JP2001339363A - Method for transmitting ofdm signal, transmitter and receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate transmission channel distortion, synchronization time deviation, frequency deviation, and temporal frequency response fluctuation due to phase noise so as to improve the demodulation characteristics. SOLUTION: A pilot symbol detection section 261 of the receiver receiving an OFDM signal detects a pilot symbol. A 1st pilot symbol transmission channel frequency response calculation section 62 obtains a 1st pilot symbol transmission channel frequency response, and a 2nd pilot symbol transmission channel frequency response calculation section 63 obtains a 2nd pilot symbol transmission channel frequency response. Moreover, a compensation vector calculation section 64 obtains a compensation vector through straight line approximation from the 1st and 2nd pilot symbol transmission channel frequency responses. A frequency response compensation section 65 compensates the fluctuation in the frequency response of the subcarrier of a data symbol on the basis of the obtained compensation vector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal frequency division multiplex (Orthogonal Frequency Div.).
edition Multiplexing: Hereinafter, OFD
More specifically, the present invention relates to a method of transmitting data using an OFDM signal via a wired or wireless transmission path, and a transmission / reception apparatus thereof.

[0002]

2. Description of the Related Art In an OFDM transmission system, an amplitude error and a phase due to a distortion in a transmission line, a time synchronization deviation, a frequency deviation between a transmitting side and a receiving side, a phase noise in a local oscillator of a receiver, and the like. It is known that errors cause degradation of demodulation characteristics. The error factor of the received signal which causes the deterioration of the demodulation characteristics as described above is hereinafter referred to as frequency response fluctuation.

Here, generally, in transmission of an OFDM signal, a transmitter inserts a preamble portion having a time length longer than one symbol length into a signal to be transmitted in order to synchronize with a receiver. There are many. By using the preamble part, the frequency response of the transmission path can be accurately estimated. Of course, if the preamble portion is frequently inserted, the frequency response of the transmission path can be accurately estimated, but the transmission speed is significantly reduced.

Therefore, conventionally, as shown in Japanese Patent Application Laid-Open No. 8-265293, for example, a method of inserting one or a plurality of pilot carriers between data carriers in a data symbol is adopted.

[0005] An OFDM signal is composed of a plurality of symbols having a certain time length and including some subcarriers. Both the data carrier and the pilot carrier described above are one of the subcarriers. In the above-described conventional example, for each data symbol, a phase error of a pilot carrier included in the data symbol is detected, and the error is compensated.

[0006]

However, according to the above-described conventional example, the number of pilot carriers per symbol in an environment where a large noise is generated in a transmission path or in a multipath fading environment. If the number is small, there is a problem that the detection accuracy of the phase error is deteriorated. Further, if the number of pilot carriers is increased, the detection accuracy of the phase error can be improved, but on the other hand, there is a problem that the occupied frequency bandwidth is widened and the transmission speed is reduced. Also, it is difficult to compensate for an amplitude error caused by transmission line distortion.

Accordingly, the present invention provides a method for accurately correcting transmission line distortion, time synchronization deviation, and transmission / reception without reducing the transmission speed even in an environment where large noise is generated in the transmission path or in a multipath fading environment. A method of compensating for the frequency response of the transmission path and the fluctuation of the frequency response of the transmission line caused by any one or more of the residual phase errors for all the subcarriers included in the symbol and transmitting the OFDM signal at a low error rate. It is an object of the present invention to provide a transmission / reception device therefor.

[0008]

A first aspect of the present invention is a method of transmitting an OFDM signal from a transmitting side to a receiving side, wherein the OFDM signal includes a data symbol composed of data and a predetermined symbol. At the transmitting end, the pilot symbols are inserted before or after one or more data symbols, transmitted with the data symbols, and received at the receiving end. The pilot symbol is used for compensating fluctuation of a frequency response of a transmission line caused by one or more of transmission line distortion, time synchronization deviation, frequency deviation, and residual phase error of a received data symbol.

As described above, in the first aspect, a pilot symbol having a predetermined frequency component and a subcarrier amplitude and phase having a predetermined pattern is inserted for each predetermined number of data symbols on the transmission side. On the receiving side, the frequency response of the transmission path is accurately estimated using the pilot symbols. Based on this estimation result and the frequency response difference between two pilot symbols separated by a time length of a predetermined number of data symbols, the frequency response fluctuation of the data symbols between the pilot symbols is compensated. By doing so, it is possible to accurately demodulate data symbols even in a multipath fading environment or an environment where large noise occurs.

[0010] A second invention is an invention according to the first invention, wherein all the subcarriers constituting the pilot symbol are pilot carriers having a predetermined amplitude and phase.

As described above, in the second aspect, the number of subcarriers per symbol does not affect the symbol length. Therefore, even if all the subcarriers are included, a transmission method of an OFDM signal can be realized in which the transmission speed does not decrease and the phase error can be corrected more accurately.

A third invention is an invention according to the first invention, wherein a plurality of pilot symbols are continuously inserted before or after one or a plurality of data symbols. .

As described above, in the third invention, if a plurality of pilot symbols are continuously inserted, the accuracy of estimating the frequency response of the transmission path on the receiving side is improved, and a multipath fading environment and large noise occur. Environment,
Data symbols can be demodulated more accurately.

A fourth invention is the invention according to the first invention, wherein pilot symbols are periodically inserted before or after one or a plurality of data symbols.

As described above, in the fourth aspect, when pilot symbols are periodically inserted, it is easy to find the temporal position of the pilot symbols at the time of reception.

A fifth invention is the invention according to the first invention, wherein the pilot symbol is aperiodically inserted before or after one or more data symbols.

As described above, in the fifth invention, when the pilot symbols are inserted at non-periodic or irregular intervals, the insertion interval can be selected according to the speed of change of the transmission path.

A sixth invention is an invention according to the fifth invention, wherein an insertion interval and the number of insertions when a pilot symbol is inserted into a data symbol on the transmitting side are adaptive according to the condition of the transmission path. It is characterized in that it is adjusted so as to change.

As described above, in the sixth aspect, the transmission efficiency can be improved by adaptively changing the number and interval of insertion of pilot symbols according to the conditions of the transmission path.

A seventh invention is the invention according to the fifth invention, wherein the insertion interval and the number of insertions when the pilot symbol is inserted into the data symbol on the transmitting side are included in the OFDM signal as control information. It is characterized by.

As described above, in the seventh aspect of the present invention, the control information is included in the transmission signal by including, as control information, the intervals at which pilot symbols are inserted into data symbols and the number of pilot symbols to be inserted per location. Demodulation can be performed based on the distinction between pilot symbols and data symbols.

An eighth invention is an invention according to the first invention, wherein the time-series linear approximation value is obtained by compensating for the fluctuation of the frequency response of the transmission line from the difference in the frequency response between the nearest pilot symbols. The compensation vector calculated as is used.

As described above, in the eighth aspect, the frequency response fluctuation of the data symbol between the pilot symbols is compensated using the linear approximation. Then, since the phase change due to the frequency shift between the pilot symbols has linearity in the time series, linearly accurate compensation can be performed. Furthermore, if the insertion interval of the pilot symbols is properly selected, the transmission line frequency response has linearity, so that it is possible to compensate linearly and accurately.

