation start time, the time from the modulation of the transmission data portion on the transmission side to the demodulation on the reception side is the same. And the data delay time increases.

Therefore, it is an object of the present invention to improve transmission efficiency and not require extra storage, and
As a result, OFDM with reduced data delay time
It is an object of the present invention to provide a signal transmission system and an apparatus and method related thereto.

[0015]

A first aspect of the present invention is a system for transmitting an OFDM signal from a transmitting device to a receiving device, the transmitting device comprising: an OFDM symbol corresponding to transmission data; A modulation unit for generating an OFDM signal in which an OFDM symbol corresponding to a control signal for designating a transmission parameter is multiplexed on a time axis; and a transmission unit for transmitting the OFDM signal generated in the modulation unit to a receiving device. , The modulator generates an OFDM symbol corresponding to the control signal by simultaneously modulating all subcarriers with the same phase and amplitude, and the receiving device includes a receiving unit that receives an OFDM signal transmitted by the transmitting device. And a demodulator for demodulating the OFDM signal received by the receiver, wherein the demodulator performs a Fourier transform from the OFDM signal received by the receiver. A control signal reproducing unit for directly reproducing the control signal, and transmission data for reproducing transmission data from the OFDM signal received by the receiving unit based on the control signal reproduced by the control signal reproducing unit by a process including Fourier transform. And a demodulation unit.

As described above, according to the first aspect, the control signal can be directly reproduced from the received signal without performing the Fourier transform on the receiving side. Then, the control signal can be supplied to each data processing unit on the receiving side earlier than the transmission data portion of the reception signal, and demodulation can be performed without delaying the transmission data portion. Therefore, the transmission efficiency can be improved, and no extra storage device is required, and as a result, the data delay time can be reduced.

In a second aspect based on the first aspect, the transmission parameter specified by the control signal is at least one of a modulation scheme, an interleave size, and an error correction type.
Include parameters to specify one.

As described above, according to the second invention, the control signal is transmitted from the transmitting side to the receiving side, in particular, by the modulation method,
Even when at least one of the interleave size and the type of error correction is specified, the effect of the first invention can be obtained.

A third aspect of the present invention is an OFDM signal modulator for generating an OFDM signal including transmission data and a control signal, wherein each subcarrier constituting an OFDM symbol is modulated based on the transmission data. Transmission data modulating means for generating a transmission data modulation signal;
Control signal modulating means for generating a control signal modulation signal by simultaneously modulating all subcarriers constituting an FDM symbol with the same phase and amplitude based on the control signal, and a transmission data modulation signal and a control signal modulation signal And an OFDM signal generating means for generating an OFDM signal in which a transmission data portion including transmission data and a control signal portion including a control signal are multiplexed on a time axis based on the above.

As described above, according to the third aspect, the OF can directly reproduce the control signal without performing the Fourier transform.
The DM symbol can be multiplexed on the transmission data portion. By using the OFDM signal generated in this way, it is possible to transmit to the receiving side without providing a space between the control signal portion and the data signal portion. Therefore,
It is possible to improve the transmission efficiency and reduce the data delay time.

A fourth invention is an OFDM signal demodulator for demodulating a received OFDM signal and reproducing transmission data, wherein the control signal reproduces a control signal directly from the OFDM signal without performing a Fourier transform. The OFDM is performed based on the transmission parameter indicated by the control signal reproduced by the control signal reproducing means by the processing including the reproducing means and the Fourier transform.
Transmission data reproducing means for reproducing transmission data from the signal.

As described above, according to the fourth aspect, the control signal is reproduced from the received OFDM signal without performing the Fourier transform, whereby the control signal is reproduced faster than the transmission data portion of the received signal. Then, the data can be supplied to each data processing means. Then, even when the transmission data portion is received immediately after the control signal portion, demodulation can be performed without delaying the transmission data portion. Therefore,
An extra storage device is not required, and the data delay time can be reduced.

In a fifth aspect based on the fourth aspect, the control signal reproducing means is configured to calculate a correlation value between the OFDM symbol corresponding to the control signal included in the received OFDM signal and a previously prepared time-domain reference signal. It includes a correlating means to be obtained and a judging means for reproducing a control signal by judging the phase and amplitude indicated by the correlation value obtained by the correlating means.

As described above, according to the fifth aspect, in particular, by performing a known correlation operation, the received OF
The control signal can be directly reproduced from the DM signal without performing the Fourier transform processing, and the effect of the fourth invention can be obtained.

