JP2013187742A - Communication apparatus and communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce PAPR in OFDM system based communication and further control the degree of reduction in PAPR.SOLUTION: A sequence generation unit 12 divides any data sequence having self-correlation characteristic by a number of elements constituting an input signal to generate sub-data sequences. When the input signal satisfies a predetermined standard, a modulation unit 11 performs arithmetic to multiply each element of a sub-data sequence by an element of the input signal correlated to the sub-data sequence, or when the input signal does not satisfy a predetermined standard, it reverses the sign of each element of a sub-data sequence and the sign of an element of the input signal correlated to the sub-data sequence and performs the multiplication arithmetic. Then, it synthesizes the sub-data sequences which have undergone the arithmetic operation, arranging them at positions where they were before being divided, to generated modulation data. An IFFT unit 13 performs reverse Fast Fourier conversion on the modulation data, and a synthesis unit 14 synthesizes the result of arithmetics performed by the IFFT unit 13 to generate a data symbol. A transmission unit 15 generates a transmission frame including the data symbol and then transmits the frame via an antenna 10.

Description

  The present invention relates to a communication device and a communication method.

  In OFDM (Orthogonal Frequency-Division Multiplexing) communication, an input signal is subjected to subcarrier modulation, IFFT (Inverse Fast Fourier Transformation) is performed, and a baseband signal is generated. Therefore, when the number of subcarriers increases and the FFT (Fast Fourier Transformation) size increases, a baseband signal with a large peak is generated, and the PAPR (Peak-to-Average Power Ratio) ) Is high. As the PAPR increases, an amplifier having linearity in a wide range is required to transmit a signal without distortion. Therefore, techniques for reducing PAPR have been developed.

  In Patent Document 1, in order to reduce PAPR, the phase of the subcarrier modulation signal is controlled based on the optimum phase calculated by the sequential determination method before performing IFFT.

JP 2006-165781 A

  In OFDM communication, reducing PAPR is an issue. In Patent Document 1, it is necessary to perform iterative calculation processing in order to calculate the optimum phase for reducing the PAPR, and to control the phase for each subcarrier. Further, the technique disclosed in Patent Document 1 cannot control the degree of PAPR reduction.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce PAPR and control the degree of reduction of PAPR in OFDM communication.

In order to achieve the above object, a communication device according to the first aspect of the present invention provides:
A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
An autocorrelation value between a data series that is a set of data that is equal to or greater than the number of elements of the input signal and that has not been shifted from the data series that has been shifted in data. A sequence generation means for dividing an arbitrary data sequence having an autocorrelation characteristic higher than an autocorrelation value between them into the number of elements of the input signal to generate a subdata sequence;
When the input signal element and the sub data sequence are associated one-to-one, and the input signal satisfies a predetermined criterion, the input signal is associated with the sub data sequence to each element of the sub data sequence. The sub-data sequence subjected to the operation is combined at the position when divided by the sequence generation means to generate modulation data, and the input signal satisfies the predetermined criterion If not, the sign of each element of the sub-data series is inverted, the element of the input signal associated with the sub-data series is inverted and multiplied, and the sub-data series subjected to the calculation is calculated Modulation means for generating the modulation data by arranging and synthesizing at the position when divided by the series generation means,
IFFT means for performing inverse fast Fourier transform of the modulated data;
Combining means for combining the operation results of the IFFT means to generate a data symbol;
Transmitting means for generating and transmitting a transmission frame including the data symbols;
It is characterized by providing.

  Preferably, in the modulation means, the case where the input signal satisfies the predetermined criterion is a case where the number of elements having a value of 1 is equal to or greater than a value obtained by dividing the number of elements of the input signal by two. .

  Preferably, the sequence generation means equally divides the data sequence into the number of elements of the input signal.

  Preferably, the data series is a CAZAC (Constant Amplitude Zero Auto-Correlation) series.

The communication device according to the second aspect of the present invention is:
A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
Receiving means for receiving a transmission frame including data symbols;
FFT means for extracting the data symbols, performing serial-parallel conversion, and performing fast Fourier transform to generate a received parallel signal;
A data series that is a set of data of the same number as the number of elements of the received parallel signal, and an autocorrelation value between the same data series that is not shifted in data is a data series that is shifted in data Using a predetermined reception-side data sequence having an autocorrelation characteristic that is higher than an autocorrelation value between the reception-side data sequence and the received parallel signal or an inverse fast Fourier of the reception-side data sequence Synchronization means for detecting a synchronization position of the data symbol based on a correlation between the data symbol obtained by performing the conversion and the data symbol;
Based on the synchronization position detected by the synchronization means, the absolute value of the received parallel signal generated from the data symbol extracted by the FFT means or data obtained by parallel-serial conversion of the received parallel signal is greater than or equal to a predetermined threshold value A determination unit that replaces the value of an element with 1 and replaces the value of an element other than the element with 0 to generate post-determination data;
The post-determination data is divided into a predetermined number to generate post-determination sub-data, and each element is associated with the post-determination sub-data on a one-to-one basis, and is associated with the post-determination sub-data that satisfies a predetermined criterion. When demodulated data is generated in which the value of the element is 1 and the value of the elements other than the element is 0, and the correlation is a negative correlation, each element of the demodulated data is Demodulating means for replacing with an inverted value;
It is characterized by providing.

  Preferably, in the demodulating means, when the post-determination sub-data satisfies the predetermined criterion, the number of elements having a value of 1 is equal to or greater than a value obtained by dividing the number of elements of the post-determination sub-data by two. This is the case.

  Preferably, the demodulation means equally divides the post-determination data into the predetermined number.

  Preferably, in the determination means, the predetermined threshold value is determined for each element of the reception parallel signal, and is a value obtained by dividing an absolute value of an element at the same position as the element in the reception side data series by 2. .

  Preferably, the receiving side data series is a CAZAC (Constant Amplitude Zero Auto-Correlation) series.