A ninth invention is a invention according to the first invention, wherein the variation of one or both of the frequency shift and the residual phase error is compensated for by using the phase difference value between the nearest pilot symbols. It is characterized in that a value calculated as a series straight line approximate value is used.

As described above, in the ninth aspect, the phase error of the data symbol between the pilot symbols is compensated using the linear approximation. Then, since the phase change due to the frequency shift has linearity in the time series, linearly accurate compensation can be performed.

A tenth invention is an invention according to the first invention, wherein an average value of phase differences of pilot carriers constituting pilot symbols is used for compensating fluctuation of a frequency response of a transmission line. Features.

As described above, in the tenth aspect, by averaging the phase of the received pilot carrier, the OF can be corrected with higher accuracy.
A method of transmitting a DM signal can be realized.

An eleventh invention is an invention according to the tenth invention, wherein the average value is calculated by weighting with an amplitude value of each pilot carrier.

As described above, in the eleventh invention, the received signal is distorted by the transmission path and the noise. for that reason,
An average value is obtained by performing weighting according to the amplitude value of each carrier of the received pilot symbol. By doing so, an OFDM signal that can correct the phase error more accurately can be obtained.
A signal transmission method can be realized.

A twelfth invention is directed to an OFDM
A transmission device for transmitting a signal, comprising: a data symbol generation unit that receives an input of transmission data and generates an OFDM data symbol; a pilot symbol generation unit that generates an OFDM pilot symbol; Or a symbol selection unit that switches and outputs signals input from the data symbol generation unit and the pilot symbol generation unit so that pilot symbols are inserted later.

As described above, in the twelfth aspect, the transmitting apparatus inserts a pilot symbol having a predetermined frequency component and a predetermined pattern in amplitude and phase for each predetermined number of data symbols. Next, the receiving side accurately compensates for the fluctuation of the frequency response of the data symbol using the pilot symbol. Then, data symbols can be transmitted accurately even in a multipath fading environment or an environment where large noise is occurring.

A thirteenth invention is the invention according to the twelfth invention, wherein the data symbol generation unit receives the transmission data and generates a data symbol on the frequency axis. And an inverse Fourier transform unit that performs an inverse Fourier transform on a signal from the data symbol generation unit on the frequency axis, wherein the pilot symbol generation unit generates a pilot symbol on the frequency axis that generates a pilot symbol on the frequency axis; An inverse Fourier transform unit for performing an inverse Fourier transform on the signal from the on-axis pilot symbol generation unit.

As described above, according to the thirteenth aspect, the transmitting apparatus firstly sets a pilot symbol having a predetermined frequency component and a subcarrier amplitude and phase having a predetermined pattern, and a data symbol on the frequency axis. And performs an inverse Fourier transform. Then, an OFDM signal can be generated with a simple configuration, and data symbols can be accurately transmitted with a simple configuration even in a multipath fading environment or an environment where large noise is occurring.

According to a fourteenth aspect of the present invention, a data symbol transmitted from the transmitting side and configured by data, has a predetermined frequency component, amplitude and phase, and is inserted before or after one or more data symbols. A receiver for receiving an OFDM signal including a pilot symbol, a Fourier transform unit for performing a Fourier transform on the received OFDM signal, and detecting a pilot symbol from a signal output from the Fourier transform unit, and detecting a pilot symbol from the Fourier transform unit. A transmission line frequency response compensator for compensating for a change in the frequency response of the transmission line with respect to the output signal; and a demodulation unit for receiving a signal compensated for the change in the frequency response of the transmission line and outputting demodulated data. Is provided.

As described above, in the fourteenth aspect, a pilot symbol having a predetermined frequency component on the transmitting side and a subcarrier amplitude and phase having a predetermined pattern is inserted for each predetermined number of data symbols. On the side, the amount of frequency response fluctuation is accurately detected using pilot symbols. By doing so, it is possible to accurately demodulate data symbols even in a multipath fading environment or an environment where large noise occurs.

A fifteenth invention is a invention according to the fourteenth invention, wherein the transmission line frequency response compensator includes a frequency response of a pilot symbol and a frequency response of a pilot symbol closest to the pilot symbol. And using a frequency response of a reference pilot symbol prepared on the receiving side to calculate and compensate a compensation vector such that the frequency response of the received data symbol matches the frequency response of the reference pilot symbol. .

As described above, in the fifteenth aspect, a pilot symbol having a predetermined frequency component on the transmitting side and a subcarrier amplitude and phase having a predetermined pattern is inserted for each predetermined number of data symbols. On the side, the transmission line frequency response is accurately estimated using pilot symbols. From this result and the frequency response difference between two pilot symbols separated by a time length of a predetermined number of data symbols, if the frequency response fluctuation of the data symbols between the pilot symbols is compensated, a multipath fading environment and large noise will occur. The data symbols can be accurately demodulated even in an environment where the data symbols are generated.

A sixteenth invention is an invention according to the fifteenth invention, wherein a compensation vector uses all pilot carriers included in each pilot symbol and all subcarriers included in a received data symbol. , Respectively.

As described above, in the sixteenth aspect, since the compensation vector is calculated individually for each subcarrier, it is used when transmission line distortion or time synchronization shift occurs, for example, when used in mobile communication. Also, the data symbol can be accurately demodulated by compensating for the frequency response fluctuation.

A seventeenth aspect is the invention according to the fifteenth aspect, wherein the compensation vector is calculated as a time-series linear approximation from the frequency response variation between the closest pilot symbols. And

As described above, in the seventeenth aspect, the frequency response fluctuation of the data symbol between the pilot symbols is compensated using the linear approximation. Then, when the transmission path fluctuation can be regarded as a linear fluctuation between pilot symbols to be inserted, linearly accurate compensation can be performed.
Further, since the phase fluctuation due to the frequency shift has a linearity in a time series, a linear compensation effect is exhibited.

An eighteenth invention is an invention according to the fourteenth invention, wherein the transmission line frequency response compensator includes a first pilot symbol which is an arbitrary pilot symbol, and a first pilot symbol after the first pilot symbol. A pilot symbol detecting unit for detecting a transmitted second pilot symbol; and a frequency division response of the first pilot symbol divided by a frequency response of a reference pilot symbol prepared on the receiving side. A first pilot symbol transmission line frequency response calculation unit for calculating a transmission line frequency response; and a second pilot symbol transmission line frequency response by dividing the frequency response of the second pilot symbol by the frequency response of the reference pilot symbol. A second pilot symbol transmission line frequency response calculating section, and first and second pilot symbols. And a compensation vector calculation unit for receiving a frequency response of the transmission symbol and calculating a compensation vector for compensating for a variation in the frequency response of the transmission line. And parts.