In a sixth aspect based on the fourth aspect, the transmission data reproducing means is a Fourier transform means for performing a Fourier transform on the received OFDM signal, a data demodulating means for demodulating an output of the Fourier transform means, and a data demodulating means. And an error correcting means for error correcting the output of the deinterleaving means.

As described above, according to the sixth aspect of the present invention, transmission data is demodulated, deinterleaved, and error-corrected in accordance with the modulation scheme, interleave size, and type of error correction indicated by the control signal transmitted from the transmission side. Even in the case of correction, the effect of the fourth invention can be obtained.

[0027] A seventh invention is an OFDM signal transmitting apparatus for transmitting an OFDM signal containing transmission data and a control signal, wherein each subcarrier constituting an OFDM symbol is modulated based on the transmission data. Transmission data modulating means for generating a transmission data modulation signal;
Control signal modulating means for generating a control signal modulation signal by simultaneously modulating all subcarriers constituting an FDM symbol with the same phase and amplitude based on the control signal, and a transmission data modulation signal and a control signal modulation signal And an OFDM signal generating means for generating an OFDM signal in which a transmission data part including transmission data and a control signal part including a control signal are multiplexed on a time axis, and an OFDM signal generated by the OFDM signal generation means. Transmission means for transmitting.

As described above, according to the seventh aspect, the OF can directly reproduce the control signal without performing the Fourier transform.
The DM symbol can be multiplexed with the transmission data portion and transmitted, and can be transmitted to the receiving side without providing a space between the control signal portion and the data signal portion. Therefore, it is possible to improve the transmission efficiency and shorten the data delay time.

An eighth invention is an OFDM signal receiving apparatus which receives an OFDM signal and reproduces transmission data.
The receiving means for receiving the FDM signal, the control signal reproducing means for directly reproducing the control signal from the OFDM signal received by the receiving means without performing the Fourier transform, and the control signal reproducing means by the processing including the Fourier transform, Transmission data reproducing means for reproducing transmission data from the OFDM signal received by the receiving means based on the transmission parameter indicated by the reproduced control signal.

As described above, according to the eighth aspect, OF OF
Receiving the DM signal and reproducing the control signal from the received OFDM signal without performing Fourier transform, thereby reproducing the control signal faster than the transmission data portion of the received signal and supplying the control signal to each data processing means. Becomes possible. Then, even when the transmission data portion is received immediately after the control signal portion, demodulation can be performed without delaying the transmission data portion. Therefore, an extra storage device is not required, and the data delay time can be reduced.

In a ninth aspect based on the eighth aspect, the control signal regenerating means includes a control signal reproducing means for generating an OFDM symbol corresponding to a control signal included in the OFDM signal received by the receiving means and a time-domain reference signal prepared in advance. Correlation means for determining a correlation value, and determination means for reproducing a control signal by determining the phase and amplitude indicated by the correlation value determined by the correlation means.

In a tenth aspect based on the eighth aspect, the transmission data reproducing means includes a Fourier transform means for performing a Fourier transform on the OFDM signal received by the receiving means, a data demodulating means for demodulating an output of the Fourier transform means, Deinterleaving means for deinterleaving the output of the data demodulation means;
Error correcting means for correcting the output of the deinterleaving means.

An eleventh invention is an OFDM signal modulation method for generating an OFDM signal including transmission data and a control signal, wherein each subcarrier constituting an OFDM symbol is modulated based on the transmission data. ,
Generating a transmission data modulation signal, and simultaneously modulating all subcarriers constituting the OFDM symbol with the same phase and amplitude based on the control signal,
Generating a control signal modulation signal; and an OFDM signal in which a transmission data portion including transmission data and a control signal portion including a control signal are multiplexed on a time axis based on the transmission data modulation signal and the control signal modulation signal. And generating.

A twelfth invention is an OFDM signal demodulation method for demodulating a received OFDM signal and reproducing transmission data, and reproducing a control signal directly from the received OFDM signal without performing a Fourier transform. And a step of reproducing transmission data from the OFDM signal based on a transmission parameter indicated by the control signal by a process including a Fourier transform.

According to a thirteenth aspect, in the twelfth aspect,
The step of reproducing the control signal includes a step of obtaining a correlation value between an OFDM symbol corresponding to the control signal included in the received OFDM signal and a time-domain reference signal prepared in advance, and determining a phase and an amplitude indicated by the correlation value. And reproducing the control signal.

According to a fourteenth aspect, in the twelfth aspect,
Regenerating the transmission data includes performing a Fourier transform on the received OFDM signal, demodulating a result of the Fourier transform, deinterleaving the demodulated result, and correcting an error in the deinterleaved result. Including.