The communication method according to the third aspect of the present invention is:
A communication method performed by a communication device that communicates with other devices by wireless communication of an orthogonal frequency division multiplex communication method,
An autocorrelation value between a data series that is a set of data that is equal to or greater than the number of elements of the input signal and that has not been shifted from the data series that has been shifted in data. A sequence generation step for generating a sub data sequence by dividing an arbitrary data sequence having an autocorrelation characteristic higher than an autocorrelation value between the number of elements of the input signal;
When the input signal element and the sub data sequence are associated one-to-one, and the input signal satisfies a predetermined criterion, the input signal is associated with the sub data sequence to each element of the sub data sequence. The sub-data sequence subjected to the operation is combined at the position when divided in the sequence generation step to generate modulation data, and the input signal satisfies the predetermined criterion. If not, the sign of each element of the sub-data series is inverted, the element of the input signal associated with the sub-data series is inverted and multiplied, and the sub-data series subjected to the calculation is calculated A modulation step for generating the modulation data by arranging and synthesizing at the position when divided in the sequence generation step;
An IFFT step for performing an inverse fast Fourier transform on the modulated data;
A combining step of combining the operation results of the IFFT step to generate a data symbol;
Generating and transmitting a transmission frame including the data symbols;
It is characterized by providing.

A communication method according to a fourth aspect of the present invention is:
A communication method performed by a communication device that communicates with other devices by wireless communication of an orthogonal frequency division multiplex communication method,
A receiving step for receiving a transmission frame including data symbols;
An FFT step of extracting the data symbols and performing serial-parallel conversion and performing fast Fourier transform to generate a received parallel signal;
A data series that is a set of data of the same number as the number of elements of the received parallel signal, and an autocorrelation value between the same data series that is not shifted in data is a data series that is shifted in data Using a predetermined reception-side data sequence having an autocorrelation characteristic that is higher than an autocorrelation value between the reception-side data sequence and the received parallel signal or an inverse fast Fourier of the reception-side data sequence A synchronization step of detecting a synchronization position of the data symbol based on a correlation between the data symbol obtained by performing the transformation and the data symbol;
Based on the synchronization position detected in the synchronization step, the absolute value of the received parallel signal generated from the data symbol extracted in the FFT step or data obtained by parallel-serial conversion of the received parallel signal is greater than or equal to a predetermined threshold value A determination step of replacing the value of an element with 1 and replacing the value of an element other than the element with 0 to generate post-determination data;
The post-determination data is divided into a predetermined number to generate post-determination sub-data, and each element is associated with the post-determination sub-data on a one-to-one basis, and is associated with the post-determination sub-data that satisfies a predetermined criterion. When demodulated data is generated in which the value of the element is 1 and the value of the elements other than the element is 0, and the correlation is a negative correlation, each element of the demodulated data is A demodulation step that replaces with an inverted value;
It is characterized by providing.

  According to the present invention, it is possible to reduce PAPR and further control the degree of PAPR reduction in OFDM communication.

It is a block diagram which shows the structural example of the communication apparatus which concerns on embodiment of this invention. It is a block diagram which shows the example of a different structure of the communication apparatus which concerns on embodiment. It is a figure which shows the modulation process which the communication apparatus which concerns on embodiment performs. It is a flowchart which shows an example of the operation | movement of transmission control which the communication apparatus which concerns on embodiment performs. It is a figure which shows the determination process and demodulation process which the communication apparatus which concerns on embodiment performs. It is a flowchart which shows an example of the operation | movement of reception control which the communication apparatus which concerns on embodiment performs. It is a figure which shows the CCDF characteristic of PAPR of the simulated baseband signal. It is the signal point arrangement | positioning figure of the calculation result of the IFFT part simulated. It is the signal point arrangement | positioning figure of the calculation result of the IFFT part simulated. It is a block diagram which shows the example of a different structure of the communication apparatus which concerns on embodiment. It is a flowchart which shows another example of the operation | movement of reception control which the communication apparatus which concerns on embodiment performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent parts are denoted by the same reference numerals. In the following description, IFFT (Inverse Fast Fourier Transformation) is a concept including IFFT and IDFT (Inverse Discrete Fourier Transformation). Therefore, in the embodiment of the present invention, IDFT may be performed instead of IFFT. Similarly, FFT (Fast Fourier Transformation) is a concept including FFT and DFT (Discrete Fourier Transformation). When performing IDFT and DFT, the FFT size in the following description means the size of the DFT.

  FIG. 1 is a block diagram illustrating a configuration example of a communication device according to an embodiment of the present invention. The communication device 1 communicates with other devices by OFDM (Orthogonal Frequency-Division Multiplexing) wireless communication. The communication device 1 includes an antenna 10, a modulation unit 11, a sequence generation unit 12, an IFFT unit 13, a synthesis unit 14, a transmission unit 15, and a controller 20.

  The controller 20 includes a CPU (Central Processing Unit) 21, a RAM (Random Access Memory) 23, and a ROM (Read-Only Memory) 24. In order to avoid complication and to facilitate understanding, signal lines from the controller 20 to each part are omitted, but the controller 20 is connected to each part of the communication device 1 via an I / O (Input / Output) 22. The start and end of these processes and the control of the process contents are performed.

  In the RAM 23, for example, data for generating a transmission frame is stored. The ROM 24 stores a control program for the controller 20 to control the operation of the communication device 1. The controller 20 controls the communication device 1 based on the control program.

  FIG. 2 is a block diagram illustrating a different configuration example of the communication device according to the embodiment. In order to provide the above-described communication device 1 with a reception function, the communication device 1 illustrated in FIG. 2 further includes a demodulation unit 31, a determination unit 32, a synchronization unit 33, a sequence generation unit 34, an FFT unit 35, a reception unit 36, and a transmission / reception switching unit. 37. A communication method performed by the communication device 1 using the communication device 1 shown in FIG. 2 having a transmission function and a reception function will be described below.