As described above, in the eighteenth aspect, the transmitting side inserts a pilot symbol having a predetermined frequency component and a predetermined pattern in amplitude and phase for each predetermined number of data symbols. At the receiving side, a first pilot symbol and a second pilot symbol detected first from a received signal are divided by a predetermined reference pilot symbol prepared at the receiving side to obtain a transmission path for the first and second pilot symbols. Find the frequency response of Next, a difference between the transmission line frequency response of the first pilot symbol and the transmission line frequency response of the second pilot symbol is obtained. A compensation vector for the data symbol can be obtained from the transmission line frequency response difference between the pilot symbols. Therefore, it is possible to accurately compensate for transmission line distortion, time synchronization shift, frequency shift and residual phase error of data symbols.

According to a nineteenth aspect of the present invention, a data symbol transmitted from the transmitting side and configured by data, has a predetermined frequency component, an amplitude and a phase, and is inserted before or after one or a plurality of data symbols. A receiving device for receiving an OFDM signal including
A Fourier transform unit for performing a Fourier transform on the received OFDM signal; a pilot symbol detected from a signal output from the Fourier transform unit; and compensation for one or both of a frequency shift and a residual phase error of the signal output from the Fourier transform unit. And a demodulation unit that receives a signal compensated for one or both of the frequency shift and the residual phase error and outputs demodulated data.

As described above, in the nineteenth aspect, a pilot symbol having a predetermined frequency component and a predetermined amplitude and phase having a predetermined pattern is inserted for each predetermined number of data symbols on the transmission side, and , The phase error is accurately detected using the pilot symbols. By doing so, it is possible to accurately demodulate data symbols even in a multipath fading environment or an environment where large noise occurs.

According to a twentieth aspect, in accordance with the nineteenth aspect, the phase compensator includes a phase difference value between a phase of a certain pilot symbol and a predetermined phase, and a phase difference between the closest pilot symbols. The phase difference value is used to calculate and compensate a phase compensation value such that the phase of the received data symbol matches a predetermined phase.

As described above, according to the twentieth aspect, a pilot symbol having a predetermined frequency component and having a predetermined pattern in amplitude and phase is inserted for each predetermined number of data symbols on the transmission side, and , The phase error is accurately detected using the pilot symbols. This detection result,
By compensating for the phase error of data symbols between pilot symbols from the phase difference between two pilot symbols separated by the time length of a predetermined number of data symbols, even in a multipath fading environment or an environment where large noise is occurring. Data symbols can be demodulated accurately.

A twenty-first invention is an invention according to the twentieth invention, wherein the phase difference value is calculated using an average value of phases of all pilot carriers included in each pilot symbol. And

As described above, according to the twenty-first aspect, by averaging the phases of the received pilot carriers, the OF can be corrected with higher accuracy.
A DM signal receiving apparatus can be realized.

A twenty-second invention is the invention according to the twenty-first invention, wherein the average value is calculated by weighting the average value with the amplitude value of each pilot carrier.

As described above, in the twenty-second aspect, the received signal is distorted by the transmission path and the noise. for that reason,
An average value is obtained by performing weighting according to the amplitude value of each carrier of the received pilot symbol. By doing so, an OFDM signal that can correct the phase error more accurately can be obtained.
A signal receiving device can be realized.

A twenty-third invention is the invention according to the twentieth invention, wherein the compensation value is calculated as a time-series linear approximation from the phase difference value between the closest pilot symbols. I do.

As described above, in the twenty-third aspect, the phase error of the data symbol between the pilot symbols is compensated using the linear approximation. Then, since the phase change due to the frequency shift has linearity in the time series, linearly accurate compensation can be performed.

A twenty-fourth invention is an invention according to the nineteenth invention, wherein the phase compensator is transmitted after a first pilot symbol which is an arbitrary pilot symbol and the first pilot symbol. A pilot symbol detector for detecting a second pilot symbol, a first pilot symbol phase difference calculator for calculating a difference between a phase of the first pilot symbol and a predetermined phase, and a phase of the first pilot symbol. A phase difference calculating section for calculating a difference between the phase of the second pilot symbol and a phase difference value calculated by the phase difference calculating section for the first pilot symbol; And a phase compensation value calculator for calculating a compensation value for correcting a frequency shift and a residual phase error. It is, and a phase rotator for rotating the phase of the data symbol.

As described above, according to the twenty-fourth aspect, on the transmitting side, a pilot symbol having a predetermined frequency component and having a predetermined pattern in amplitude and phase is inserted for each predetermined number of data symbols. On the receiving side, the phase difference between the first pilot symbol detected first from the received signal and a predetermined reference pilot symbol prepared on the receiving side is determined. Next, a first pilot symbol,
A phase difference with a later detected second pilot symbol is determined. As a result, the phase error between the two pilot symbols is obtained, and the phase compensation value for the data symbol can be obtained. Therefore, it is possible to accurately compensate for the frequency shift and the residual phase error of the data symbol.

[0056]

(First Embodiment) First, a transmission method according to a first embodiment of the present invention will be described. FIG.
FIG. 3 is a diagram illustrating a configuration of an OFDM signal transmitted in the transmission method according to the first embodiment of the present invention. As shown in FIG. 1, a plurality of data symbols follows a pilot symbol having a predetermined frequency component and having a predetermined pattern in amplitude and phase. After the data symbol, a pilot symbol follows. Thus, the O in the transmission method according to the first embodiment of the present invention is
The FDM signal has a configuration in which pilot symbols are inserted before and after one or more data symbols. Note that one pilot symbol may be inserted,
It may be a continuous plural.

Here, the OFDM signal includes several subcarriers, but the number of subcarriers per symbol does not affect the symbol length. Therefore, all subcarriers may have a predetermined amplitude and phase,
Some of the subcarriers may have a predetermined amplitude and phase. However, in order to accurately compensate for the frequency response fluctuation, it is preferable that all the subcarriers have a predetermined amplitude and phase.

As described above, in transmission of an OFDM signal, the transmitter is required to synchronize with the receiver.
In many cases, a preamble part having a time length longer than the symbol length is inserted into a signal to be transmitted. In FIG. 1, the preamble portion may be inserted at the start of transmission, or may be inserted at appropriate intervals. Of course, if the preamble part is frequently inserted, the frequency response fluctuation can be corrected with high accuracy, but the transmission speed is significantly reduced. Therefore, according to the transmission method according to the first embodiment of the present invention, it is preferable that the preamble portion is inserted at the start of transmission or is inserted less frequently.

Further, the preamble part may include, as control information, an interval and number of pilot symbols inserted into data symbols. Then, the control information can be analyzed on the receiving side to distinguish pilot symbols and data symbols.

Further, the control information may be inserted as a data symbol or a control information symbol after the first pilot symbol. Then, the normal OFDM
The control information can be demodulated as a signal without error.

Thus, on the transmitting side, the pilot symbols are inserted before and after one or more data symbols, transmitted together with the data symbols, and the above-described OFDM signal is transmitted. Then, on the receiving side, the frequency response of the transmission path is accurately estimated using the pilot symbols.

The frequency response fluctuation of the data symbols between the pilot symbols is compensated based on the estimation result and the difference in the transmission line frequency response between two pilot symbols separated by the time length of a predetermined number of data symbols. By doing so, it is possible to realize a transmission method that can accurately demodulate data symbols even in a multipath fading environment or an environment where large noise is occurring.