A fifteenth invention is an OFDM signal transmission method for transmitting an OFDM signal including transmission data and a control signal, wherein each subcarrier constituting an OFDM symbol is modulated based on the transmission data. ,
Generating a transmission data modulation signal, and simultaneously modulating all subcarriers constituting the OFDM symbol with the same phase and amplitude based on the control signal,
Generating a control signal modulation signal; and, based on the transmission data modulation signal and the control signal modulation signal, an OFDM signal in which a transmission data portion including transmission data and a control signal portion including a control signal are multiplexed on a time axis. Generating and transmitting an OFDM signal.

A sixteenth invention is an OFDM signal receiving method for receiving an OFDM signal and reproducing transmission data,
Receiving an OFDM signal, regenerating a control signal directly from the OFDM signal without performing a Fourier transform, and processing including a Fourier transform.
Reproducing the transmission data from the OFDM signal based on the transmission parameter indicated by the control signal.

According to a seventeenth aspect, in the sixteenth aspect,
The step of reproducing the control signal includes a step of obtaining a correlation value between an OFDM symbol corresponding to the control signal included in the OFDM signal and a time-domain reference signal prepared in advance.
Reproducing the control signal by determining the phase and the amplitude indicated by the correlation value.

According to an eighteenth aspect, in the sixteenth aspect,
The step of reproducing the transmission data includes a step of performing a Fourier transform on the OFDM signal, a step of demodulating a result of the Fourier transform, a step of deinterleaving the demodulated result, and a step of correcting an error of the deinterleaved result.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of an OFDM signal transmission system using a control signal and a modulation / demodulation device thereof according to the present invention will be described.

FIG. 1 shows an OFD according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of an M signal transmission system.
In FIG. 1, the transmission system includes a transmitting device 9 and a receiving device 10. The transmitting device 9 includes a modulating unit 11 and a transmitting unit 12, and the receiving device 10 includes a receiving unit 13 and a demodulating unit 14. ing. The demodulation unit 14 includes a control signal reproduction unit 141 and a transmission data demodulation unit 142.

Hereinafter, the operation of the transmission system will be described with reference to FIG. In the transmission device 9, the modulation unit 1
1 is supplied with transmission data and a control signal, and outputs a transmission signal obtained by multiplexing OFDM symbols corresponding to these two signals on the time axis. The transmitting unit 12 includes the modulating unit 11
Is converted into a high-frequency OFDM signal and transmitted to the receiving apparatus 10.

In the receiving device 10, the receiving unit 13 receives the OFDM signal transmitted by the transmitting device 9 and outputs a received signal. The control signal reproducing unit 141 reproduces a control signal from the received signal received by the receiving unit 13. The transmission data demodulation unit 142 reproduces transmission data from the reception signal received by the reception unit based on the control signal reproduced by the control signal reproduction unit 141.

FIG. 2 shows an OFD according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of a configuration of an OFDM signal transmitted from a transmission side to a reception side in a transmission system for M signals. In FIG. 2, a preamble 21, a control symbol 22, and finally a data symbol 23 are transmitted from the transmitting side to the receiving side.

Preamble 21 includes a reference signal necessary for estimating the timing, frequency and phase of control symbol 22 and data symbol 23 during demodulation. The control symbol 22 corresponds to a control signal corresponding to a control signal for designating transmission parameters such as a modulation scheme, an interleave size, and an error correction type necessary for demodulating the data symbol 23.
An FDM symbol. Data symbol 23 is an OFDM symbol corresponding to transmission data.

As described later, data symbol 2
In each of the subcarriers forming the control symbol 22, the same control signal is redundantly carried, while the transmission data is dispersed and carried on each of the subcarriers constituting the control symbol 22.

FIG. 3 shows an OFD according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a modulation device provided on a transmission side in an M signal transmission system. In FIG.
The modulation device includes a control signal modulator 31, a switch 32, an error correction encoder 33, an interleaver 34, a data modulator 35, and an inverse Fourier transformer 36.

A control signal and transmission data are input to this modulation device. The control signal is a signal for controlling each processing unit on the transmission side and the reception side according to the transmission parameters optimized as necessary, and includes a control signal modulation unit 31, an error correction coding unit 33, an interleave unit 34, and a data The signal is supplied to the modulation unit 35. Then, the transmission data is supplied to the error correction encoding unit 33. Although illustration is omitted,
This modulator is further supplied with a symbol synchronization signal and a clock signal generated by a timing signal generator on the transmission side. Each processing unit of the modulation device performs data processing based on the symbol synchronization signal and the clock signal.

