Signal processing method, program, and wireless transmission device

Abstract

To provide a signal processing method, a program, and a wireless transmitting device suitable from the viewpoint of suppressing ACLR and OOBE.SOLUTION: A signal processing method includes the steps of: applying a cyclic prefix to a generated OFDM signal; designing a pulse shaping filter; and applying pulse shaping to the OFDM signal to which the cyclic prefix is applied using the designed pulse shaping filter. In the step of designing a pulse shaping filter, the pulse shaping filter is designed to reduce unnecessary radiated power using a modulation symbol of each subcarrier, a center frequency of each subcarrier, FFT size, CP length, and pulse shaping filter length.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a signal processing method, a program, and a wireless transmission device.

Background Art

[0002] In recent wireless communications, the OFDM (Orthogonal Frequency Division Multiplexing) method is adopted as a modulation method. In the OFDM method, in order to avoid inter-symbol interference in which the delayed wave of the previous OFDM symbol temporally affects the next OFDM symbol, a guard interval called a cyclic prefix (CP) is provided at the head of the OFDM symbol.

[0003] In the OFDM method and the OFDM (CP-OFDM) method using CP, since the signal becomes discontinuous between adjacent symbols, there is a problem that the adjacent channel leakage power ratio (ACLR) and out-of-band emission (OOBE) increase, interfering with other adjacent wireless systems. Non-Patent Document 1 discloses a W-OFDM (Windowed-OFDM) method in which a pulse shaping filter is multiplied on the time axis to perform pulse shaping as a typical method for reducing ACLR and OOBE.

[0004] When trying to strongly suppress ACLR and OOBE in the W-OFDM method, it is necessary to increase the length of the pulse shaping filter. When the length of the pulse shaping filter is increased, the overlapping interval with the OFDM symbols on both sides becomes longer, resulting in inter-symbol interference. As a technique that achieves both suppression of ACLR and OOBE and reduction of inter-symbol interference, Patent Document 1 discloses a technique for selecting the length and shape of the pulse shaping filter according to wireless requirements specifications.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 6164630 [Non-Patent Document]

[0006] [Non-Patent Document 1] Institute of Electronics, Information and Communication Engineers, "Knowledge Base", Group 4 - Chapter 6 - Section 2, ver.1 / 2019 / 5 / 15, [online], [searched on January 31, 2022], Internet <URL:https: / / www.ieice-hbkb.org / files / 04 / 04gun_06hen_02.pdf> [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] By the way, as a pulse shaping filter used in the W-OFDM system, various window functions such as a raised cosine window, a root raised cosine window, a trapezoidal window, and a Hamming window may be used in addition to the raised cosine window. However, these window functions are originally used for spectrum analysis and are designed to satisfy the required performance of frequency resolution and dynamic range. For this reason, there is a problem that they are not necessarily in an optimal shape from the viewpoint of suppressing ACLR and OOBE. Therefore, for example, when trying to achieve ACLR and OOBE required for a wireless transmission device, the length of the pulse shaping filter may become long and the inter-symbol interference may become large. Or, if the length of the pulse shaping filter is shortened to reduce the inter-symbol interference, the required performance of ACLR and OOBE may not be satisfied.

[0008] The present invention has been made in view of the above, and an object thereof is to provide a signal processing method, a program, and a wireless transmission device suitable from the viewpoint of suppressing ACLR and OOBE. [Means for Solving the Problems]