Here, in FIG. 1A, the pilot symbol before the data symbol is defined as a first pilot symbol, and the pilot symbol following the data symbol is defined as a second pilot symbol. Further, the time interval between the first pilot symbol and the second pilot symbol is set such that the interval between insertion of the pilot symbols is increased when the fluctuation of the transmission path is small, and the pilot interval is increased when the fluctuation of the transmission path is large. The insertion interval is shortened to such an extent that the variation of the transmission path between symbols becomes linear. As described above, the transmission efficiency can be increased by adaptively changing the intervals at which the pilot symbols are inserted according to the conditions of the transmission path.

The status of the transmission path may be measured and determined on the transmission side, or the status of the transmission path measured by the reception side may be fed back to the transmission side and determined on the transmission side.

Further, pilot symbols may be inserted periodically or aperiodically. When pilot symbols are periodically inserted, it becomes easy to detect the temporal position of the pilot symbols when receiving. In the case of insertion at non-periodic or irregular intervals, the insertion interval can be selected according to the speed of change of the transmission path. The case where the pilot symbols are inserted aperiodically or at irregular intervals means that the pilot symbols are not periodically inserted over the entire period of signal transmission. Does not exclude the case where pilot symbols are periodically inserted in some periods in.

Here, in the case of being inserted aperiodically,
As shown in FIG. 1B, a control information symbol including control information indicating an interval and the number of pilot symbols to be inserted is inserted immediately after the first pilot symbol. By arranging the control information in this way, the control information can be demodulated based on the transmission line frequency response estimated with the first pilot symbol. Therefore, demodulation can be performed more accurately than when the signal is included in the preamble portion.

The first pilot symbol may be composed of two pilot symbols as shown in FIG. 1C in order to improve the accuracy of estimating the transmission line frequency response in the pilot symbol portion. Also,
As shown in FIG. 1D, two pilot symbols may be inserted, or three or more pilot symbols may be continuously inserted. In such a case, the transmission line frequency response of each pilot symbol can be accurately estimated by averaging the transmission line frequency response of each pilot symbol.

The OFDM signal having the above configuration can be generated, for example, by the following transmitting apparatus. FIG. 2 is a schematic diagram illustrating a configuration of the transmission device according to the first embodiment of the present invention. In the following, the number of data symbols is M, and the number of subcarriers per symbol is N.

In FIG. 2, the transmitting apparatus has an OFDM data symbol generating section 1 for generating a data symbol from input transmission data, and has a predetermined frequency component as described above, and its amplitude and phase are predetermined. OFDM pilot symbol generation unit 2 for generating pilot symbols having the following pattern, and two signals from OFDM data symbol generation unit 1 and OFDM pilot symbol generation unit 2 are input, and any one of them is selected and output. And a D / A converter 4 that converts digital data output from the symbol selector 3 into analog data and outputs a transmission signal.

FIG. 3 is a block diagram showing a detailed configuration of OFDM data symbol generation section 1 and OFDM pilot symbol generation section 2 in the transmitting apparatus according to the first embodiment of the present invention. In FIG. 3A,
The OFDM data symbol generation unit 1 includes a frequency-axis data symbol generation unit 11 and an inverse Fourier transform unit 12. In FIG. 3B, the OFDM pilot symbol generator 2 includes a frequency-axis pilot symbol generator 21 and an inverse Fourier transformer 22.

Here, in FIG. 2, data to be transmitted is input to the OFDM data symbol generation unit 1. The input data is converted into data symbols and input to the symbol selection unit 3.

More specifically, in FIG. 3A, data to be transmitted is first input to the on-frequency data symbol generation unit 11. The on-frequency-data symbol generator 11 outputs on-frequency data symbols composed of a number of data carriers arranged at predetermined intervals on the frequency axis. The data symbols on the frequency axis are subjected to inverse Fourier transform by the inverse Fourier transform unit 12 and converted into OFDM data symbols arranged on the time axis. The converted OFDM data symbols are input to symbol selection section 3.

On the other hand, a pilot symbol having a predetermined frequency component as described above and having a predetermined pattern in its amplitude and phase is generated by the OFDM pilot symbol generation unit 2.
And input to the symbol selection unit 3.

More specifically, in FIG. 3B, the pilot symbol on the frequency axis is composed of a number of pilot carriers arranged at predetermined intervals on the frequency axis by the pilot symbol on the frequency axis 21. Is output. The pilot symbols on the frequency axis are subjected to inverse Fourier transform by the inverse Fourier transform unit 22, and are converted into OFDM pilot symbols arranged on the time axis. The converted OFDM pilot symbols are input to symbol selection section 3.

The symbol selection section 3 selects and outputs one of the two signals input as described above. For example, the symbol selection unit 3 is configured as shown in FIG. 1 in which one pilot symbol is inserted for every three data symbols.
It is assumed that a signal as shown in FIG.

In such a case, the symbol selector 3 first selects a signal from the OFDM pilot symbol generator 2. The symbol selection unit 3 selects a signal from the OFDM data symbol generation unit 1 at the timing when one pilot symbol has been output. After that, the symbol selection unit 3 selects a signal from the OFDM pilot symbol generation unit 2 at the timing when the output of three data symbols is completed. Further, the symbol selection unit 3 selects the signal from the OFDM data symbol generation unit 1 again at the timing when one pilot symbol has been output. Then, the symbol selection unit 3 successively switches signals to be selected in the same manner as described above, and
An OFDM signal as shown in (a) can be continuously output.

As described above, the signal output from symbol selection section 3 is input to D / A conversion section 4. D /
The A conversion unit 4 converts the input signal from digital data to analog data and outputs it as a transmission signal.

As described above, the transmitting apparatus according to the first embodiment of the present invention inserts a pilot symbol having a predetermined frequency component and a predetermined pattern in amplitude and phase for every predetermined number of data symbols. I do. By using such a transmission device, if the reception side accurately compensates for the variation in the frequency response of data symbols using pilot symbols, the data can be accurately obtained even in a multipath fading environment or an environment where large noise is occurring. Symbols can be transmitted.

Next, FIG. 4 is a schematic diagram showing the configuration of the receiving apparatus according to the first embodiment of the present invention. 4, the present receiving apparatus includes a Fourier transform unit 5 that performs a Fourier transform on an input received signal, a transmission line frequency response compensating unit 6 that compensates for a change in the frequency response of the signal output from the Fourier transform unit 5, A demodulation unit 7 for demodulating the signal output from the transmission line frequency response compensation unit 6;

In FIG. 4, a Fourier transform unit 5 performs a Fourier transform on each symbol and outputs frequency domain data. From the output data, the transmission line frequency response compensator 6 removes fluctuations in the frequency response of the transmission line. Further, the data from which the frequency response fluctuation has been removed is demodulated by the demodulation unit 7 as a data symbol.