The control signal modulator 31 divides the control signal into bit strings in a predetermined number of bits, and converts the divided bit strings into complex numbers indicating the positions of the bits on the complex plane. Further, all subcarriers are simultaneously modulated by a complex number corresponding to the control signal.

The error correction coding unit 33 performs error correction coding on the transmission data according to the type of error correction indicated by the control signal. The interleaver 34 interleaves the coded output of the error correction coder 33 according to the interleave size indicated by the control signal.

The data modulating section 35 divides the interleaved output of the interleaving section 34 into bit strings of a predetermined number of bits in accordance with the modulation scheme indicated by the control signal, and divides the divided bit strings into a sequence of the bits on a corresponding complex plane. Each is converted to a complex number indicating the position. Further, each subcarrier is separately modulated by a complex number corresponding to the transmission data.

The switch 32 is connected to the control signal modulator 31 first.
, And then the modulation output from the data modulator 35. The inverse Fourier transform unit 36 outputs a transmission signal by performing an inverse Fourier transform on the modulation output selected by the switch 32.

The transmission signal output from this modulator is a complex number and is composed of two series of data, I-axis data and Q-axis data. After that, the two series of data are quadrature-modulated by the transmitting unit 12 shown in FIG. 1, converted into an IF signal, further converted into an RF frequency, and transmitted to the receiving side.

Next, referring to FIG.
To the inverse Fourier transform unit 36 will be described in more detail. However, in FIG. 4, it is assumed that the switch 32 selects the modulation output from the data modulation unit 35, and the illustration is omitted.

In FIG. 4, the data modulation section 35 includes a complex conversion section 41, a serial / parallel section 42, and a multiplication section 43, and the multiplication section 43 includes multipliers 431 to 43N. The complex converter 41 includes an interleaver 3 based on transmission data.
4 are converted into a complex sequence according to the modulation scheme indicated by the control signal. The serial / parallel unit 42
The complex numbers output from the complex converter 41 are grouped for each number of subcarriers, and are output in parallel to each subcarrier. Each of the multipliers 431 to 43N multiplies a reference complex number of a subcarrier prepared in advance by a complex number output from a serial / parallel unit corresponding to the subcarrier, thereby corresponding to each subcarrier after modulation. Generate a complex number. A predetermined frequency is assigned to each subcarrier. The inverse Fourier transform unit 36 represents a signal in the time domain by performing an inverse Fourier transform on a complex number corresponding to each modulated subcarrier output from the multiplication unit 43 as a value at a frequency assigned to each subcarrier. Generate a complex number.

That is, the processing of the signal corresponding to the transmission data shown in FIG. 4 is the same as the conventional processing of generating a normal OFDM signal.

To summarize the processing in FIG. 4, by modulating the phase and amplitude of each subcarrier in advance with the phase and amplitude corresponding to the transmission data, the modulated phase and amplitude of each subcarrier can be adjusted. I get it. Each subcarrier is arranged on the frequency axis, and the phase and amplitude after modulation of each subcarrier are subjected to inverse Fourier transform to obtain the phase and amplitude of a signal that changes in the time domain.

In the actual processing, the phase and the amplitude are represented by a complex number indicating a position corresponding to the phase and the amplitude on a complex plane, and the modulation processing corresponds to multiplication of the complex numbers. That is, the above-described processing corresponds to obtaining a time-domain complex number by performing an inverse Fourier transform on a result obtained by multiplying the reference complex number of each subcarrier by a complex number corresponding to transmission data.

Next, referring to FIG.
The processing from 1 to the inverse Fourier transform unit 36 will be described in more detail. However, in FIG. 5, it is assumed that the switch 32 selects the modulation output from the control signal modulation unit 31.
Illustration is omitted.

In FIG. 5, the control signal modulation section 31 includes a complex conversion section 51 and a multiplication section 53.
3 comprises multipliers 531 to 53N. Complex converter 51
Converts the control signal into a complex sequence. Multiplier 53
The same complex number converted by the complex converter 51 is input to each of the multipliers 531 to 53N.
Generates a complex number corresponding to each subcarrier after modulation by multiplying the complex number by a reference complex number of each subcarrier prepared in advance. Note that these reference complex numbers may be the same as or different from the reference complex numbers used in the data modulation unit 35. A predetermined frequency is assigned to each subcarrier. The inverse Fourier transform unit 36 represents a signal in the time domain by performing an inverse Fourier transform on the complex number corresponding to each modulated subcarrier output from the multiplication unit 53 as a value at a frequency assigned to each subcarrier. Generate a complex number.

