JP5888219B2 - COMMUNICATION DEVICE AND COMMUNICATION METHOD - Google Patents

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 the orthogonal frequency division multiplexing communication apparatus of Patent Literature 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 the orthogonal frequency division multiplexing communication apparatus of Patent Document 1, it is necessary to perform iterative calculation processing to calculate the optimum phase for reducing the PAPR, and to control the phase for each subcarrier.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce PAPR and simplify processing for reducing 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,
Modulation means for modulating the input signal with a predetermined modulation method to generate a modulation signal;
Insertion means for inserting a predetermined complex number different from a value that can be taken by each element of the modulation signal immediately before or after each element of the modulation signal, and generating post-insertion data in which the number of elements matches the size of the fast Fourier transform ,
First IFFT means for performing inverse fast Fourier transform of the post-insertion data;
Shift means for generating inverted data by shifting the inverted data generated by reversing the order of the elements of the inserted data in a predetermined direction a predetermined number of times that is a multiple of 2;
A second IFFT means for performing an inverse fast Fourier transform on the data obtained by adding the shift data to the post-insertion data;
A peak-to-average power ratio of the baseband signal is calculated based on each of the calculation result of the first IFFT means and the calculation result of the second IFFT means, and whether the peak-to-average power ratio meets a predetermined standard Determining means for determining whether or not;
The predetermined number of shifts of the inverted data is changed until the calculation result of the first IFFT means or the calculation result of the second IFFT means whose peak-to-average power ratio meets a predetermined standard is detected. Repetitive means for performing the processing of the shift means to generate the shift data, and repeatedly performing the processing of the second IFFT means and the determination means for the shift data;
Transmission means for generating a baseband signal based on the calculation result of the first IFFT means or the calculation result of the second IFFT means that matches the predetermined standard, and generating and transmitting a transmission signal from the baseband signal When,
It is characterized by providing.

  Preferably, the insertion means sets the predetermined complex number to 0, and inserts 0 immediately before or after each element of the modulation signal.

  Preferably, the inserting means inserts the predetermined complex number immediately after each element of the modulation signal.

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 signal and generating a baseband signal;
FFT means for performing serial-parallel conversion on the baseband signal and performing fast Fourier transform to generate converted data;
Based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data, one of the first data and the second data is determined. Disassembling means for generating inverted reception data by reversing the order of the other element as reference data;
Determining whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction, repeatedly performing the predetermined number of times, and shifting the correlation with the reference data When the inverted reception data exists, data having each element as a value obtained by subtracting a predetermined complex number from each element of the reference data and an average value of each element of the inverted reception data is used as the restoration data, and the reference data If there is no shifted inverted reception data having a correlation with the correlation analysis means using the reference data as restored data,
Demodulation means for demodulating the restored data by a predetermined modulation method;
It is characterized by providing.

  Preferably, the correlation analysis unit sets the predetermined complex number to 0, and when there is the inverted inverted reception data having a correlation with the reference data, each element of the reference data and each of the inverted reception data Data having an element average value as each element is referred to as the restoration data.

  Preferably, the decomposing means generates the inverted reception data by using the first data as the reference data and reversing the order of the elements of the second data.

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,
A modulation step of modulating the input signal with a predetermined modulation method to generate a modulated signal;
An insertion step of inserting a predetermined complex number different from a value that can be taken by each element of the modulation signal immediately before or after each element of the modulation signal, and generating post-insertion data in which the number of elements matches the size of the fast Fourier transform; ,
A first IFFT step for performing an inverse fast Fourier transform on the post-insertion data;
A shift step of generating the shift data by shifting the inverted data generated by reversing the order of the elements of the post-insertion data in a predetermined direction a predetermined number of times that is a multiple of 2;
A second IFFT step for performing an inverse fast Fourier transform of data obtained by adding the shift data to the post-insertion data;
A peak-to-average power ratio of the baseband signal is calculated based on each of the calculation result of the first IFFT step and the calculation result of the second IFFT step, and whether the peak-to-average power ratio meets a predetermined criterion A determination step for determining whether or not;
The predetermined number of shifts of the inverted data is changed until the calculation result of the first IFFT step or the calculation result of the second IFFT step in which the peak-to-average power ratio meets a predetermined criterion is detected. Performing the shift step to generate the shift data, and repeatedly performing the second IFFT step and the determination step for the shift data;
A transmission step of generating a baseband signal based on the calculation result of the first IFFT step or the calculation result of the second IFFT step that matches the predetermined criterion, and generating and transmitting a transmission signal from the baseband signal When,
It is characterized by providing.