  The sequence generation unit 12 is a data sequence that is a set of data equal to or greater than the number of elements of the input signal, and divides an arbitrary data sequence having autocorrelation characteristics into the number of elements of the input signal to generate a sub-data sequence Is generated. An autocorrelation value between an arbitrary data series having autocorrelation characteristics and the same data series that has not undergone data shift is compared to an autocorrelation value between data series that has undergone arbitrary data shift High data series. A data series that has undergone an arbitrary shift of data differs in the value of at least one element from a data series that has not undergone a data shift. As such a data series, for example, a CAZAC (Constant Amplitude Zero Auto-Correlation) series can be used. If the number of elements of the CAZAC sequence is, for example, a natural number multiple of the number M of elements of the input signal, the number N of elements of the CAZAC sequence can be expressed by the following equation (1). It is assumed that the sequence generation unit 12 holds information about the number of elements of the input signal in advance.

  The CAZAC sequence is represented by the following equation (2), and each element of the CAZAC sequence is represented by the following equation (3).

The sequence generation unit 12 divides the CAZAC sequence into the number of elements of the input signal and generates sub data sequences b ₀ , b ₁ ,..., B _M−1 as represented by the following equation (4). To do. The number of elements in the CAZAC sequence does not have to be a natural multiple of the number of elements in the input signal, and the number of elements in each subdata series may not be the same, but the number of elements in each subdata series is the same. As described above, if the CAZAC sequence is equally divided by the sequence generation unit 12, the implementation of the processing of the modulation unit 11 can be simplified.

Modulation section 11 associates the elements of the input signal with the sub data series on a one-to-one basis. The input signal d is expressed by the following equation (5). The value of each element of the input signal d is 0 or 1. In the following equation (5), the input signal d is represented by a column vector. However, the input signal d may be a serial signal or a parallel signal generated by serial-parallel conversion of the serial signal. Also good. For example, the modulation unit 11 associates d ₀ and b ₀ , d ₁ and b ₁ ,..., D _M−1 and b _M−1.

When the input signal satisfies a predetermined standard, the modulation unit 11 multiplies each element of the sub data series by the element of the input signal associated with the sub data series, and sets the position when the sub data series is divided. Modulated data is generated by combining them side by side. The case where the input signal satisfies a predetermined criterion is, for example, a case where the number of elements whose value is 1 is equal to or greater than the value obtained by dividing the number of elements of the input signal by 2. When the input signal satisfies a predetermined criterion, the modulation unit 11 multiplies each element of the sub data series b ₀ by the element d ₀ of the input signal associated with the sub data series. The sub data series b ′ ₀ subjected to the above calculation is expressed by the following equation (6). Sub-data sequence b sub data sequence b was subjected to the above calculation in _{1 M-1 '1,} and the sub-data sequence b sub data sequence b was subjected to the above calculation to _M-1', respectively (7) below, It is represented by the formula (8).

  As represented by the following equation (9), the modulation unit 11 generates modulated data by arranging and synthesizing the sub-data series subjected to the above-described calculation at the positions when the series generation unit 12 divides.

When the input signal does not satisfy a predetermined criterion, the modulation unit 11 inverts the sign of each element of the sub data sequence, inverts and multiplies the element of the input signal associated with the sub data sequence, Modulated data is generated by arranging and synthesizing the data series at the position when the data series is divided. Inversion of an input signal element means that an element having a value of 0 is replaced with 1, and an element having a value of 1 is replaced with 0. Modulator 11, when the input signal does not satisfy a predetermined criterion, by inverting the sign of each element of the sub-data sequence b _0, and inverts the element d ₀ of the input signal associated to the sub-data sequence multiplying To do. The sub data series b ′ ₀ subjected to the above calculation is represented by the following equation (10). D Upperlines below (10) wherein is attached ₀ is a value obtained by inverting the d _0.

  The modulation unit 11 performs the above-described calculation in the same manner for the other sub-data series, and generates the modulation data by arranging and synthesizing the sub-data series subjected to the above-mentioned calculation at the position when the sequence generation unit 12 divides it. To do. The modulation unit 11 sends the modulated data to the IFFT unit 13.

  The predetermined criterion is not limited to the above-described criterion. For example, a case where the value of at least one element among the elements of the input signal is 1 may be a case where the predetermined criterion is satisfied.

  The IFFT unit 13 performs IFFT of the modulation data and sends the calculation result to the synthesis unit 14. The synthesizer 14 synthesizes the operation results of the IFFT unit 13 to generate a data symbol and sends it to the transmitter 15. The transmission unit 15 generates a transmission frame including data symbols and transmits the transmission frame to other devices via the transmission / reception switching unit 37 and the antenna 10.

FIG. 3 is a diagram illustrating a modulation process performed by the communication device according to the embodiment. The horizontal axis is the element, and the vertical axis is the absolute value of the element. Since each element of the CAZAC sequence is a complex number, display is simplified using the absolute value of the element. The input signal satisfies a predetermined standard, the number of elements of the input signal is M = 8, and a = 2 in the above equation (1). 3A shows an input signal, FIG. 3B shows a CAZAC sequence, and FIG. 3C shows modulation data. Two elements c _{0 to} c ₁₅ of the CAZAC sequence are associated with each element of the input signal 11010010. The above-described calculation is performed when the input signal satisfies a predetermined standard, and modulation data having an absolute value as shown in FIG. 3C is generated. Since the value of the element of the modulation data is determined based on the input signal, the input signal can be restored on the receiving side as will be described later.

  FIG. 4 is a flowchart illustrating an example of a transmission control operation performed by the communication device according to the embodiment. The sequence generation unit 12 divides an arbitrary data sequence having autocorrelation characteristics into the number of elements of the input signal and generates a sub data sequence (step S110). Modulation section 11 associates the elements of the input signal with the sub data series on a one-to-one basis (step S120). When the input signal satisfies a predetermined criterion (step S130: Y), the modulation unit 11 multiplies each element of the sub data series by the element of the input signal associated with the sub data series (step S140).