Next, the characteristics of the signal in the time domain output from the inverse Fourier transform unit 36 in FIG. 5 will be described with reference to FIG. First, as shown in FIG.
In FIG. 5, when 1 is input to each of the multipliers 531 to 53N as a complex number corresponding to a control signal, the time domain signal h (t) output from the inverse Fourier transform unit 36 is referred to as a time domain reference signal. I do.

Then, as shown in FIG. 6 (b), k is used as a complex number corresponding to the control signal in FIG.
When input is made to 1 to 53N, each value on the frequency axis input to the inverse Fourier transform unit 36 becomes k times as large as that in the case of FIG. Here, since the inverse Fourier transform is a linear operation, if the entire input value is multiplied by k, the entire output value is also multiplied by k. Therefore, when the complex number corresponding to the control signal is k, the time-domain signal g (t) output from the inverse Fourier transform unit 36 is a signal obtained by multiplying the time-domain reference signal h (t) by k · h (t).

FIG. 7 shows an OFD according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a demodulation device provided on a receiving side in a transmission system for M signals. 7 includes a Fourier transform unit 1, a control signal reproducing unit 141, a data demodulating unit 3, a deinterleaving unit 4, and an error correcting unit 5.
It has.

It should be noted that the OFDM signal demodulation device shown in FIG.
10 is different from that of the OFDM signal demodulator of FIG.
7 reproduces the control signal after the Fourier transform of the received signal, whereas the control signal demodulator 102 shown in FIG.
The only point 41 is to reproduce the control signal without passing the received signal through the Fourier transform. Therefore, with the configuration in FIG.
Components corresponding to those in FIG. 10 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 7, a received signal is input to the demodulation device. The input received signal is obtained by converting the OFDM signal transmitted from the transmitting side into an IF signal in the receiving unit 13 shown in FIG. 1 and then separating the OFDM signal by quadrature detection. It consists of two series of axis data.

Although not shown, the symbol synchronization signal and the clock signal generated from the reception signal itself by the reception-side timing signal generation unit are further supplied to the demodulation device. Each processing unit of the demodulation device performs data processing based on the symbol synchronization signal and the clock signal.

In FIG. 7, first, control symbols are input to the demodulation device, and immediately after that, data symbols are input. The control signal reproducing section 141 reproduces a control signal from a control symbol portion of the received signal by a process described later.
The Fourier transform unit 1 performs a Fourier transform on a data symbol portion of the received signal. The data demodulation unit 3 demodulates the converted output of the Fourier transform unit 1 according to the modulation scheme indicated by the control signal reproduced by the control signal reproduction unit 141. The deinterleaver 4 deinterleaves the demodulated output of the data demodulator 3 according to the interleave size indicated by the control signal reproduced by the control signal reproducer 141. Error correction unit 5
Performs error correction on the deinterleave output of the deinterleaver 4 according to the type of error correction indicated by the control signal reproduced by the control signal reproducer 141, and outputs demodulated data.

Next, the control signal reproducing unit 141 shown in FIG.
Will be described in more detail. FIG. 8 is a block diagram showing a configuration of the control signal reproducing unit 141 in FIG. 7, and the processing of the control signal reproducing unit 141 will be described below with reference to FIG.

The control signal reproducing section 141 includes a correlation section 81 and a judgment section 82. First, a received signal is input to the control signal reproducing unit 141. Correlation section 81 calculates a correlation value between each control symbol of the received signal and the time-domain reference signal based on the symbol synchronization signal by a correlation operation. The determination section 82 determines the correlation value obtained by the correlation section 81 and reproduces a control signal.

Here, the time domain reference signal is shown in FIG.
As described in FIG. 5, the multipliers 531 to 53N in FIG.
, A time domain signal h output from the inverse Fourier transform unit 36 when 1 is input as a complex number corresponding to the control signal
(T), which is represented by a complex number in the time domain. This time domain reference signal is prepared in advance,
It is provided to the correlation unit 81. On the other hand, the control symbol g (t)
FIG. 6 shows a case where a complex number corresponding to a control signal is k.
As described in (b), due to the linearity of the inverse Fourier transform, a signal k · h (t) obtained by multiplying the time-domain reference signal h (t) by k is obtained.

The correlation section 81 obtains a correlation value of the two complex numbers by a correlation operation. More specifically, in the correlation operation, a complex number indicated by a received signal corresponding to a control signal is multiplied by a complex number conjugated to a complex number indicated by a time domain reference signal, and the value is integrated every symbol period. It is done by doing. Due to the above-described characteristic of the received signal corresponding to the control signal, a result of this operation is a complex number proportional to the complex number k carried on the control symbol. The correlation processing in the correlation section 81 is known, and is realized by a multiplier, an integration circuit, and the like.