  Preferably, in the inserting step, the predetermined complex number is set to 0, and 0 is inserted immediately before or after each element of the modulated signal.

  Preferably, in the inserting step, the predetermined complex number is inserted immediately after each element of the modulated signal.

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 reception step of receiving a transmission signal and generating a baseband signal;
An FFT step of performing serial-parallel conversion of the baseband signal and performing fast Fourier transform to generate converted data;
Based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data, one of the first data and the second data is determined. A decomposition step for generating inverted reception data by reversing the order of the other element as reference data;
Determining whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction, repeatedly performing the predetermined number of times, and shifting the correlation with the reference data When the inverted reception data exists, data having each element as a value obtained by subtracting a predetermined complex number from each element of the reference data and an average value of each element of the inverted reception data is used as the restoration data, and the reference data A correlation analysis step using the reference data as restored data when there is no shifted inverted reception data having a correlation with
A demodulation step of demodulating the restored data with a predetermined modulation method;
It is characterized by providing.

  Preferably, in the correlation analyzing step, when the predetermined complex number is set to 0 and there is the inverted inverted reception data that has a correlation with the reference data, each element of the reference data and each of the inverted reception data Data having an element average value as each element is referred to as the restoration data.

  Preferably, in the disassembling step, the first received data is used as the reference data, and the inverted received data is generated by reversing the order of the elements of the second data.

  According to the present invention, it is possible to reduce the PAPR and simplify the process for reducing the PAPR in the 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 example of the arithmetic processing by the transmission side 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 example of the arithmetic processing by the receiving side which the communication apparatus which concerns on embodiment performs. It is a figure which shows the example of the arithmetic processing by the receiving side 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 baseband signal in the communication apparatus which concerns on embodiment. It is a figure which shows the BER characteristic in the communication apparatus which concerns on embodiment. It is the schematic of the delay profile of the transmission line used for simulation. It is a figure which shows the relationship between BER and the moving speed in the communication apparatus which concerns on embodiment.

  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 DFT size.

  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 serial-parallel conversion unit 12, an insertion unit 13, an IFFT unit 14, an inversion unit 15, a shift unit 16, a determination unit 17, a transmission unit 18, 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 parallel-serial conversion unit 32, a correlation unit 33, a decomposition unit 34, an FFT unit 35, a reception unit 36, and transmission / reception switching. The unit 37 is provided. 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 modulation unit 11 modulates the input signal using a predetermined modulation method, generates a modulation signal, and sends the modulated signal to the serial-parallel conversion unit 12. The predetermined modulation method is, for example, QPSK (Quadrature Phase-Shift Keying). The serial / parallel conversion unit 12 performs serial / parallel conversion on the modulated signal and sends it to the insertion unit 13. The insertion unit 13 inserts a predetermined complex number different from any value that can be taken by each element of the modulation signal immediately before or after each element of the modulation signal subjected to serial-parallel conversion, and the number of elements matches the FFT size. Generate post data. When the modulation method is QPSK and the absolute value of each element of the modulation signal is A, the possible values of each element of the modulation signal are A · e ^{i (π / 4)} and A · e ^{i (3π / 4). )} , A · e ^{i (−π / 4)} , and A · e ^{i (−3π / 4)} . Therefore, when the modulation method is QPSK, the predetermined complex number is a complex number different from any of the above values. The insertion unit 13 sends the post-insertion data to the IFFT unit 14 and the inverting unit 15.

  Here, as an example, the insertion unit 13 sets a predetermined complex number to 0, for example, and inserts 0 immediately after each element of the modulation signal subjected to serial-parallel conversion. The modulation signal d subjected to serial / parallel conversion is expressed by the following equation (1), and the data f after insertion is expressed by the following equation (2). If the FFT size is N, M = N / 2 in the equation. The subscript T in the formula indicates that the matrix is transposed. The same applies to the following description.