  When the input signal does not satisfy the predetermined standard (step S130: N), the modulation unit 11 inverts the sign of each element of the sub data series and inverts the element of the input signal associated with the sub data series And multiply (step S150). The modulation unit 11 generates modulation data by arranging the sub-data series calculated in steps S140 and S150 at the positions when they are divided by the series generation unit 12 and synthesizing them (step S160).

  The IFFT unit 13 performs IFFT of the modulation data (step S170). The synthesizer 14 synthesizes the calculation result of the IFFT unit 13 to generate a data symbol (step S180). The transmission unit 15 generates and transmits a transmission frame including data symbols (step S190). When the transmission process in step S190 is completed, the process ends.

  Processing on the receiving side will be described below. The receiving unit 36 receives a transmission frame including a data symbol via the antenna 10 and the transmission / reception switching unit 37 and sends it to the FFT unit 35. The FFT unit 35 extracts data symbols and performs serial-parallel conversion, and performs FFT to generate a received parallel signal. The sequence generation unit 34 generates a predetermined reception-side data sequence having a self-correlation characteristic, which is a data sequence that is a set of data of the same number as the number of elements of the received parallel signal, and sends it to the synchronization unit 33. A data sequence having autocorrelation characteristics is a data sequence in which the autocorrelation value with the same data sequence without data shift is higher than the autocorrelation value with the data sequence with data shift It is. The predetermined receiving side data series is the same data series as the data series used in the series generation unit 12.

  The synchronization unit 33 performs correlation analysis between the reception-side data series and the reception parallel signal, detects the presence or absence of correlation, and detects the synchronization position of the data symbol. If the correlation cannot be detected, the synchronization unit 33 notifies the FFT unit 35 that there is no correlation, and the FFT unit 35 performs the serial / parallel conversion of the data symbols at different timings for extracting the data symbols, and performs the FFT. And the synchronization unit 33 repeats the correlation analysis. When a positive correlation or a negative correlation is detected, the synchronization unit 33 sends to the determination unit 32 that the received parallel signal and the positive correlation or the negative correlation that have been synchronized are detected.

  The determination unit 32 performs the following processing based on the received parallel signal synchronized by the synchronization unit 33. The determination unit 32 replaces the value of an element whose absolute value is equal to or greater than a predetermined threshold with respect to the received parallel signal or the data obtained by parallel-serial conversion of the received parallel signal, and replaces the values of elements other than the element with 0. Generate post-determination data. The predetermined threshold is determined for each element of the received parallel signal, for example, and a value obtained by dividing the absolute value of the element at the same position as the element in the reception side data series by two is used. Moreover, you may comprise so that the real number other than the value which divided the absolute value of the element of the receiving side data series by 2 may be used as a predetermined threshold value.

  The reception parallel signal r matches the modulation data represented by the above equation (9) generated by the modulation unit 11. The post-determination data s generated by replacing the value of an element whose absolute value is equal to or greater than a predetermined threshold with 1 and replacing the value of an element other than the element with 0 is expressed by the following equation (11).

  The determination unit 32 may be configured to perform the above-described calculation on data obtained by parallel-serial conversion of the received parallel signal. In that case, the post-determination data s is a serial signal represented by the transposed matrix of the above equation (11). The determination unit 32 sends to the demodulation unit 31 that the post-determination sub-data and the synchronization unit 33 have detected a positive correlation or a negative correlation.

The demodulator 31 divides the post-determination data into a predetermined number and generates post-determination sub-data. The predetermined number is the number of sub-data sequences generated by dividing the data sequence by the sequence generation unit 12, and the demodulating unit 31 determines the post-determination data in the same manner as the method of dividing the data sequence by the sequence generation unit 12. To generate post-determination sub-data. The demodulator 31 divides the post-determination data s as represented by the following equation (12) to generate post-determination sub-data t ₀ , t ₁ ,..., T _M−1 . Each element of the decision after the sub data t ₀ is expressed by the following equation (13). In the following formulas (12) and (13), the post-determination sub-data is represented by using a column vector. The post-determination sub-data is a serial signal represented by the transposed matrix of the following equations (12) and (13).

  When the demodulator 31 detects a positive correlation in the synchronization unit 33, each element is associated with the determined sub-data on a one-to-one basis, and is associated with the determined sub-data satisfying a predetermined criterion The demodulated data is generated with the value of 1 being 1 and the values of elements other than the element being 0. The case where the predetermined criterion is satisfied is, for example, a case where the number of elements whose value is 1 is equal to or greater than the value obtained by dividing the number of elements of the post-determination subdata by 2.

  When the demodulator 31 detects a negative correlation in the synchronizer 33, each element is associated with the determined sub-data on a one-to-one basis, and is associated with the determined sub-data satisfying a predetermined criterion. Is generated, demodulated data having a value of 0 other than the element is generated, and each element of the demodulated data is replaced with a value obtained by inverting the element.

  The post-demodulation data u generated by the demodulator 31 represented by the following equation (14) matches the input signal d. In the following equation (14), the demodulated data is represented by a column vector, but the demodulated data may be a serial signal. If the demodulated data is a parallel signal, parallel-to-serial conversion may be performed and the serial signal may be sent to another device.

  FIG. 5 is a diagram illustrating determination processing and demodulation processing performed by the communication device according to the embodiment. Assume that the receiving side has received a transmission frame including a data symbol based on the modulation data generated by performing the modulation processing shown in FIG. 3, and the synchronization unit 33 has detected a positive correlation. The horizontal axis represents the element, the vertical axis represents the absolute value of the element, and the dotted line represents the threshold value. FIG. 5A shows a received parallel signal synchronized by the synchronization unit 33 or data obtained by parallel-serial conversion of the received parallel signal. The signal shown in FIG. 5A is affected by noise, and has an absolute value different from that of the modulation data shown in FIG. FIG. 5B shows post-determination data generated with the value of an element whose absolute value is equal to or greater than the threshold being 1 and the value of the other elements being 0. FIG. 5C divides the post-determination data into post-determination sub-data including two elements, and if the number of elements having a value of 1 is 1 or more, the element associated with the post-determination sub-data The demodulated data is generated with a value of 1 and 0 otherwise. The post-return data matches the input signal shown in FIG. 3A, and it can be seen that the input signal can be restored on the receiving side.