Next, FIG. 5 is a schematic diagram showing in detail the configuration of the transmission line frequency response compensator in the receiving apparatus according to the first embodiment of the present invention. In FIG. 5, a transmission line frequency response compensator 6 in the receiving apparatus includes a pilot symbol detector 61 that detects a pilot symbol from a signal output from the Fourier transformer 5 and a first symbol output from the pilot symbol detector 61. A first pilot symbol transmission line frequency response calculator 62 for calculating a value obtained by dividing the pilot symbol by the reference pilot symbol, and a value obtained by dividing the second pilot symbol output from the pilot symbol detector 61 by the reference pilot symbol. Second pilot symbol transmission line frequency response calculation section 63
And a first pilot symbol transmission line frequency response calculation unit 6
A compensation vector calculation unit 64 that receives the output from the second and second pilot symbol transmission channel frequency response calculation unit 63 and calculates a compensation vector, and an output from the pilot symbol detection unit 61 based on the output from the compensation vector calculation unit 64 And a frequency response compensator 65 for compensating the frequency response of the signal.

In FIG. 5, a pilot symbol detector 61 calculates the frequency domain data from the Fourier transformed
Detect pilot symbols. First pilot symbol transmission line frequency response calculation section 62 includes the subcarriers included in the first pilot symbol in a reference pilot symbol stored in a memory or the like (not shown) provided in the receiving device. Divide by subcarrier,
Estimate the frequency response of the transmission path.

The reference pilot symbols stored in this memory are ideal pilot symbols, similar to a state where there is no frequency response fluctuation error at the time of reception. Therefore, by dividing the frequency response of the subcarrier included in the first pilot symbol by the subcarrier included in the reference pilot symbol, the frequency response of the transmission path can be obtained.

FIG. 6 is a schematic diagram showing subcarriers included in a first pilot symbol having a complex amplitude of P1 and subcarriers included in a reference pilot symbol having a complex amplitude of Pr. The first pilot symbol transmission line frequency response calculation unit 62 calculates the complex amplitude P1 of the subcarrier included in the first pilot symbol as shown in FIG. 6A, as shown in FIG.
The frequency response Pa of the transmission path is calculated by dividing by the complex amplitude Pr of the subcarrier included in the reference pilot symbol stored in the memory on the receiving side. The calculation formula is as shown in the following formula (1).

Pa (i) = P1 (i) ÷ Pr (i) (1) where i is any integer from 1 to N.

As described above, when a plurality of pilot symbols are continuously inserted, the transmission line frequency response of each pilot symbol is averaged and used. Then, it is possible to more accurately estimate the transmission line frequency response of the pilot symbol.

In FIG. 5, second pilot symbol transmission line frequency response calculation section 63 includes a subcarrier included in the second pilot symbol in a reference pilot symbol stored in a memory or the like provided in the receiving device. And the frequency response of the transmission path in the second pilot symbol is estimated.

FIG. 7 is a schematic diagram showing subcarriers included in a second pilot symbol having a complex amplitude of P2 and subcarriers included in a reference pilot symbol having a complex amplitude of Pr. The second pilot symbol transmission line frequency response calculation unit 63 calculates the complex amplitude P2 of the subcarrier included in the second pilot symbol as shown in FIG. 7A, as shown in FIG.
The frequency response Pb of the transmission path is calculated by dividing by the complex amplitude Pr of the subcarrier included in the reference pilot symbol stored in the memory on the receiving side. The calculation formula is as shown in the following formula (2).

Pb (i) = P2 (i) ÷ Pr (i) (2) where i is any integer from 1 to N.

When a plurality of consecutive second pilot symbols are inserted, the transmission path frequency response of each pilot symbol is averaged to more accurately transmit the transmission path of the second pilot symbol. As described above, the frequency response can be estimated.

Compensation vector calculation section 64 converts compensation vector Vk for each data symbol existing between the first pilot symbol and the second pilot symbol into first pilot symbol transmission line frequency response Pa and second pilot symbol transmission line frequency. It is determined by linear approximation obtained from the response Pb. Here, it is determined by linear approximation because pilot symbols are inserted at short intervals so that the fluctuation of the transmission path becomes linear, and phase fluctuation due to frequency shift has linearity in time series. is there. Therefore, according to the linear approximation, linearly accurate compensation can be performed.

FIG. 8 shows the case where the first pilot symbol
5 is a graph showing the relationship between the compensation vector Vk for each data symbol existing between pilot symbols on the vertical axis and the number of each symbol, that is, time, on the horizontal axis. As shown in FIG. 8, it can be seen that the compensation vector Vk for each data symbol can be obtained by linear approximation from the difference in the transmission line frequency response between pilot symbols.

Here, from the first pilot symbol to the second pilot symbol
The number of data symbols existing between pilot symbols is M, and a certain data symbol existing between the first pilot symbol and the second pilot symbol is k. Here, k is an arbitrary integer from 1 to M.
On the premise of the above, a mathematical expression for calculating the compensation vector Vk for each data symbol by the above-described linear approximation can be expressed as the following expression (3).

(Equation 1) Here, k is an arbitrary integer from 1 to M.

Next, the frequency response compensating section 65 calculates the frequency response fluctuation of the subcarrier included in each data symbol existing between the first pilot symbol and the second pilot symbol by using the compensation vector obtained as described above. To compensate.

FIG. 9 is a schematic diagram showing how the frequency response fluctuation in the k-th data symbol is compensated. The frequency response fluctuation of the subcarrier included in each data symbol is compensated from the obtained compensation vector as in the following equation (4). C′k (i) = Ck (i) / Vk (i) (4)

The above-mentioned compensation for the frequency response fluctuation of the data symbols is performed for k data symbols existing between the first pilot symbol and the second pilot symbol. Therefore, actually, these data symbols are temporarily stored in, for example, a data symbol storage unit (not shown) provided in the receiving apparatus. After the compensation vector is calculated, the data symbol stored in the data symbol storage unit is read, and the frequency response fluctuation is compensated for.

Typically, a data symbol storage unit (not shown) is provided before or inside frequency response compensation unit 65. Then, each data symbol stored in the data symbol storage unit is stored in the compensation vector calculation unit 6.
4, the compensation vector Vk for each data symbol
Is calculated, the frequency response compensator 65 compensates for the frequency response fluctuation.

Therefore, in the method used in the present receiver according to the first embodiment, demodulation cannot be performed from the reception of the first pilot symbol to the reception of the second pilot symbol, so that a certain processing time is required. Take it. Therefore, this method is more suitable for a video transmission in which retransmission is not required immediately or a reception method used in broadcast-type transmission.

As described above, it is possible to calculate the compensation vector for compensating the variation of the frequency response caused by the variation of the transmission path of each subcarrier included in the pilot symbol. In this regard, it is possible to calculate the compensation vector for all the subcarriers more accurately than the conventional method of inserting a pilot carrier into each data symbol. Because the number of pilot carriers inserted by the conventional method is extremely small compared to the number of all subcarriers, the conventional method accurately calculates the frequency response fluctuation of the transmission line over the entire frequency band. It is difficult to do so.