  The inversion unit 15 generates inverted data by reversing the order of the elements of the post-insertion data, and sends the inverted data to the shift unit 16. The inverted data g generated based on the post-insertion data f represented by the above equation (2) is represented by the following equation (3).

The shift unit 16 shifts the inverted data in a predetermined direction a predetermined number of times that is a multiple of 2, generates shift data, and sends the shift data to the IFFT unit 14. Shift data g ^(k) generated by shifting the inverted data g represented by the above expression (3) k times upward, for example, is represented by the following expression (4). K in the parentheses of the subscript represents the number of shifts, and k = 2i holds. Note that i is an integer of 0 or more and less than M. The direction in which the inverted data g is shifted is not limited to the upward direction, but is arbitrary.

The post-computation data h, which is data ^obtained by adding the shift data g ^(k) to the post-insertion data f, is expressed by the following equation (5). The IFFT unit 14 performs IFFT on the post-insertion data f and the post-computation data h, and sends the computation result to the determination unit 17.

FIG. 3 is a diagram illustrating an example of arithmetic processing on the transmission side performed by the communication device according to the embodiment. The number of elements of the modulation signal was 8 and the FFT size was 16. The horizontal axis is the element, and the vertical axis is the value of the element. For ease of explanation, only the real part of each element is shown. The insertion unit 13 inserts 0 immediately after each element of the modulation signal d shown in FIG. 3A to generate post-insertion data f shown in FIG. The inverting unit 15 reverses the order of the elements of the post-insertion data f to generate the inverted data g shown in FIG. For example, assuming that k = 6, the shift unit 16 shifts the inverted data six times upward to generate shift data g ^(k) shown in FIG. FIG. 3E shows post-computation data h generated by adding shift data g ^(k) to post-insertion data f. The IFFT unit 14 performs an IFFT of the post-insertion data f shown in FIG. 3B, and performs an IFFT of the post-computation data h shown in FIG.

The determination unit 17 calculates the PAPR of the baseband signal based on the calculation result of the post-insertion data f in the IFFT unit 14 and the baseband signal based on the calculation result of the post-computation data h in the IFFT unit 14, respectively. It is determined whether or not it matches. If the PAPR based on the calculation result in the IFFT unit 14 does not meet a predetermined standard for both the inserted data f and the calculated data h, the determination unit 17 notifies the shift unit 16 to that effect. The shift unit 16 generates new shift data g ^{(k ′)} by changing the number of shifts of the inverted data g. The shift unit 16 generates new shift data g ^{(k ′)} , and the IFPR unit 14 and the determination unit 17 perform the above-described processing based on the new shift data g ^{(k ′).} Repeat until the operation result that matches is detected.

It is possible to reduce the PAPR of the baseband signal by repeating the above processing until the PAPR detects a calculation result that matches a predetermined criterion. In the above iterative process, the IFFT unit 14 and the determination unit 17 process only the post-computation data h based on the new shift data g ^{(k ′)} , and do not repeat the process for the post-insertion data f. It can be constituted as follows.

  The controller 20 controls the shift unit 16, the IFFT unit 14, and the determination unit 17 to repeat the above-described processing, and performs an operation as a repeating unit.

  When the PAPR detects a calculation result that matches a predetermined criterion, the determination unit 17 sends the calculation result in the IFFT unit 14 that matches the predetermined criterion to the transmission unit 18. The determination unit 17 repeats the above-described processing until the shift of the data of the inverted data g in the shift unit 16 is completed, and detects the calculation result in the IFFT unit 14 having the lowest PAPR, or the PAPR is lower than a predetermined value. The calculation result in the small IFFT unit 14 can be detected.

  The transmission unit 18 generates a baseband signal based on the calculation result in the IFFT unit 14 that matches the received predetermined standard, generates a transmission signal from the baseband signal, and transmits the transmission signal via the transmission / reception switching unit 37 and the antenna 10. Send transmission signals to other devices.