Based on the complex number obtained by correlation section 81, determination section 82 determines a range including the complex number on a complex plane, converts the complex number into a bit string corresponding to the determined range, and outputs the bit string. I do. This output bit string is the reproduced control signal.

Here, an actual processing method of a signal represented by a complex number, which has been described in the above description, will be described. A signal represented by a complex number is transmitted by being divided into a component corresponding to a real part of a complex number and a component corresponding to an imaginary part of a complex number. For example, the multipliers 431 to 43N or the multipliers 531 to 53N in FIG. 4 or FIG. 5 include a real part and an imaginary part of a complex number corresponding to transmission data or a control signal, and a real part of a reference complex number corresponding to each subcarrier. And the imaginary part are respectively input as a pair, multiplication between the complex numbers is performed, and the resulting complex number is also output as a pair with the respective real and imaginary parts.

Hereinafter, with reference to FIG. 9, the difference in the temporal flow between the demodulation processing of the conventional OFDM signal transmission system according to the model case and the demodulation processing of the OFDM signal transmission system of the present invention will be described. 9 (a) to 9 (b) show a temporal flow of demodulation processing in a conventional OFDM signal transmission system, and FIGS. 9 (e) to 9 (h) show an OFDM signal of the present invention. 5 shows a temporal flow of demodulation processing of a transmission system.

The received signal includes a preamble having a length of 2 symbols and a control symbol 1 having a length of 1 symbol corresponding to the control signal.
It is assumed that the data symbol is composed of data symbols and four data symbols of one symbol length corresponding to data 1 to 4. The processing delay time in the Fourier transform is two symbols long.

Conventionally, the control signal is demodulated after the Fourier transform unit outputs the control symbol, and the data symbol must be supplied to the data demodulation unit after the demodulation of the control signal is completed. That is, it is necessary to supply data symbols at the timing shown in FIG.
As shown in (4), in the Fourier transform output, it is necessary to provide an interval corresponding to the processing time required for demodulating the control signal between the output of the control symbol and the output of the data symbol. Assuming that the data length corresponding to the demodulation processing time of the control signal is 0.5 symbol length, a blank of 0.5 symbol length corresponding to about 7% of the received signal having a total length of 7 symbols is shown in FIG.
It was necessary to provide as shown in (a).

In the present invention, immediately after receiving the control signal, the control signal is reproduced as shown in FIG. Since the processing includes calculation of a correlation value, the processing time is longer than that of the related art, and is set to one symbol length. FIG. 9F shows the Fourier transform output. The first output of the data symbol is output after the demodulation of the control signal is completed. Since this may be directly input to the data demodulation processing, there is no need to provide a blank in the received signal as in the related art.

As described above, according to this model case, the transmission efficiency of the OFDM signal transmission system of the present invention is improved by about 7% as compared with the conventional OFDM signal transmission system, and the transmission and demodulation of the data part are also 0%. .5 symbol length earlier.

Note that the control symbol in the present invention is O
Since the same information is carried on all the subcarriers constituting the FDM signal, the amount of information that can be transmitted is smaller than when different information is carried on each subcarrier. Compared to conventional control signals, since only a part of subcarriers is used in the past, or the same information is carried redundantly with multiple subcarriers in order to reliably transmit control signals. Has little effect on the amount of information. Rather, the control symbol of the present invention can demodulate a control signal even when information of some frequencies is lost due to transmission, and thus is suitable for reliably transmitting important information called a control signal.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an OFDM signal transmission system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an OFDM signal transmission system according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a configuration of a DM signal.

FIG. 3 is a block diagram illustrating a configuration of a modulation device provided on a transmission side in an OFDM signal transmission system according to an embodiment of the present invention.

4 is a block diagram showing a part of the configuration of the modulation device shown in FIG. 3 in more detail.

5 is a block diagram showing a part of the configuration of the modulation device shown in FIG. 3 in more detail.

FIG. 6 is a diagram illustrating an OFDM signal transmission system according to an embodiment of the present invention.
Of the OFDM signals transmitted from the transmitting side to the receiving side,
FIG. 3 is a diagram for explaining characteristics of an OFDM signal corresponding to a control signal.

FIG. 7 is a block diagram showing a configuration of a demodulation device provided on the receiving side in the OFDM signal transmission system according to one embodiment of the present invention.

8 is a block diagram showing a part of the configuration of the demodulation device shown in FIG. 7 in more detail.

FIG. 9 is a diagram showing a temporal flow difference between a demodulation process in a conventional OFDM signal transmission system and a demodulation process in an OFDM signal transmission system of the present invention, according to a model case.