In this way, the frequency response compensator 65
Can remove the fluctuation of the frequency response in the transmission path of the input data. In particular, when the variation of the transmission path can be regarded as a linear variation between pilot symbols, by compensating the frequency response of the data symbols between the pilot symbols using a linear approximation, it is possible to reduce the multipath fading environment and the large Data symbols can be accurately demodulated even in an environment where noise is generated. Further, since the phase change due to the frequency shift has a linearity in a time series, it is possible to perform linearly accurate compensation.

When the fluctuation of the transmission path is small, 2
Compensation for a transmission line frequency response variation in a data symbol between two pilot symbols may be performed only with a pilot symbol that is temporally earlier in the two pilot symbols. By doing so, it is possible to compensate for the transmission line frequency response fluctuation of the data symbol without receiving the subsequent pilot symbol.

(Second Embodiment) The transmission method according to the second embodiment of the present invention is almost the same as that of the first embodiment. The configuration of the transmitting device according to the second embodiment of the present invention is the same as the configuration of the transmitting device according to the above-described first embodiment, and thus the description thereof will be omitted. However, the configuration of the receiving apparatus according to the second embodiment of the present invention is partially different from the configuration of the receiving apparatus according to the above-described first embodiment, and thus the following description will focus on the differences.

FIG. 10 is a schematic diagram showing a configuration of a receiving apparatus according to the second embodiment of the present invention. In FIG. 10, the receiving apparatus includes a Fourier transform unit 5 and a phase compensating unit 2 for compensating the phase of the signal output from the Fourier transform unit 5.
6 and a demodulation unit 7 for demodulating the signal output from the phase compensation unit 26. Therefore, the present receiver includes a phase compensator 26 instead of the transmission line frequency response compensator 6 in the receiver of FIG.

In FIG. 10, the data output from the Fourier transform unit 5 is subjected to a phase compensation unit 26 to remove a frequency shift and a residual phase error. The detailed configuration of the phase compensator 26 will be described later. Further, the data from which the error has been removed is demodulated by the demodulation unit 7.

Next, FIG. 11 is a schematic diagram showing in detail the configuration of the phase compensator 26 in the receiving apparatus according to the second embodiment of the present invention. In FIG. 11, a phase compensating section 26 in the present receiving apparatus includes a pilot symbol detecting section 261 for detecting a pilot symbol from a signal output from the Fourier transform section 5, and a pilot symbol detecting section 26.
A first pilot symbol phase difference calculator 262 for calculating a phase difference between the first pilot symbol output from the first pilot symbol and a predetermined reference pilot symbol, and a phase difference between pilot symbols output from the pilot symbol detector 261. Between the pilot symbol phase difference calculating section 263 for calculating the
2 and an output from the inter-pilot symbol phase difference calculating section 263 are inputted, and a phase compensation value calculating section 264 for calculating a phase compensation value, and a pilot symbol detecting section 261 based on the output from the phase compensation value calculating section 264 are used. A phase rotation unit 265 for rotating the phase of the output signal.

In FIG. 11, pilot symbol detecting section 261 detects a pilot symbol from Fourier-transformed frequency domain data, similarly to pilot symbol detecting section 61 in FIG. The first pilot symbol phase difference calculation section 262 includes a subcarrier phase included in the first pilot symbol and a reference pilot symbol stored in a memory (not shown) provided in the receiving device. The difference from the phase of the subcarrier to be obtained is obtained.

The reference pilot symbols stored in the memory are ideal pilot symbols similar to those of the receiving apparatus according to the first embodiment. Therefore, the first
By calculating the difference between the phase of the subcarrier included in the pilot symbol and the phase of the subcarrier included in the reference pilot symbol, the phase error caused by the transmission can be determined.

FIG. 12 is a schematic diagram showing subcarriers included in a first pilot symbol having a phase of φ1 and subcarriers included in a reference pilot symbol having a phase of φr. The first pilot symbol phase difference calculation section 262 calculates the phase φ1 of the subcarrier included in the first pilot symbol as shown in FIG. 12 (a) and the reception φ as shown in FIG. 12 (b). The difference φps from the phase φr of the subcarrier included in the reference pilot symbol stored in the memory on the side is calculated. The calculation formula is as shown in the following formula (5). φps (i) = φ1 (i) −φr (i) (5) where i is any integer from 1 to N.

First pilot symbol phase difference calculating section 2
62 averages the phase difference by the number of subcarriers. When the averaged value is φp, the calculation formula is
The following expression (6) is obtained.

(Equation 2)

However, the received signal is distorted by the transmission path and noise. Therefore, when obtaining φp, it is more accurate to obtain a mean value by performing weighting according to the amplitude value of each carrier of the received pilot symbol. Therefore, the calculation method will be described below.

First, the complex signal of the i-th subcarrier included in the received first pilot symbol is represented by A1 (i)
, The complex signal of the i-th subcarrier included in the received second pilot symbol is A2 (i), and the amplitude of the i-th subcarrier of the reference pilot symbol is R (i).
And Based on the above, φp is calculated by the following equation (7).

(Equation 3) Here, * in the above equation (7) represents a complex conjugate, and an
gle represents the phase angle of a complex number.

When the average value is calculated as described above, each component is weighted by the power value of A1 (i). Therefore, the phase of a carrier having a large amplitude value has a large contribution to the average value, and the phase of a carrier having a small amplitude value has a small contribution to the average value. From the above, even if the received signal is distorted by the transmission path and noise, a more accurate average value can be calculated.

Next, inter-pilot-symbol phase difference calculating section 263 obtains a phase difference between the phase of the subcarrier included in the first pilot symbol and the phase of the subcarrier included in the second pilot symbol.

FIG. 13 is a schematic diagram showing subcarriers included in a first pilot symbol having a phase of φ1 and subcarriers included in a second pilot symbol having a phase of φ2. The pilot symbol inter-symbol phase difference calculation unit 263 calculates the phase difference between pilot symbols as shown in FIG.
The phase difference φ between the phase φ1 of the subcarrier included in the first pilot symbol and the phase φ2 of the subcarrier included in the second pilot symbol as shown in FIG. 13B is calculated. The calculation formula is as shown in the following formula (8). φ (i) = φ1 (i) −φ2 (i) (8) where i is any integer from 1 to N.

Pilot-symbol phase difference calculating section 263
Averages the phase difference by the number of subcarriers. Assuming that the averaged value is φa, the calculation formula is as the following formula (9).

(Equation 4)

As described above, by averaging by the number of all subcarriers included in a pilot symbol, a phase difference can be accurately calculated over the frequencies of all subcarriers. In this regard, the phase difference can be calculated more accurately than in the conventional method of inserting a pilot carrier into each data symbol. This is because the number of pilot carriers inserted by the conventional method is extremely small compared to the number of all subcarriers, and thus the conventional method cannot accurately calculate the phase difference over the entire frequency band. is there.

In the mean value calculation method described above, as described above, it is more accurate to perform weighting according to the amplitude value of each carrier of the received pilot symbol and then calculate the mean value. Then, as described above, when the averaged value is φa, the calculation formula is as shown in the following formula (10).