[0009] In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention comprises the steps of: adding a cyclic prefix to a generated OFDM signal; designing a pulse shaping filter; and using the designed pulse shaping filter to perform pulse shaping on the OFDM signal to which the cyclic prefix has been added, wherein the step of designing the pulse shaping filter comprises: The number of OFDM symbols L, the OFDM symbol length Nsym, the sample rate Fs, the s Modulation symbols for subcarriers a k、l (where a k、l is the k-th input modulation symbol of the l-th OFDM symbol) and, s carrier center frequency f k (where f k is the center frequency of the subcarrier corresponding to the k-th input modulation symbol) and, the number of subcarriers Nsc, and FFT Size N FFT And, CP chief N CP and the pulse shaping filter length N PS Using Based on the vector S representing the spectrum of the OFDM signal before pulse shaping calculated according to Equations (5a), (5b), Equation (2), and Equation (3), the vector w representing the filter shape of the pulse shaping filter calculated according to Equation (1), and the matrix B for converting the vector w into the spectrum calculated according to Equations (4a) and (4b), the range of m is calculated such that νm is in the range of the unnecessary radiation band This is a signal processing method for designing the pulse shaping filter so as to reduce unwanted radiation power.

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[0011] In the step of designing the pulse shaping filter, the pulse shaping filter may be designed so as to minimize the unwanted radiation power.

[0012] The pulse shaping filter may be a filter with real components, a filter with a shape that is point-symmetric in time, or a filter with real components and a shape that is point-symmetric in time.

[0013] In the step of designing the pulse shaping filter, the pulse shaping filter may be designed to reduce the weighted unwanted radiation power.

[0014] In the step of designing the pulse shaping filter, frequencies different from the center frequencies of the respective subcarriers in the generated OFDM signal may be used as the center frequencies of the respective subcarriers.

[0015] In the step of designing the pulse shaping filter, frequencies that are close in frequency to the frequency band evaluated as unwanted radiation may be selected from among the center frequencies of the respective subcarriers in the generated OFDM signal and used as the center frequencies of the respective subcarriers.

[0016] In the step of designing the pulse shaping filter, decimated frequencies of the center frequencies of the respective subcarriers in the generated OFDM signal may be selected and used as the center frequencies of the respective subcarriers.

[0017] In the step of designing the pulse shaping filter, different having statistically identical characteristics modulation symbols from the modulation symbols of the respective subcarriers in the generated OFDM signal may be used as the modulation symbols of the respective subcarriers.

[0018] One aspect of the present invention is a program for causing a computer to execute a step of adding a cyclic prefix to a generated OFDM signal, a step of designing a pulse shaping filter, and a step of performing pulse shaping on the OFDM signal to which the cyclic prefix has been added using the designed pulse shaping filter. In the step of designing the pulse shaping filter, The number of OFDM symbols L, the OFDM symbol length Nsym, the sample rate Fs, the s the modulation symbols of the subcarriers a k、l(where a k、l is the k-th input modulation symbol of the l-th OFDM symbol) and s the center frequency of the sub-carrier f k (where f k is the center frequency of the subcarrier corresponding to the k-th input modulation symbol) and the number of subcarriers Nsc, and the FFT size N FFT and the CP length N CP and the pulse shaping filter length N PS and are used to Based on the vector S representing the spectrum of the OFDM signal before pulse shaping calculated according to Equations (5a), (5b), Equation (2), and Equation (3), the vector w representing the filter shape of the pulse shaping filter calculated according to Equation (1), and the matrix B for converting the vector w into the spectrum calculated according to Equations (4a) and (4b), the range of m is calculated such that νm is in the range of the unnecessary radiation band design the pulse shaping filter so as to reduce the unnecessary radiation power. It is a program.