  FIG. 6 is a flowchart illustrating an example of a reception control operation performed by the communication device according to the embodiment. The receiving unit 36 receives a transmission frame including a data symbol via the antenna 10 and the transmission / reception switching unit 37 (step S210). The FFT unit 35 extracts data symbols and performs serial-parallel conversion, and performs FFT to generate a received parallel signal (step S220). The synchronization unit 33 performs correlation analysis between the reception-side data series and the reception parallel signal (step S230). When the correlation is not detected (step S240: N), the fact is notified to the FFT unit 35, and the process returns to step S220, where the FFT unit 35 changes the timing for extracting the data symbol and changes the data symbol directly. Parallel conversion is performed, FFT is performed, and the synchronization unit 33 repeatedly performs correlation analysis.

  When a positive correlation or a negative correlation is detected (step S240: Y), the determination unit 32 uses the absolute value of the received parallel signal synchronized by the synchronization unit 33 or the data obtained by parallel-serial conversion of the received parallel signal. The value of an element whose value is equal to or greater than a predetermined threshold is replaced with 1, and the value of an element other than the element is replaced with 0 to generate post-determination data (step S250). The demodulator 31 divides the post-determination data into a predetermined number and generates post-determination sub-data (step S260). In the demodulator 31, each element is associated with the determined sub-data on a one-to-one basis, the value of the element corresponding to the determined sub-data satisfying a predetermined criterion is 1, and the values of elements other than the element are Data after demodulation that is 0 is generated (step S270). In step S230, when the synchronization unit 33 detects a positive correlation (step 280: Y), the process ends without performing the process of step S290. If the synchronization unit 33 detects a negative correlation in step S230 (step S280: N), each element of the demodulated data generated in step S270 is replaced with a value obtained by inverting the element (step S290). When the process of step S290 is completed, the process ends.

  In accordance with the principle described above, the communication device 1 performs communication as follows, for example. Assume that the number of elements of the input signal is 4, and the input signal d is expressed by the following equation (15).

  Assuming that a = 4 in the above equation (1), the sequence generation unit 12 divides the data sequence represented by the following equation (16) into four equal parts to generate a sub data sequence and sends it to the modulation unit 11. The subscript T indicates that the matrix is transposed. Each element of the data series is expressed by the above equation (3), and N = 16.

When the input signal satisfies a predetermined criterion is when the number of elements having a value of 1 is equal to or greater than the value obtained by dividing the number of elements of the input signal by 2, the input signal of the above equation (15) is Meet the standards. The modulation unit 11 multiplies each element of the sub data sequence b ₀ by the element d ₀ of the input signal associated with the sub data sequence. The sub data series b ′ ₀ subjected to the above calculation is represented by the following equation (17).

The sub-data sequence b in the sub-data sequence b ₁ was subjected to the above calculation _{2 '1,} sub-data sequence b was subjected to the above calculation in the sub-data sequence b _2', and the sub-data sequence b ₃ the operation of the above The applied sub data series b ′ ₃ is expressed by the following equations (18), (19), and (20), respectively.

  The modulation unit 11 generates modulated data by arranging and synthesizing the sub-data series subjected to the above calculation at the position when the series generation unit 12 divides it. The modulation data b ′ is expressed by the following equation (21).

  The IFFT unit 13 performs IFFT of the modulation data and sends the calculation result to the synthesis unit 14. The synthesizer 14 synthesizes the operation results of the IFFT unit 13 to generate a data symbol and sends it to the transmitter 15. The transmission unit 15 generates a transmission frame including data symbols and transmits the transmission frame to other devices via the transmission / reception switching unit 37 and the antenna 10.

  The receiving unit 36 receives a transmission frame including a data symbol via the antenna 10 and the transmission / reception switching unit 37 and sends it to the FFT unit 35. The FFT unit 35 performs serial-parallel conversion on the data symbols and performs FFT to generate a received parallel signal. The sequence generation unit 34 generates the reception side data sequence represented by the above equation (16) and sends it to the synchronization unit 33. Each element of the receiving data series is expressed by the above equation (3).

  The synchronization unit 33 performs correlation analysis between the reception-side data series and the reception parallel signal, and detects the presence or absence of the correlation. If the correlation cannot be detected, the synchronization unit 33 notifies the FFT unit 35 that there is no correlation, and the FFT unit 35 performs the serial / parallel conversion of the data symbols at different timings for extracting the data symbols, and performs the FFT. And the synchronization unit 33 repeats the correlation analysis. When a positive correlation or a negative correlation is detected, the synchronization unit 33 sends to the determination unit 32 that the received parallel signal and the positive correlation or the negative correlation that have been synchronized are detected. In this case, the synchronization unit 33 detects a positive correlation.

  The determination unit 32 performs the following processing based on the received parallel signal synchronized by the synchronization unit 33. The determination unit 32 sets the value of an element whose absolute value is equal to or greater than a predetermined threshold to 1 for a received parallel signal that matches the modulation data represented by the above equation (21) or data obtained by parallel-serial conversion of the received parallel signal. The data after determination is generated by replacing the values of elements other than the element with 0. The predetermined threshold is determined for each element of the received parallel signal, as expressed by the following equation (22), and a value obtained by dividing the absolute value of the element at the same position as the element in the receiving side data series by two: Use.

  The post-determination data s generated by replacing the value of an element whose absolute value is equal to or greater than a predetermined threshold with 1 and replacing the value of an element other than the element with 0 is expressed by the following equation (23).