(Equation 5)

When the average value is calculated as described above, since each component is weighted by the power value of A1 (i),
The phase of a carrier having a large amplitude value has a large contribution to the average value, and the phase of a carrier having a small amplitude value has a small contribution to the average value. Therefore, even if the received signal is distorted by the transmission path and noise, a more accurate average value can be calculated.

However, when the average value is calculated in this manner, it becomes impossible to calculate the compensation value individually for each subcarrier as in the receiving apparatus according to the first embodiment. However, on the other hand, when some of the subcarriers included in the pilot symbol are suppressed or lost at the time of receiving the pilot symbol, individual reception is performed as in the receiving apparatus according to the first embodiment. If the compensation value is calculated, the compensation accuracy is reduced. Therefore, the present receiving apparatus is particularly effective for frequency shift and phase noise in which all carriers receive substantially uniform distortion. Specifically, the present receiving apparatus is suitable for communication in a stationary state where transmission path distortion is small. On the other hand, the receiving apparatus according to the first embodiment is suitable for mobile communication in which transmission line distortion fluctuates in time series or time synchronization shift occurs.

Next, phase compensation value calculation section 264 calculates a phase compensation value φd for each data symbol existing between the first pilot symbol and the second pilot symbol.
Is obtained by linear approximation obtained from the phase difference φa between pilot symbols. Here, the reason for obtaining by the linear approximation is that the phase fluctuation due to the frequency shift has linearity in a time series. Therefore, according to the linear approximation, linearly accurate compensation can be performed.

FIG. 14 shows the relationship between the phase compensation value φd for each data symbol existing between the first pilot symbol and the second pilot symbol on the vertical axis and the symbol number, that is, the time, on the horizontal axis. It is a graph represented. As shown in FIG. 14, it can be seen that the phase compensation value φd for each data symbol can be obtained by linear approximation from the phase difference φa between pilot symbols.

Here, from the first pilot symbol to the second
The number of data symbols existing between pilot symbols is M, and a certain data symbol existing between the first pilot symbol and the second pilot symbol is k. Here, k is an arbitrary integer from 1 to M.
On the premise of the above, an equation for calculating the phase compensation value φd for each data symbol by the above-described linear approximation can be expressed as the following equation (11).

(Equation 6)

Next, phase rotation section 265 calculates the phase of the subcarrier included in each data symbol existing between the first pilot symbol and the second pilot symbol by the phase compensation value obtained as described above. To compensate. FIG. 15 is a schematic diagram illustrating a state of the phase compensation in the k-th data symbol. The phase of the subcarrier included in each data symbol is compensated from the obtained phase compensation value as in the following equation (12).

C′k (i) = Ck (i) × exp (j · φd (k)) (12) where i and k are any integers from 1 to N.

The above phase compensation is performed on M data symbols existing between the first pilot symbol and the second pilot symbol. Therefore, like the receiving device according to the first embodiment, actually, these data symbols are temporarily stored in a data symbol storage unit (not shown). After the phase compensation value is calculated, the data symbol stored in the data symbol storage unit is read, and the phase compensation is performed on the data symbol. Therefore, the present receiving apparatus is more suitable for a receiving system used in video transmission or broadcast-type transmission in which retransmission is not required immediately, like the receiving apparatus according to the first embodiment.

As described above, the phase compensator 26 removes the frequency shift and the residual phase error of the input data. Then, if the phase error of the data symbol between the pilot symbols is compensated for using the linear approximation, the data symbol can be accurately demodulated even in a multipath fading environment or an environment where large noise occurs. Also,
Since the phase change due to the frequency shift has linearity in the time series, it is possible to perform linear and accurate compensation. Therefore, according to the receiving apparatus or the receiving method, the effect is particularly high for a linear phase error such as a frequency shift.

As shown in the above equation (12),
In this receiving apparatus, all subcarriers included in one data symbol are phase-compensated by one phase compensation value. Therefore, compared with the transmission line frequency response compensator 6 of the receiving apparatus according to the first embodiment, which calculates the compensation value individually for each subcarrier and compensates for the frequency response fluctuation, the phase compensation of the present receiving apparatus is The unit 26 can have a simpler device configuration.

More specifically, the frequency response compensator 65 included in the transmission line frequency response compensator 6 has a built-in memory for storing compensation values corresponding to all subcarriers, and uses each compensation value. This is a configuration in which control or calculation is performed individually. On the other hand, the phase rotator 265 included in the phase compensator 26 has a built-in memory for storing only one compensation value, and is configured to control or calculate using one compensation value. A simpler device configuration can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an OFDM symbol in a transmission method according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a transmission device according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of an OFDM data symbol generation unit and an OFDM pilot symbol generation unit in the transmission device according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a receiving device according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a transmission line frequency response compensator 6 in the receiving device according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating subcarriers in a first pilot symbol and a reference symbol.

FIG. 7 is a schematic diagram illustrating subcarriers in a second pilot symbol and a reference symbol.

FIG. 8 is a diagram showing that a compensation vector can be calculated by linear approximation from the difference between the first and second pilot symbol transmission line frequency responses.

FIG. 9 is a schematic diagram illustrating frequency response fluctuation compensation for subcarriers included in a data symbol.

FIG. 10 is a block diagram illustrating a configuration of a receiving device according to a second embodiment of the present invention.

FIG. 11 is a block diagram illustrating a configuration of a phase compensating unit 26 in the receiving device according to the second embodiment of the present invention.

FIG. 12 is a schematic diagram illustrating subcarriers in a first pilot symbol and a reference symbol.

FIG. 13 is a schematic diagram illustrating subcarriers in first and second pilot symbols.

FIG. 14 is a diagram showing that a phase compensation value can be calculated by linear approximation from a phase difference between pilot symbols.

FIG. 15 is a schematic diagram illustrating phase compensation for subcarriers included in a data symbol.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 OFDM data symbol generation unit 2 OFDM pilot symbol generation unit 3 symbol selection unit 4 D / A conversion unit 5 Fourier transform unit 6 transmission line frequency response compensation unit 7 demodulation unit 11 on-axis data symbol generation unit 12 inverse Fourier transform unit 21 On-frequency pilot symbol generation unit 22 Inverse Fourier transform unit 26 Phase compensation unit 61 Pilot symbol detection unit 62 First pilot symbol transmission line frequency response calculation unit 63 Second pilot symbol transmission line frequency response calculation unit 64 Compensation vector calculation unit 65 Frequency Response compensator 261 Pilot symbol detector 262 First pilot symbol phase difference calculator 263 Inter-pilot symbol phase difference calculator 264 Phase compensation value calculator 265 Phase rotator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyoshi Shirakata 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasuo Harada 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.F-term (reference) 5K022 DD01 DD13 DD18 DD19 DD33 DD34 DD43 5K047 AA03 BB01 CC01 HH53 MM13 MM59

Claims (24)