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[0019] One aspect of the present invention includes a CP adding unit that adds a cyclic prefix to the generated OFDM signal, a pulse shaping filter design unit that designs a pulse shaping filter, and a pulse shaping unit that performs pulse shaping on the OFDM signal with the cyclic prefix added using the designed pulse shaping filter. In the pulse shaping filter design unit, The number of OFDM symbols L, the OFDM symbol length Nsym, the sample rate Fs, the s the modulation symbol of the sub-carrier a k、l (where a k、l is the k-th input modulation symbol of the l-th OFDM symbol) and s the center frequency of the sub-carrier f k (where f k is the center frequency of the subcarrier corresponding to the k-th input modulation symbol) and the number of subcarriers Nsc, and the FFT size NFFT and the CP length N CP and the pulse shaping filter length N PS to design the pulse shaping filter so as to reduce the unnecessary radiation power, a wireless transmission device. Based on the vector S representing the spectrum of the OFDM signal before pulse shaping calculated according to Equations (5a), (5b), Equation (2), and Equation (3), the vector w representing the filter shape of the pulse shaping filter calculated according to Equation (1), and the matrix B for converting the vector w into the spectrum calculated according to Equations (4a) and (4b), the range of m is calculated such that νm is in the range of the unnecessary radiation band [Number] [Number] [Number] [Number] [Number] [Effect of the Invention]

[0020] According to the present invention, there is an effect that a signal processing method, a program, and a wireless transmission device suitable for suppressing ACLR and OOBE can be realized. [Brief Description of the Drawings]

[0021]

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Best Mode for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited by the embodiments described below. Further, in the description of the drawings, the same parts are appropriately given the same reference numerals, and duplicate descriptions are omitted as appropriate.

[0023] (Embodiment 1) FIG. 1 is a configuration diagram of a wireless transmission device according to Embodiment 1. The wireless transmission device 100 is a device that wirelessly transmits an OFDM signal in the W-OFDM system, and includes a data providing unit 10, a parameter providing unit 20, an OFDM signal generating unit 30, a CP adding unit 40, a pulse shaping unit 50, a digital / analog converter (DAC) 60, a wireless transmission unit 70, and a pulse shaping filter design unit 80.

[0024] The OFDM signal generating unit 30 includes a serial / parallel conversion unit 31, an inverse fast Fourier transform (IFFT) unit 32, and a parallel / serial conversion unit 33.

[0025] In the wireless transmission device 100, functional units such as the data providing unit 10, the parameter providing unit 20, the OFDM signal generating unit 30, the CP adding unit 40, the pulse shaping unit 50, and the pulse shaping filter design unit 80 are configured by, for example, a microcomputer including a processor and a memory. These functional units are realized by the cooperation of hardware and software, for example, by the processor executing a program read from the memory.

[0026] The processor is, for example, a CPU (Central Processing Unit) or a DSP (Digital Signal Processor), and performs arithmetic processing. The memory can be configured using semiconductor memory that provides a work space for the processor to perform arithmetic processing or stores programs and data. The semiconductor memory is, for example, RAM (Random Access Memory), ROM (Read Only Memory), EPROM (Erasable Programmable Read Only Memory), etc.

[0027] Hereinafter, the functions of each functional unit and the configurations and functions of the DAC60 and the wireless transmission unit 70 will be described.

[0028] The data providing unit 10 acquires, as data regarding the OFDM signal, the input modulation symbol a k、l and the subcarrier frequency f k and provides them to the OFDM signal generation unit 30 and the pulse shaping filter design unit 80. Here, a k、l is the k-th input modulation symbol of the l-th OFDM symbol, and f k is the center frequency of the subcarrier corresponding to the k-th input modulation symbol. The range of k is represented as 0 ≦ k < Nc using the number of subcarriers Nc. The range of l is represented as 0 ≦ l < L using the number of symbols L. Note that, for example, orthogonal modulation symbols such as QPSK (Quadrature Phase Shift Keying) are common as input modulation symbols.

[0029] The parameter providing unit 20 provides the FFT size N FFT the CP length N CP and the pulse shaping filter length N PS to the pulse shaping filter design unit 80, and provides the FFT size N FFT to the S / P conversion unit 31 of the OFDM signal generation unit 30. These parameters are stored in the memory and are read out as appropriate.

[0030] The OFDM signal generation unit 30 executes the steps of generating an OFDM signal as follows. First, the S / P conversion unit 31 uses the input modulation symbol a k、l and the subcarrier frequency f k and the FFT size N FFT to arrange the input modulation symbols on the frequency axis to generate frequency data and transmit it to the IFFT unit 32.