The demodulator 31 divides the post-determination data into four equal parts to generate post-determination sub-data t ₀ , t ₁ , t ₂ , t ₃ . Determining after the sub data _{t 0} is expressed by the following equation (24).

Since the demodulator 31 detects a positive correlation in the synchronizer 33, each element is associated with the determined sub-data on a one-to-one basis, and the value of the element corresponding to the determined sub-data satisfying a predetermined criterion 1 is generated, and post-demodulation data in which the value of an element other than the element is 0 is generated. Demodulation and if they meet a predetermined criterion, the value is the number of elements that are 1 is that it is the case the number of elements in the sub-data after the determination is divided by a value more than 2, which associates the determination after the sub data t ₀ The element of the post data is 1. If the element value of the demodulated data is similarly determined based on the other post-determination sub-data, the demodulated data is expressed by the following equation (25).

  It can be seen that the input signal can be restored on the receiving side by the above processing. Next, an input signal d represented by the following equation (26) having four elements is used.

The sequence generation unit 12 divides the data sequence represented by the above equation (16) into four equal parts to generate a sub data sequence and sends it to the modulation unit 11. Each element of the data series is expressed by the above equation (3). The case where the input signal satisfies a predetermined standard is the case where the number of elements having a value of 1 is equal to or greater than the value obtained by dividing the number of elements of the input signal by 2; The signal does not meet the predetermined criteria. Modulation unit 11 inverts the sign of each element of the sub-data sequence b _0, multiplied by inverting the elements d ₀ of the input signal associated to the sub-data sequence. The sub data series b ′ ₀ subjected to the above calculation is expressed by the following equation (27).

The sub-data sequence b in the sub-data sequence b ₁ was subjected to the above calculation _{2 '1,} sub-data sequence b was subjected to the above calculation in the sub-data sequence b _2', and the sub-data sequence b ₃ the operation of the above The post-computation sub-data series b ′ _{3 applied} is expressed by the following equations (28), (29), and (30), respectively.

  The modulation unit 11 generates modulated data by arranging and synthesizing the sub-data series subjected to the above calculation at the position when the series generation unit 12 divides it. The modulation data b 'is expressed by the following equation (31).

  The IFFT unit 13 performs IFFT of the modulation data and sends the calculation result to the synthesis unit 14. The synthesizer 14 synthesizes the operation results of the IFFT unit 13 to generate a data symbol and sends it to the transmitter 15. The transmission unit 15 generates a transmission frame including data symbols and transmits the transmission frame to other devices via the transmission / reception switching unit 37 and the antenna 10.

  The receiving unit 36 receives a transmission frame including a data symbol via the antenna 10 and the transmission / reception switching unit 37 and sends it to the FFT unit 35. The FFT unit 35 extracts data symbols and performs serial-parallel conversion, and performs FFT to generate a received parallel signal. The sequence generation unit 34 generates the reception side data sequence represented by the above equation (16) and sends it to the synchronization unit 33. Each element of the receiving data series is expressed by the above equation (3).

  The synchronization unit 33 performs correlation analysis between the reception-side data series and the reception parallel signal, and detects the presence or absence of the correlation. If the correlation cannot be detected, the synchronization unit 33 notifies the FFT unit 35 that there is no correlation, and the FFT unit 35 performs the serial / parallel conversion of the data symbols at different timings for extracting the data symbols, and performs the FFT. And the synchronization unit 33 repeats the correlation analysis. When a positive correlation or a negative correlation is detected, the synchronization unit 33 sends to the determination unit 32 that the received parallel signal and the positive correlation or the negative correlation that have been synchronized are detected. In this case, the synchronization unit 33 detects a negative correlation.

  The determination unit 32 performs the following processing based on the received parallel signal synchronized by the synchronization unit 33. The determination unit 32 sets the value of an element whose absolute value is equal to or greater than a predetermined threshold to 1 for a received parallel signal that matches the modulated data represented by the above equation (31) or data obtained by parallel-serial conversion of the received parallel signal. The data after determination is generated by replacing the values of elements other than the element with 0. The predetermined threshold is determined for each element of the received parallel signal as expressed by the above equation (22), and a value obtained by dividing the absolute value of the element at the same position as the element in the receiving side data series by two. Use.

  The post-determination data s generated by replacing the value of an element whose absolute value is equal to or greater than a predetermined threshold with 1 and replacing the value of an element other than the element with 0 is expressed by the following equation (32).

The demodulator 31 divides the post-determination data into four equal parts to generate post-determination sub-data t ₀ , t ₁ , t ₂ , t ₃ . Determining after the sub data _{t 0} is represented by the equation (24).

Since the demodulator 31 has detected a negative correlation in the synchronization unit 33, each element is associated with the determined sub-data on a one-to-one basis, and the value of the element associated with the determined sub-data satisfying a predetermined criterion Is generated, demodulated data in which the values of elements other than the element are 0, and each element of the demodulated data is replaced with a value obtained by inverting the element. Demodulation and if they meet a predetermined criterion, the value is the number of elements that are 1 is that it is the case the number of elements in the sub-data after the determination is divided by a value more than 2, which associates the determination after the sub data t ₀ The element of the subsequent data is 1, and the value obtained by inverting the element is 0. If the value of an element of demodulated data is similarly determined based on other post-determination sub-data and replaced with a value obtained by inverting the element, the demodulated data is expressed by the following equation (33). It can be seen that the input signal can be restored on the receiving side by the above processing.

  As described above, according to the communication device 1 according to the embodiment of the present invention, in the OFDM communication system, a predetermined calculation is performed on a data sequence based on an input signal to generate a baseband signal, thereby reducing PAPR. It becomes possible. As will be described later, it is possible to reduce PAPR and control the degree of reduction of PAPR.