  FIG. 4 is a flowchart illustrating an example of a transmission control operation performed by the communication device according to the embodiment. The modulation unit 11 modulates the input signal with a predetermined modulation method to generate a modulation signal, and the serial / parallel conversion unit 12 performs serial / parallel conversion on the modulation signal (step S110). The insertion unit 13 inserts a predetermined complex number immediately before or immediately after each element of the modulation signal subjected to serial-parallel conversion, and generates post-insertion data f in which the number of elements matches the FFT size (step S120). The IFFT unit 14 performs IFFT of the inserted data f (step S130). The inverting unit 15 generates the inverted data g by reversing the order of the elements of the post-insertion data f (step S140).

The shift unit 16 shifts the inverted data g in a predetermined direction by a predetermined number of times that is a multiple of 2 to generate shift data g ^(k) (step S150). For example, assuming that the number of shifts is 0, shift data g ^(k) = g. The IFFT unit 14 performs IFFT of post-computation data h that is data ^obtained by adding the shift data g ^(k) to the post-insertion data f (step S160). The determination unit 17 calculates the PAPR of the baseband signal based on the calculation result of the post-insertion data f in the IFFT unit 14 and the baseband signal based on the calculation result of the post-computation data h in the IFFT unit 14, respectively. It is determined whether or not (step S170).

If the PAPR does not detect a calculation result that matches a predetermined standard (step S180; N), 1 is added to the number of shifts (step S190), and the process returns to step S150, and a new one based on the new number of shifts. Shift data g ^{(k ′)} is generated, and the above-described processing is repeated. When the PAPR detects a calculation result that matches a predetermined criterion (step S180; Y), the transmission unit 18 generates a baseband signal based on the calculation result that matches the predetermined criterion, and starts from the baseband signal. A transmission signal is generated, and the transmission signal is transmitted to another device via the transmission / reception switching unit 37 and the antenna 10 (step S200). When the transmission process in step S200 is completed, the process ends. Note that the above-described repetition method is an example, and the method of changing the number of shifts is arbitrary.

  Processing on the receiving side will be described below. The receiving unit 36 receives a transmission signal via the antenna 10 and the transmission / reception switching unit 37, generates a baseband signal, performs serial-parallel conversion, and sends the signal to the FFT unit 35. The FFT unit 35 performs FFT of the baseband signal that has been serial-parallel converted to generate converted data, and sends the converted data to the decomposition unit 34.

  The decomposition unit 34 determines one of the first data and the second data based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data. Is used as reference data, and the order of the other element is reversed to generate inverted received data. The decomposition unit 34 sends the reference data and the inverted reception data to the correlation unit 33. For example, when a predetermined complex number is inserted immediately after each element of the modulation signal subjected to serial-parallel conversion in the insertion unit 13 on the transmission side, the decomposing unit 34 uses the first data as the reference data and the second data The reverse reception data is generated by reversing the order. Further, for example, when a predetermined complex number is inserted immediately before each element of the modulation signal subjected to serial-parallel conversion in the insertion unit 13 on the transmission side, the decomposing unit 34 uses the second data as the reference data and the first data The reverse received data is generated by reversing the order. It is assumed that information on the insertion position of a predetermined complex number on the transmission side is held in advance on the reception side.

  The correlation unit 33 repeatedly determines whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction while changing the predetermined number of times. The correlation unit 33 determines that there is a correlation between the reference data and the shifted inverted reception data if the correlation value between the reference data and the shifted inverted reception data is equal to or greater than the threshold value. The threshold is determined according to the maximum value that the correlation value can take. For example, when performing normalized correlation analysis, the threshold is set to 3/4.

  When there is shifted inverted reception data having a correlation with the reference data, the correlator 33 determines a predetermined value from the average value of each element of the reference data and each element of the shifted inverted reception data having a correlation with the reference data. Data whose elements are the values obtained by subtracting the complex number of are taken as restored data. The predetermined complex number is the same as the predetermined complex number used in the insertion unit 13 on the transmitting side, and information on the predetermined complex number is held in advance on the receiving side. By taking the average value of each element of the reference data and each element of the inverted inverted reception data that has a correlation with the reference data, the noise component contained in the data can be reduced.

  As represented by the above expression (2), the insertion unit 13 sets, for example, a predetermined complex number to 0, and inserts 0 immediately after each element of the modulation signal subjected to serial-parallel conversion. When there is shifted inverted reception data having a correlation with the reference data, the correlator 33 calculates each element of the reference data and the average value of each element of the shifted inverted reception data having a correlation with the reference data. The element data is taken as the restoration data.