[0031] The IFFT unit 32 converts the frequency data into time-axis data and transmits it to the P / S conversion unit 33.

[0032] The P / S conversion unit 33 rearranges the time-axis data in the order of time to generate an OFDM signal and transmits it to the CP addition unit 40. At this time, the sample rate of the time-axis data is Fs.

[0033] The CP addition unit 40 executes the step of adding a CP to the OFDM signal generated by the OFDM signal generation unit 30.

[0034] The pulse shaping filter design unit 80 uses the input modulation symbol a k、l and the subcarrier frequency f k and the FFT size N FFT and the CP length N CP and the pulse shaping filter length N PS to execute the step of designing a pulse shaping filter and transmits the designed pulse shaping filter to the pulse shaping unit 50. Note that the design of the filter means determining in advance the desired characteristics and structure of the filter and determining the parameters of the filter to realize the desired characteristics. That is, the pulse shaping filter design unit 80 calculates the coefficients of the pulse shaping filter.

[0035] The pulse shaping unit 50 executes the step of performing pulse shaping on the OFDM signal to which the CP addition unit 40 has added a CP using the pulse shaping filter designed by the pulse shaping filter design unit 80. The pulse shaping unit 50 transmits the OFDM signal (W-OFDM mode signal) subjected to pulse shaping to the DAC 60.

[0036] The DAC 60 converts the OFDM signal subjected to pulse shaping from a digital signal into an analog signal and transmits it to the wireless transmission unit 70.

[0037] The wireless transmission unit 70 includes a power amplifier, an antenna, a filter, etc., and wirelessly transmits the OFDM signal converted into an analog signal.

[0038] (Operation of the CP addition unit) Next, the operation of the CP addition unit 40 will be described in detail with reference to FIG. 2. First, an OFDM signal (time-axis data) having a length of the FFT size N FFT is input to the CP addition unit 40. Subsequently, the CP addition unit 40 copies data of only the CP length N CP from the temporally rear side of the time-axis data and adds it to the temporally front side of the time-axis data. Therefore, the CP addition unit 40 outputs time-axis data having a length of (N FFT +N CP ) as the OFDM signal with CP added to the pulse shaping unit 50.

[0039] (Operation of the pulse shaping unit) Next, the operation of the pulse shaping unit 50 will be described in detail with reference to FIG. 3. The pulse shaping unit 50 first copies data of only the pulse shaping filter length N FFT +N CP from the temporally rear side with respect to the time-axis data having a length of (N PS ) input from the CP addition unit 40 and adds it to the temporally front side of the time-axis data. Subsequently, the copied portion is multiplied by the left pulse shaping filter w p . Subsequently, the original copied portion is multiplied by the right pulse shaping filter. The right pulse shaping filter is (1 - w p ) with respect to the left pulse shaping filter w p) is represented by. Subsequently, the part multiplied by the right pulse shaping filter and the part multiplied by the left pulse shaping filter of the next symbol are added to obtain the output signal to DAC60. Although not shown in the figure, the part multiplied by the left pulse shaping filter is added to the part multiplied by the right pulse shaping filter of the previous symbol to obtain the output signal to DAC60.

[0040] Note that in the above, first, data of only the pulse shaping filter length N PS is copied from the later side in time and added to the front side in time of the time axis data. However, data of only the pulse shaping filter length N PS may be copied from the front side in time and added to the back side in time of the time axis data, or the data lengths to be added may be copied from both the front side and the back side so that the total is the pulse shaping filter length N PS and added to both the front side and the back side.

[0041] (Operation of Pulse Shaping Filter Design Section) Next, the operation of the pulse shaping filter design section 80 will be described in detail. In the step where the pulse shaping filter design section 80 designs the pulse shaping filter, the pulse shaping filter is designed so as to reduce unnecessary radiated power. This will be described in detail using mathematical formulas below.