FIG. 10 is a block diagram showing a configuration of a conventional OFDM signal demodulation device capable of designating a transmission parameter using a control signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fourier transformation part 3 ... Data demodulation part 4 ... Deinterleave part 5 ... Error correction part 9 ... Transmission device 10 ... Reception device 11 ... Modulation part 12 ... Transmission part 13 ... Reception part 14 ... Demodulation part 141 ... Control signal reproduction part 142 transmission data demodulation unit 21 preamble 22 control symbol 23 data symbol 31 control signal modulation unit 32 switch 33 error correction encoding unit 34 interleave unit 35 data modulation unit 36 inverse Fourier transform unit 41 Complex conversion unit 42 Serial-parallel unit 43 Multiplication unit 431 to 43N Multiplier 51 Complex conversion unit 53 Multiplication unit 531 to 53N Multiplier 81 Correlation unit 82 Determination unit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hideki Nakahara 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasuo Harada 1006 Kazuma Kadoma, Kazuma, Osaka Matsushita Electric Industrial Co., Ltd.F-term (reference) 5K014 AA01 BA05 FA11 FA16 HA05 HA10 5K022 DD01 DD13 DD17 DD19 DD33

Claims (18)

[Claims] 1. An OFDM transmission method from a transmitting apparatus to a receiving apparatus.
A system for transmitting a signal, wherein the transmitting apparatus generates an OFDM signal in which an OFDM symbol corresponding to transmission data and an OFDM symbol corresponding to a control signal for designating a transmission parameter are multiplexed on a time axis. A modulating unit, and a transmitting unit that transmits an OFDM signal generated in the modulating unit to the receiving device, wherein the modulating unit modulates all subcarriers at the same time with the same phase and amplitude to perform the control. A receiving unit that generates an OFDM symbol corresponding to a signal; a receiving unit that receives an OFDM signal transmitted by the transmitting device; and a demodulation unit that demodulates the OFDM signal received by the receiving unit. A control signal reproducing unit that directly reproduces the control signal from the OFDM signal received by the receiving unit without performing a Fourier transform. , The processing including a Fourier transform, based on the control signal the control signal reproducing unit is reproduced, the receiving section receives O
A transmission data demodulation unit for reproducing the transmission data from an FDM signal; 2. The transmission of an OFDM signal according to claim 1, wherein the transmission parameter specified by the control signal includes a parameter for specifying at least one of a modulation scheme, an interleave size, and an error correction type. system. 3. OFD including transmission data and control signal
An OFDM signal modulator for generating an M signal, comprising: a transmission data modulator for generating a transmission data modulation signal by modulating each subcarrier constituting an OFDM symbol based on the transmission data; Control signal modulating means for generating a control signal modulation signal by simultaneously modulating all subcarriers constituting a symbol with the same phase and amplitude based on the control signal; and the transmission data modulation signal and the control signal An OFDM signal modulation device, comprising: an OFDM signal generation unit configured to generate an OFDM signal in which a transmission data portion including the transmission data and a control signal portion including the control signal are multiplexed on a time axis based on a modulation signal. 4. An OFDM signal demodulation device for demodulating a received OFDM signal to reproduce transmission data, comprising: a control signal reproducing means for directly reproducing a control signal from the OFDM signal without performing a Fourier transform. By a process including a Fourier transform, based on a transmission parameter indicated by the control signal reproduced by the control signal reproducing means,
An OFDM signal demodulation device, comprising: transmission data reproducing means for reproducing the transmission data from the OFDM signal. 5. A control signal reproducing unit, comprising: a correlation unit for obtaining a correlation value between an OFDM symbol corresponding to the control signal included in the received OFDM signal and a time-domain reference signal prepared in advance; The OFDM signal demodulation apparatus according to claim 4, further comprising: a determination unit configured to determine the phase and the amplitude indicated by the correlation value obtained by the unit and to reproduce the control signal. 6. A transmission data reproducing means, comprising: a Fourier transform means for performing a Fourier transform on a received OFDM signal; a data demodulating means for demodulating an output of the Fourier transform means; and a deinterleaving means for deinterleaving an output of the data demodulating means. The OFDM signal demodulation device according to claim 4, further comprising: an interleaving unit; and an error correction unit that corrects an error of an output of the deinterleaving unit. 7. OFD including transmission data and control signal
An OFDM signal transmitting apparatus for transmitting an M signal, comprising: a transmission data modulation unit that generates a transmission data modulation signal by modulating each subcarrier forming an OFDM symbol based on the transmission data; Control signal modulating means for generating a control signal modulation signal by simultaneously modulating all subcarriers constituting a symbol with the same phase and amplitude based on the control signal; and the transmission data modulation signal and the control signal An OFDM signal generating means for generating an OFDM signal in which a transmission data portion including the transmission data and a control signal portion including the control signal are multiplexed on a time axis based on the modulated signal; OFDM