  When there is no shifted inverted reception data having a correlation with the reference data, the correlator 33 uses the reference data as restored data. The correlation unit 33 sends the restored data to the parallel / serial conversion unit 32.

  FIG. 5 is a diagram illustrating an example of arithmetic processing on the reception side performed by the communication device according to the embodiment. The horizontal axis is the element, and the vertical axis is the value of the element. For ease of explanation, only the real part of each element is shown. Assume that the calculation process shown in FIG. 3 is performed on the transmission side, and a baseband signal based on post-computation data h shown in FIG. FIG. 5A shows the converted data. FIG. 5B shows the first data, and FIG. 5C shows the second data. The decomposing unit 34 uses the first data as reference data, and generates inverted reception data by reversing the order of the second data as shown in FIG.

  The correlator 33 repeats changing the predetermined number of shifts to determine whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction. Data obtained by shifting the inverted reception data, which is a parallel signal shown in FIG. 5D, upward three times matches the reference data, and therefore the correlation value is equal to or greater than the threshold value. The correlator 33 uses, as restoration data, data having each element as an average value of each element of the reference data and each element of the inverted reception data shifted upward three times.

  FIG. 6 is a diagram illustrating an example of arithmetic processing on the reception side performed by the communication device according to the embodiment. The way of viewing the figure is the same as in FIG. Assume that the calculation process shown in FIG. 3 is performed on the transmission side, and a baseband signal based on the post-insertion data f shown in FIG. 3B is transmitted. FIG. 6A shows the converted data. FIG. 6B shows the first data, and FIG. 6C shows the second data and the inverted reception data.

  The correlator 33 repeats changing the predetermined number of shifts to determine whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction. None of the inverted inverted received data has a correlation with the reference data. Since there is no shifted inverted reception data having a correlation with the reference data, the correlator 33 uses the reference data as restored data.

  In either case of FIG. 5 and FIG. 6, the restored data matches the modulated signal shown in FIG. The parallel-serial conversion unit 32 performs parallel-serial conversion on the restored data and sends it to the demodulation unit 31. The demodulator 31 demodulates the restored data that has undergone parallel-serial conversion using a predetermined modulation method, and restores the input signal.

  FIG. 7 is a flowchart illustrating an example of reception control operation performed by the communication device according to the embodiment. The receiving unit 36 receives a transmission signal via the antenna 10 and the transmission / reception switching unit 37, generates a baseband signal, and performs serial-parallel conversion (step S310). The FFT unit 35 performs FFT of the baseband signal that has been subjected to serial-parallel conversion to generate post-conversion data (step S320). The decomposition unit 34 determines one of the first data and the second data based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data. Is used as reference data, and the order of the other element is reversed to generate inverted reception data (step S330).

  The correlation unit 33 initializes the number of shifts with 0 (step S340). The correlation unit 33 determines whether or not there is a correlation between the reference data and the inverted reception data shifted 0 times upward (step S350). If there is a correlation between the reference data and the shifted inverted reception data (step S360; Y), the correlation unit 33 calculates the average value of each element of the reference data and each element of the shifted inverted reception data. Data having each element as a value obtained by subtracting a predetermined complex number is set as restoration data (step S370).

  If there is no correlation between the reference data and the inverted inverted reception data (step S360; N), the process proceeds to step S380. In the above example, the number of shifts is 0 and not N−1 (step S380; N). Therefore, 1 is added to the number of shifts (step S390), the process returns to step S350, and the above process is repeated. When the above process is repeated and the number of shifts reaches N−1 (step S380; Y), the correlator 33 sets the reference data as restored data (step S400). The parallel-serial converter 32 performs parallel-serial conversion on the restored data, and the demodulator 31 demodulates the restored data subjected to parallel-serial conversion using a predetermined modulation method to restore the input signal (step S410). When the restoration process in step S410 is completed, the process ends. Note that the above-described repetition method is an example, and the method of changing the number of shifts is arbitrary.