(Concrete example)
Next, the effect of the invention according to the present embodiment will be described by simulation. Using a random signal as an input signal, a simulation was performed for generating data symbols and repeatedly calculating PAPR for the related art and the invention according to the present embodiment. The number of elements of the input signal is set to 64, and the characteristics of the PAPR CCDF (Complementary Cumulative Distribution Function) of the invention according to the present embodiment, that is, the PAPR occurrence probability, are compared. In the conventional technology, the modulation signal obtained by modulating the input signal with QPSK (Quadrature Phase-Shift Keying) is serial-parallel converted and assigned to subcarriers whose frequency components are orthogonal to each other to generate a subcarrier modulation signal. did. Then, IFFT of the subcarrier modulation signal is performed and combined to generate a data symbol. The FFT size was 32.

  FIG. 7 is a diagram showing the PAPR CCDF characteristics of the simulated baseband signal. The horizontal axis is PAPR (unit: dB), and the vertical axis is PAPR CCDF. In this embodiment, a CAZAC sequence in which each element is represented by the above equation (3) is used, and a simulation is performed by changing a in the above equation (1). 7A, 7B, and 7C, the CCDF characteristics of the conventional PAPR are solid line graphs. In FIG. 7A, in the present embodiment, a = 1 is a thin solid line graph, a = 2 is a dotted line graph, and a = 4 is a one-dot chain line graph. . In FIG. 7B, in the present embodiment, a = 8 is a thin solid line graph, a = 16 is a dotted line graph, and a = 32 is a one-dot chain line graph. . In FIG. 7C, in the present embodiment, a = 64 is a thin solid line graph, a = 128 is a dotted line graph, and a = 256 is a one-dot chain line graph. . It can be seen that the degree of PAPR reduction is improved as a is increased.

  8 and 9 are signal point arrangement diagrams of the simulation result of the IFFT unit. With respect to the present embodiment, a simulation was performed in which IFFT was performed by using a certain random signal, changing a in the above equation (1), performing a calculation based on the input signal to the data series. 8A is a signal point arrangement diagram when a = 1, FIG. 8B is a signal point arrangement diagram when a = 2, and FIG. 8C is a case where a = 4. FIG. 8D is a signal point arrangement diagram when a = 8, FIG. 8E is a signal point arrangement diagram when a = 16, and FIG. 9 is a signal point arrangement diagram when a = 32, FIG. 9A is a signal point arrangement diagram when a = 64, and FIG. 9B is a signal point arrangement diagram when a = 128. FIG. 9C is a signal point arrangement diagram when a = 256. It can be seen that as a is increased, the point on the complex plane corresponding to the calculation result of the IFFT unit 13 is located in a circle centered on the origin of the complex plane.

  From the above simulation, it has been found that in the present embodiment, PAPR can be reduced by performing a predetermined calculation on the data series based on the input signal and generating a baseband signal. It was also found that the degree of PAPR reduction can be controlled by changing the number of elements in the data series.

  The embodiment of the present invention is not limited to the above-described embodiment. FIG. 10 is a diagram illustrating a different configuration example of the communication device according to the embodiment. In addition to the configuration of the communication device 1 illustrated in FIG. 2, an IFFT unit 38 is provided. Processing on the receiving side different from the above-described embodiment will be described. The sequence generation unit 34 generates a reception side data sequence and sends it to the IFFT unit 38. The IFFT unit 38 sends the synthesized data by performing the IFFT of the receiving side data series to the synchronization unit 33. The synchronization unit 33 detects the synchronization position of the data symbol based on the correlation between the data symbol and the data synthesized by performing the IFFT of the receiving side data series, and obtains the synchronized data symbol and the positive correlation or the negative correlation. The fact that it has been detected is sent to the FFT unit 35. The FFT unit 35 performs serial-parallel conversion and FFT on the data symbols synchronized by the synchronization unit 33, and sends to the determination unit 32 that a positive correlation or a negative correlation has been detected by the received parallel signal and the synchronization unit 33.

  FIG. 11 is a flowchart illustrating another example of the reception control operation performed by the communication device according to the embodiment. Step S210 is the same as the reception control operation shown in FIG. The synchronization unit 33 detects the synchronization position of the data symbol based on the correlation between the data and the data symbol synthesized by performing the IFFT of the reception side data series (step S211). The FFT unit 35 performs serial / parallel conversion and FFT on the data symbols (step S220). The subsequent steps S250 to S290 are the same as the reception control operation shown in FIG.

  The processing of the sequence generation unit 12 may be performed by the modulation unit 11. The IFFT units 13 and 38 may be configured to perform IDFT instead of IFFT, and the FFT unit 35 may be configured to perform DFT instead of FFT. The sequence generation unit 12 can use a PN (Pseudorandom Noise) sequence or the like in addition to the CAZAC sequence. For parallel-serial conversion on the receiving side, the determination unit 32 may perform parallel-serial conversion of the received parallel signal, or the demodulation unit 31 generates post-demodulation data that is a parallel signal, and parallel-serial conversion of the demodulated data May be performed.

1 communication equipment
10 Antenna
11 Modulator
12 series generator
13 IFFT section
14 Synthesizer
15 Transmitter
20 controller
21 CPU
22 I / O
23 RAM
24 ROM
31 Demodulator
32 judgment part
33 Synchronization part
34 Series generator
35 FFT section
36 Receiver
37 Transmission / reception switching unit
38 IFFT section

Claims (11)