[Claims] 1. A method of transmitting an OFDM signal from a transmission side to a reception side, wherein the OFDM signal includes a data symbol composed of data, a pilot symbol having a predetermined frequency component, an amplitude and a phase. At the transmitting side, the pilot symbol is inserted before or after one or more of the data symbols and transmitted together with the data symbol.At the receiving side, the received pilot symbol is received. A method for compensating fluctuations in the frequency response of a transmission line caused by at least one of transmission line distortion, time synchronization deviation, frequency deviation, and residual phase error of a data symbol. 2. The transmission method of an OFDM signal according to claim 1, wherein all of the subcarriers constituting the pilot symbol are pilot carriers having a predetermined amplitude and phase. 3. The O according to claim 1, wherein a plurality of the pilot symbols are continuously inserted before or after one or a plurality of the data symbols.
An FDM signal transmission method. 4. The method of claim 1, wherein the pilot symbols are periodically inserted before or after one or more of the data symbols. 5. The OFDM according to claim 1, wherein the pilot symbols are inserted aperiodically before or after one or more of the data symbols.
Signal transmission method. 6. The transmission side is characterized in that an insertion interval and an insertion number when the pilot symbol is inserted into the data symbol are adjusted so as to be adaptively changed according to a state of a transmission path. The transmission method of an OFDM signal according to claim 5. 7. The OFDM signal according to claim 5, wherein an insertion interval and an insertion number when the pilot symbol is inserted into the data symbol on the transmission side are included in the OFDM signal as control information. Signal transmission method. 8. A compensation vector calculated as a time-series linear approximation value from a difference in frequency response between closest pilot symbols is used for compensating for variation in frequency response of the transmission path, O according to claim 1
An FDM signal transmission method. 9. A method in which a value calculated as a time-series linear approximation value from a phase difference value between closest pilot symbols is used for fluctuation compensation of one or both of the frequency shift and the residual phase error. The feature of claim 1
2. The transmission method of an OFDM signal according to item 1. 10. The method according to claim 1, wherein an average value of a phase difference between pilot carriers constituting the pilot symbol is used for compensating fluctuation of a frequency response of the transmission path.
The transmission method of an OFDM signal according to claim 1. 11. The transmission method of an OFDM signal according to claim 10, wherein the average value is calculated by weighting with an amplitude value of each pilot carrier. 12. A transmitting apparatus for transmitting an OFDM signal to a receiving side, comprising: a data symbol generating unit that receives transmission data and generates an OFDM data symbol; and a pilot symbol generating unit that generates an OFDM pilot symbol. And before or after one or more of the data symbols,
An OFDM signal transmission device, comprising: a symbol selection unit that switches and outputs a signal input from the data symbol generation unit and the pilot symbol generation unit so that the pilot symbol is inserted. 13. The data symbol generation unit, to which transmission data is input, generates a data symbol on the frequency axis, generates a data symbol on the frequency axis, and performs an inverse Fourier transform on a signal from the data symbol generation unit on the frequency axis. An inverse Fourier transform unit for performing conversion, wherein the pilot symbol generation unit performs an inverse Fourier transform on a signal from the frequency axis pilot symbol generation unit that generates a pilot symbol on the frequency axis. 13. An inverse Fourier transform unit.
3. The transmission device for an OFDM signal according to claim 1. 14. A data symbol transmitted from a transmission side and constituted by data, a pilot symbol having a predetermined frequency component, an amplitude and a phase and inserted before or after one or a plurality of said data symbols. A Fourier transform unit for performing a Fourier transform on the received OFDM signal, detecting the pilot symbol from a signal output from the Fourier transform unit, and A transmission line frequency response compensator for compensating for a change in the frequency response of the transmission line with respect to the signal output from the demodulator; OF
DM signal receiving device. 15. The transmission line frequency response compensator includes: a frequency response of a pilot symbol; a frequency response of a pilot symbol closest to the pilot symbol;
And using a frequency response of a reference pilot symbol prepared on the receiving side, calculating and compensating for a compensation vector such that the frequency response of the received data symbol matches the frequency response of the reference pilot symbol. The OFDM signal receiving apparatus according to claim 14, wherein: 16. The compensation vector is calculated for all subcarriers included in the received data symbols, using all pilot carriers included in each pilot symbol. An OFDM signal receiving apparatus according to claim 15. 17. The method according to claim 1, wherein the compensation vector is calculated as a time-series linear approximation from a frequency response variation between the closest pilot symbols.
6. The receiving apparatus for an OFDM signal according to claim 5. 18. The transmission line frequency response compensator, comprising: a pilot symbol detector for detecting a first pilot symbol, which is an arbitrary pilot symbol, and a second pilot symbol transmitted after the first pilot symbol; A first pilot symbol transmission line frequency for calculating a first pilot symbol transmission line frequency response by dividing a frequency response of the first pilot symbol by a frequency response of a reference pilot symbol prepared on a receiving side; A response calculation unit, a second pilot symbol transmission line frequency response calculation unit that calculates a second pilot symbol transmission line frequency response by dividing the frequency response of the second pilot symbol by the frequency response of the reference pilot symbol And the first and second pilot symbol transmission line frequencies And a compensation vector calculation unit that receives a response vector and obtains a compensation vector for compensating for a variation in the frequency response of the transmission path. A frequency response compensation unit that receives the compensation vector and compensates the frequency response of the data symbol The receiving apparatus of an OFDM signal according to claim 14, comprising: 19. A data symbol transmitted from a transmission side and composed of data, a pilot symbol having a predetermined frequency component, amplitude and phase, and inserted before or after one or more of the data symbols A Fourier transform unit for performing a Fourier transform on the received OFDM signal, detecting the pilot symbol from a signal output from the Fourier transform unit, and performing the Fourier transform. A phase compensator for compensating for one or both of the frequency shift and the residual phase error of the signal output from the section, and a signal compensated for one or both of the frequency shift and the residual phase error, and outputting demodulated data An OFDM signal receiving device, comprising: a demodulation unit. 20. The phase compensator, using a phase difference value between a phase of a certain pilot symbol and a predetermined phase and a phase difference value between closest pilot symbols, calculates a phase of the received data symbol. 20. The OFDM signal receiving apparatus according to claim 19, wherein the apparatus calculates and compensates for a phase compensation value that matches the predetermined phase. 21. The OFDM signal receiving apparatus according to claim 20, wherein the phase difference value is calculated using an average value of phases of all pilot carriers included in each pilot symbol. 22. The OFDM signal receiving apparatus according to claim 21, wherein the average value is calculated by being weighted by an amplitude value of each of the pilot carriers. 23. The OFDM signal receiving apparatus according to claim 20, wherein the phase compensation value is calculated as a time-series linear approximation value from a phase difference value between closest pilot symbols. 24. The phase compensating unit, comprising: a pilot symbol detecting unit that detects a first pilot symbol being an arbitrary pilot symbol and a second pilot symbol transmitted after the first pilot symbol; A first pilot symbol phase difference calculator for calculating a difference between a phase of the first pilot symbol and a predetermined phase; and calculating a difference between a phase of the first pilot symbol and a phase of the second pilot symbol. A phase difference value calculated by the first pilot symbol phase difference calculation unit, and a phase difference value calculated by the pilot symbol phase difference calculation unit, A phase compensation value calculation unit for calculating a phase compensation value for correcting a residual phase error; and And a phase rotator for rotating the phase of the data symbols, the receiver of the OFDM signal according to claim 19.