An OFDM signal transmission device, comprising: transmission means for transmitting a signal. 8. An OFDM signal receiving apparatus for receiving an OFDM signal and regenerating transmission data, comprising: a receiving means for receiving the OFDM signal; and without performing a Fourier transform from the OFDM signal received by the receiving means. A control signal reproducing means for directly reproducing a control signal, and a process including a Fourier transform, based on a transmission parameter indicated by the control signal reproduced by the control signal reproducing means,
Transmission data reproducing means for reproducing the transmission data from the OFDM signal received by the receiving means.
Signal receiver. 9. The control signal reproducing unit includes: a correlation unit that calculates a correlation value between an OFDM symbol corresponding to the control signal included in the OFDM signal received by the receiving unit and a time-domain reference signal prepared in advance. The OFDM signal receiving apparatus according to claim 8, further comprising: a determination unit configured to determine a phase and an amplitude indicated by the correlation value obtained by the correlation unit to reproduce the control signal. 10. The transmission data reproducing means, a Fourier transform means for performing a Fourier transform of the OFDM signal received by the receiving means, a data demodulating means for demodulating an output of the Fourier transform means, and an output of the data demodulating means. 9. The OFDM signal receiving apparatus according to claim 8, further comprising: a deinterleaver for deinterleaving; and an error correction unit for correcting an output of the deinterleaver. 11. An OF including transmission data and a control signal
An OFDM signal modulation method for generating a DM signal, comprising: generating a transmission data modulated signal by modulating each subcarrier constituting an OFDM symbol based on the transmission data; Generating a control signal modulation signal by simultaneously modulating all subcarriers having the same phase and amplitude based on the control signal, based on the transmission data modulation signal and the control signal modulation signal, Generating an OFDM signal in which a transmission data portion including the transmission data and a control signal portion including the control signal are multiplexed on a time axis.
Signal modulation method. 12. An OFDM signal demodulation method for demodulating a received OFDM signal to reproduce transmission data, the method comprising: directly reproducing a control signal from the received OFDM signal without performing a Fourier transform; Recovering the transmission data from the OFDM signal based on a transmission parameter indicated by the control signal by a process including a Fourier transform. 13. The step of reproducing the control signal, comprising: obtaining a correlation value between an OFDM symbol corresponding to the control signal included in the received OFDM signal and a previously prepared time domain reference signal; Regenerating the control signal by determining the phase and the amplitude indicated by the correlation value. 14. The step of reproducing the transmission data includes the steps of: performing a Fourier transform on the received OFDM signal; demodulating a result of the Fourier transform; deinterleaving the demodulated result; 13. The method of demodulating an OFDM signal according to claim 12, comprising the step of correcting an error. 15. An OF including transmission data and a control signal
An OFDM signal transmission method for transmitting a DM signal, comprising: generating a transmission data modulated signal by modulating each subcarrier constituting an OFDM symbol based on the transmission data; Generating a control signal modulation signal by simultaneously modulating all subcarriers having the same phase and amplitude based on the control signal, based on the transmission data modulation signal and the control signal modulation signal, Generating an OFDM signal in which a transmission data portion including the transmission data and a control signal portion including the control signal are multiplexed on a time axis; and transmitting the OFDM signal.
DM signal transmission method. 16. An OFDM signal receiving method for receiving an OFDM signal and reproducing transmission data, the method comprising: receiving the OFDM signal; and directly transmitting a control signal from the OFDM signal without performing a Fourier transform. An OFDM signal receiving method, comprising: reproducing the transmission data from the OFDM signal based on a transmission parameter indicated by the control signal by a process including a Fourier transform. 17. The method according to claim 17, wherein the step of reproducing the control signal comprises the step of reproducing the control signal corresponding to the control signal included in the OFDM signal.
17. A method according to claim 16, comprising: obtaining a correlation value between an FDM symbol and a previously prepared time-domain reference signal; and reproducing the control signal by determining a phase and an amplitude indicated by the correlation value. The OFDM signal receiving method as described in the above. 18. The step of recovering the transmission data includes the steps of: Fourier transforming the OFDM signal; demodulating the result of Fourier transform; deinterleaving the demodulated result; Correcting the OFDM signal.