  As described above, according to the communication device 1 according to the embodiment of the present invention, in the OFDM communication method, a predetermined calculation process is performed on the modulated signal, and a calculation result in the IFFT unit 14 that satisfies a predetermined criterion is detected. It is possible to reduce the PAPR by repeating the process up to. Further, repeating the processing of the shift unit 16, IFFT unit 14, and determination unit 17 as described above is a simpler method than the calculation processing by the sequential determination method, and the embodiment of the present invention According to the communication device 1, it is possible to simplify the process of reducing the PAPR.

  In addition, when the restoration data is generated based on the average value of each element of the reference data and each element of the inverted inverted reception data having a correlation with the reference data on the receiving side, the noise component included in the data can be reduced. It becomes possible.

(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 the baseband signal and repeatedly calculating the PAPR for the related art and the invention according to the present embodiment. The modulation method is QPSK, the FFT size is 2048, and the PAPR CCDF (Complementary Cumulative Distribution Function) of the invention according to the present embodiment, that is, the characteristics of PAPR occurrence probability are compared. The prior art is a method of generating a baseband signal by performing serial-parallel conversion on a signal obtained by modulating an input signal by a predetermined modulation method without performing the above-described arithmetic processing and performing IFFT.

  Here, as an example, the insertion unit 13 performs a simulation using post-insertion data f generated by inserting 0 immediately after each element of the modulation signal subjected to serial-parallel conversion having 1024 elements. FIG. 8 is a diagram illustrating the CCDF characteristics of the PAPR of the baseband signal in the communication device according to the embodiment. The horizontal axis is PAPR (unit: dB), and the vertical axis is PAPR CCDF. The CCDF characteristic of the PAPR of the prior art is a thin solid line graph, and the CCDF characteristic of the PAPR of the invention according to the present embodiment is a solid line graph. The PAPR of the invention according to the present embodiment is reduced as compared with the prior art.

  The simulation was performed using the same signal in which the phase of each element of the signal modulated by a predetermined modulation method is matched, for example, the element values are all 0, as an input signal. The PAPR of the prior art is 33.11 dB, while the PAPR of the invention according to the present embodiment is 30.10 dB. Even when the input signals are the same signal, the PAPR of the invention according to the present embodiment is reduced as compared with the prior art.

  A simulation was similarly performed for BER (Bit Error Rate). FIG. 9 is a diagram illustrating BER characteristics in the communication device according to the embodiment. The horizontal axis represents Eb / No (Energy per Bit to NOise power spectral density ratio), and the vertical axis represents BER. The unit of Eb / No is dB. The BER of the prior art is a graph in which plot points are represented by squares, and the BER of the invention according to the present embodiment is a graph in which plot points are represented by triangles. As shown in FIG. 9, the BER of the invention according to the present embodiment is improved compared to the prior art, particularly in the range where the noise level is high.

  Next, the effect of fading in the transmission path was simulated. The number of multipaths was 6, and the number of elementary waves arriving at the receiving antenna was 32. Further, the values shown in Table 1 are shown as a delay profile indicating the relationship between the delay time of the delayed wave composed of elementary waves and the average power that is the average of received power in a predetermined section including a predetermined number of wavelengths at the antenna. Using. FIG. 10 is a schematic diagram of the delay profile of the transmission path used in the simulation.

  Regarding Doppler shift, the frequency of the reference subcarrier was set to 5.6 GHz, and the moving speed of the communication device on the transmission side was made variable. The OFDM communication system used in the simulation did not use interleaving and did not perform error correction. Further, a signal having all element values of 1 was used as a pilot signal, zero-order interpolation was performed on the receiving side, and equalization was performed using zero forcing.

  A change in the simulated BER will be described. FIG. 11 is a diagram illustrating a relationship between the BER and the moving speed in the communication device according to the embodiment. The horizontal axis is Eb / No, and the vertical axis is BER. The unit of Eb / No is dB. The BER of the prior art is a graph in which plot points are represented by squares, and the BER of the invention according to the present embodiment is a graph in which plot points are represented by triangles. The BER was simulated by changing the moving speed. FIG. 11A shows the BER when the moving speed is 0 km / h, FIG. 11B shows the BER when the moving speed is 50 km / h, and FIG. 11C shows the BER when the moving speed is 100 km / h. is there. It can be seen that as the moving speed increases, the BER deteriorates, and the slower the moving speed, the greater the degree of improvement of the BER according to the invention according to the present embodiment.