A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
An autocorrelation value between a data series that is a set of data that is equal to or greater than the number of elements of the input signal and that has not been shifted from the data series that has been shifted in data. A sequence generation means for dividing an arbitrary data sequence having an autocorrelation characteristic higher than an autocorrelation value between them into the number of elements of the input signal to generate a subdata sequence;
When the input signal element and the sub data sequence are associated one-to-one, and the input signal satisfies a predetermined criterion, the input signal is associated with the sub data sequence to each element of the sub data sequence. The sub-data sequence subjected to the operation is combined at the position when divided by the sequence generation means to generate modulation data, and the input signal satisfies the predetermined criterion If not, the sign of each element of the sub-data series is inverted, the element of the input signal associated with the sub-data series is inverted and multiplied, and the sub-data series subjected to the calculation is calculated Modulation means for generating the modulation data by arranging and synthesizing at the position when divided by the series generation means,
IFFT means for performing inverse fast Fourier transform of the modulated data;
Combining means for combining the operation results of the IFFT means to generate a data symbol;
Transmitting means for generating and transmitting a transmission frame including the data symbols;
A communication device comprising:   In the modulation means, the case where the input signal satisfies the predetermined criterion is a case where the number of elements having a value of 1 is equal to or greater than a value obtained by dividing the number of elements of the input signal by two. The communication device according to claim 1.   The communication device according to claim 1, wherein the sequence generation unit equally divides the data sequence into the number of elements of the input signal.   4. The communication device according to claim 1, wherein the data series is a CAZAC (Constant Amplitude Zero Auto-Correlation) series. A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
Receiving means for receiving a transmission frame including data symbols;
FFT means for extracting the data symbols, performing serial-parallel conversion, and performing fast Fourier transform to generate a received parallel signal;
A data series that is a set of data of the same number as the number of elements of the received parallel signal, and an autocorrelation value between the same data series that is not shifted in data is a data series that is shifted in data Using a predetermined reception-side data sequence having an autocorrelation characteristic that is higher than an autocorrelation value between the reception-side data sequence and the received parallel signal or an inverse fast Fourier of the reception-side data sequence Synchronization means for detecting a synchronization position of the data symbol based on a correlation between the data symbol obtained by performing the conversion and the data symbol;
Based on the synchronization position detected by the synchronization means, the absolute value of the received parallel signal generated from the data symbol extracted by the FFT means or data obtained by parallel-serial conversion of the received parallel signal is greater than or equal to a predetermined threshold value A determination unit that replaces the value of an element with 1 and replaces the value of an element other than the element with 0 to generate post-determination data;
The post-determination data is divided into a predetermined number to generate post-determination sub-data, and each element is associated with the post-determination sub-data on a one-to-one basis, and is associated with the post-determination sub-data that satisfies a predetermined criterion. When demodulated data is generated in which the value of the element is 1 and the value of the elements other than the element is 0, and the correlation is a negative correlation, each element of the demodulated data is Demodulating means for replacing with an inverted value;
A communication device comprising:   In the demodulating means, the case where the post-determination sub-data satisfies the predetermined criterion is a case where the number of elements whose value is 1 is equal to or greater than a value obtained by dividing the number of elements of the post-determination sub-data by 2. The communication apparatus according to claim 5, wherein the communication apparatus is provided.   7. The communication apparatus according to claim 5, wherein the demodulating unit equally divides the post-determination data into the predetermined number.   In the determining means, the predetermined threshold value is determined for each element of the received parallel signal, and is a value obtained by dividing by 2 an absolute value of an element at the same position as the element in the receiving side data series. The communication device according to any one of claims 5 to 7.   9. The communication apparatus according to claim 5, wherein the reception-side data series is a CAZAC (Constant Amplitude Zero Auto-Correlation) series. A communication method performed by a communication device that communicates with other devices by wireless communication of an orthogonal frequency division multiplex communication method,
An autocorrelation value between a data series that is a set of data that is equal to or greater than the number of elements of the input signal and that has not been shifted from the data series that has been shifted in data. A sequence generation step for generating a sub data sequence by dividing an arbitrary data sequence having an autocorrelation characteristic higher than an autocorrelation value between the number of elements of the input signal;
When the input signal element and the sub data sequence are associated one-to-one, and the input signal satisfies a predetermined criterion, the input signal is associated with the sub data sequence to each element of the sub data sequence. The sub-data sequence subjected to the operation is combined at the position when divided in the sequence generation step to generate modulation data, and the input signal satisfies the predetermined criterion. If not, the sign of each element of the sub-data series is inverted, the element of the input signal associated with the sub-data series is inverted and multiplied, and the sub-data series subjected to the calculation is calculated A modulation step for generating the modulation data by arranging and synthesizing at the position when divided in the sequence generation step;
An IFFT step for performing an inverse fast Fourier transform on the modulated data;
A combining step of combining the operation results of the IFFT step to generate a data symbol;
Generating and transmitting a transmission frame including the data symbols;
A communication method comprising: A communication method performed by a communication device that communicates with other devices by wireless communication of an orthogonal frequency division multiplex communication method,
A receiving step for receiving a transmission frame including data symbols;
An FFT step of extracting the data symbols and performing serial-parallel conversion and performing fast Fourier transform to generate a received parallel signal;
A data series that is a set of data of the same number as the number of elements of the received parallel signal, and an autocorrelation value between the same data series that is not shifted in data is a data series that is shifted in data Using a predetermined reception-side data sequence having an autocorrelation characteristic that is higher than an autocorrelation value between the reception-side data sequence and the received parallel signal or an inverse fast Fourier of the reception-side data sequence A synchronization step of detecting a synchronization position of the data symbol based on a correlation between the data symbol obtained by performing the transformation and the data symbol;
Based on the synchronization position detected in the synchronization step, the absolute value of the received parallel signal generated from the data symbol extracted in the FFT step or data obtained by parallel-serial conversion of the received parallel signal is greater than or equal to a predetermined threshold value A determination step of replacing the value of an element with 1 and replacing the value of an element other than the element with 0 to generate post-determination data;
The post-determination data is divided into a predetermined number to generate post-determination sub-data, and each element is associated with the post-determination sub-data on a one-to-one basis, and is associated with the post-determination sub-data that satisfies a predetermined criterion. When demodulated data is generated in which the value of the element is 1 and the value of the elements other than the element is 0, and the correlation is a negative correlation, each element of the demodulated data is A demodulation step that replaces with an inverted value;
A communication method comprising:

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