  According to the above-described simulation, in the present embodiment, predetermined arithmetic processing is performed on the modulation signal, and the processing is repeated until a baseband signal satisfying a predetermined criterion is detected, thereby reducing PAPR and improving BER. I found out that I could do it.

  The embodiment of the present invention is not limited to the above-described embodiment. The modulation method of the modulation unit 11 is not limited to QPSK, and PSK (Phase Shift Keying) other than QPSK, Quadrature Amplitude Modulation (QAM), or the like can be used. In the above-described embodiment, a predetermined complex number is inserted immediately before or immediately after each element of the modulation signal subjected to serial / parallel conversion by the serial / parallel conversion unit 12, but the order of the serial / parallel conversion unit 12 and the insertion unit 13 is changed. You may change it. In other words, the inserted complex data is inserted immediately before or immediately after each element of the modulated signal generated by modulating the input signal with a predetermined modulation method to generate post-insertion data. You may comprise so that serial-parallel conversion may be carried out.

In the above-described embodiment, the insertion unit 13 uses 0 as the predetermined complex number, but the predetermined complex number is not limited to 0. When the insertion unit 13 uses a predetermined complex number α, data obtained by replacing 0 in the expressions (2), (3), and (4) with α is the post-insertion data f, the inverted data g, and the shift data g ^{( k)} . The post-computation data h is expressed by the following equation (6).

  When the baseband signal based on the post-computation data h represented by the above equation (6) is transmitted, the receiving-side correlation unit 33 calculates the average value of each element of the reference data and each element of the inverted reception data. Data having each element as a value obtained by subtracting a predetermined complex number is taken as restored data. Further, the correlator 33 obtains data in which each element is an average value of each element of data obtained by subtracting a predetermined complex number from each element of the reference data and data obtained by subtracting the predetermined complex number from each element of the inverted reception data. It may be restored data.

  The IFFT unit 14 may be configured to perform IDFT instead of IFFT, and the FFT unit 35 may be configured to perform DFT instead of FFT.

1 communication equipment
10 Antenna
11 Modulator
12 Series-parallel converter
13 Insertion part
14 IFFT section
15 Reverse part
16 Shift section
17 Judgment part
18 Transmitter
20 controller
21 CPU
22 I / O
23 RAM
24 ROM
31 Demodulator
32 Parallel to serial converter
33 Correlator
34 Disassembly part
35 FFT section
36 Receiver
37 Transmission / reception switching unit

Claims (12)

A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
Modulation means for modulating the input signal with a predetermined modulation method to generate a modulation signal;
Insertion means for inserting a predetermined complex number different from a value that can be taken by each element of the modulation signal immediately before or after each element of the modulation signal, and generating post-insertion data in which the number of elements matches the size of the fast Fourier transform ,
First IFFT means for performing inverse fast Fourier transform of the post-insertion data;
Shift means for generating inverted data by shifting the inverted data generated by reversing the order of the elements of the inserted data in a predetermined direction a predetermined number of times that is a multiple of 2;
A second IFFT means for performing an inverse fast Fourier transform on the data obtained by adding the shift data to the post-insertion data;
A peak-to-average power ratio of the baseband signal is calculated based on each of the calculation result of the first IFFT means and the calculation result of the second IFFT means, and whether the peak-to-average power ratio meets a predetermined standard Determining means for determining whether or not;
The predetermined number of shifts of the inverted data is changed until the calculation result of the first IFFT means or the calculation result of the second IFFT means whose peak-to-average power ratio meets a predetermined standard is detected. Repetitive means for performing the processing of the shift means to generate the shift data, and repeatedly performing the processing of the second IFFT means and the determination means for the shift data;
Transmission means for generating a baseband signal based on the calculation result of the first IFFT means or the calculation result of the second IFFT means that matches the predetermined standard, and generating and transmitting a transmission signal from the baseband signal When,
A communication device comprising:   2. The communication apparatus according to claim 1, wherein the inserting unit sets the predetermined complex number to 0 and inserts 0 immediately before or immediately after each element of the modulation signal.   The communication device according to claim 1, wherein the insertion unit inserts the predetermined complex number immediately after each element of the modulation signal. A communication device that communicates with other devices by orthogonal frequency division multiplex communication wireless communication,
Receiving means for receiving a transmission signal and generating a baseband signal;
FFT means for performing serial-parallel conversion on the baseband signal and performing fast Fourier transform to generate converted data;
Based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data, one of the first data and the second data is determined. Disassembling means for generating inverted reception data by reversing the order of the other element as reference data;
Determining whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction, repeatedly performing the predetermined number of times, and shifting the correlation with the reference data When the inverted reception data exists, data having each element as a value obtained by subtracting a predetermined complex number from each element of the reference data and an average value of each element of the inverted reception data is used as the restoration data, and the reference data If there is no shifted inverted reception data having a correlation with the correlation analysis means using the reference data as restored data,
Demodulation means for demodulating the restored data by a predetermined modulation method;
A communication device comprising:   The correlation analysis means sets the predetermined complex number to 0, and when there is the shifted inverted reception data having a correlation with the reference data, the average of each element of the reference data and each element of the inverted reception data 5. The communication apparatus according to claim 4, wherein data having values as elements is the restored data.   6. The communication according to claim 4, wherein the decomposing means generates the inverted reception data by using the first data as the reference data and reversing the order of elements of the second data. Machine. 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 modulation step of modulating the input signal with a predetermined modulation method to generate a modulated signal;
An insertion step of inserting a predetermined complex number different from a value that can be taken by each element of the modulation signal immediately before or after each element of the modulation signal, and generating post-insertion data in which the number of elements matches the size of the fast Fourier transform; ,
A first IFFT step for performing an inverse fast Fourier transform on the post-insertion data;
A shift step of generating the shift data by shifting the inverted data generated by reversing the order of the elements of the post-insertion data in a predetermined direction a predetermined number of times that is a multiple of 2;
A second IFFT step for performing an inverse fast Fourier transform of data obtained by adding the shift data to the post-insertion data;
A peak-to-average power ratio of the baseband signal is calculated based on each of the calculation result of the first IFFT step and the calculation result of the second IFFT step, and whether the peak-to-average power ratio meets a predetermined criterion A determination step for determining whether or not;
The predetermined number of shifts of the inverted data is changed until the calculation result of the first IFFT step or the calculation result of the second IFFT step in which the peak-to-average power ratio meets a predetermined criterion is detected. Performing the shift step to generate the shift data, and repeatedly performing the second IFFT step and the determination step for the shift data;
A transmission step of generating a baseband signal based on the calculation result of the first IFFT step or the calculation result of the second IFFT step that matches the predetermined criterion, and generating and transmitting a transmission signal from the baseband signal When,
A communication method comprising:   8. The communication method according to claim 7, wherein, in the inserting step, the predetermined complex number is set to 0, and 0 is inserted immediately before or immediately after each element of the modulation signal.   9. The communication method according to claim 7, wherein, in the inserting step, the predetermined complex number is inserted immediately after each element of the modulated signal. 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 reception step of receiving a transmission signal and generating a baseband signal;
An FFT step of performing serial-parallel conversion of the baseband signal and performing fast Fourier transform to generate converted data;
Based on the first data composed of odd-numbered elements of the converted data and the second data composed of even-numbered elements of the converted data, one of the first data and the second data is determined. A decomposition step for generating inverted reception data by reversing the order of the other element as reference data;
Determining whether or not there is a correlation between the reference data and the inverted reception data shifted a predetermined number of times in a predetermined direction, repeatedly performing the predetermined number of times, and shifting the correlation with the reference data When the inverted reception data exists, data having each element as a value obtained by subtracting a predetermined complex number from each element of the reference data and an average value of each element of the inverted reception data is used as the restoration data, and the reference data A correlation analysis step using the reference data as restored data when there is no shifted inverted reception data having a correlation with
A demodulation step of demodulating the restored data with a predetermined modulation method;
A communication method comprising:   In the correlation analysis step, when the predetermined complex number is set to 0 and there is the inverted inverted reception data that is correlated with the reference data, the average of each element of the reference data and each element of the inverted reception data 11. The communication method according to claim 10, wherein data having values as elements is used as the restored data.   12. The communication according to claim 10 or 11, wherein, in the disassembling step, the inverted reception data is generated by using the first data as the reference data and reversing the order of elements of the second data. Method.

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