[0042] First, a vector w obtained by vectorizing the pulse shaping filter w p is defined as in the following equation (1). The vector w can be said to be a vector w representing the filter shape of the pulse shaping filter w p . [Number]

[0043] The frequency ν m for evaluating the spectrum of the OFDM signal is defined as in the following equation (2). The range that m can take is 0 ≤ m < LNs. Ns is the OFDM symbol length. Also, the range that ν m can take is -Fs / 2 ≤ ν m<Fs / 2.

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[0044] Sub - carrier frequency f k and the frequency ν for evaluating the unnecessary radiation power m The difference from is normalized by the sampling rate Fs and converted to an angular frequency variable ω km is defined as in the following equation (3).

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[0045] Matrix B and the element b constituting matrix B m,p are defined as in the following equations (4a) and (4b). Matrix B is a matrix for converting the pulse - shaping filter into a spectrum, and it can be said that Bw is a vector indicating the change amount from before pulse - shaping to after applying pulse - shaping with w to the spectrum of the OFDM signal.

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[0046] Here, the range of m is the range where ν m becomes the unnecessary radiation band. For example, in the case equivalent to LTE (Long Term Evolution) 20 MHz, each parameter is as follows.

[0047] ·L (number of OFDM symbols): 140 ·Fs (sampling rate): 30.72 Msps ·a k、l (input modulation symbol): QPSK ·f k (sub - carrier frequency): 15 kHz interval ·Nsc (number of sub - carriers): 1200 ·N FFT (FFT size): 2048 ·N CP (CP length): 144 ·Nsym( O FDM symbol length): 2192 ·N PS (Pulse shaping filter length): 16

[0048] Since it is a parameter equivalent to LTE 20 MHz, the signal band is in the range of -10 MHz to +10 MHz. The bands to be evaluated as unwanted radiation are the bands below -10 MHz and above +10 MHz. Specifically, they are from -15.36 MHz to -10 MHz and from +10 MHz to +15.36 MHz. Since LNsym = 306880, the range of m for which νm becomes the unwanted radiation band is from 0 to 53544 and from 253336 to 306879.

[0049] Next, the vector S and the elements Sm that make up the vector S are defined as in the following equations (5a) and (5b). The vector S can be said to be a vector representing the spectrum of the OFDM signal before pulse shaping. Here, the range of m is the same as in the case of the matrix B, where ν m is the range that becomes the unwanted radiation band.

Equation

[0050] From the above definitions, based on the matrix B, the vector w, and S, the unwanted radiation power is represented by the following equation (6). Here, ||a||2 is the 2-norm of the vector a, and ||a||2 2 is the sum of the squares of the elements of the vector a.

Equation

[0051] The pulse shaping filter design unit 80 designs the pulse shaping filter so that the unwanted radiation power represented by equation (6) is reduced compared to the case where no pulse shaping filter is applied. For example, the pulse shaping filter design unit 80 designs the pulse shaping filter so that the unwanted radiation power is reduced to be below the value determined by the wireless communication standard or minimized.

[0052] When not minimizing the radiated power, w may be designed such that the squared norm shown in Equation (6) is minimized. Let such w be w opt Then, w opt is represented by the following Equation (7). Here, A H is the complex conjugate transpose matrix of matrix A, and A -1 is the inverse matrix of matrix A.

[0053]

Equation

[0054] In the wireless transmission device 100 according to Embodiment 1 configured as described above, as a signal processing method, the CP addition unit 40 executes a step of adding CP to the OFDM signal generated by the OFDM signal generation unit 30, the pulse shaping filter design unit 80 executes a step of designing a pulse shaping filter, and the pulse shaping unit 50 executes a step of performing pulse shaping on the OFDM signal to which CP has been added using the pulse shaping filter designed by the pulse shaping filter design unit 80. And in the step of designing the pulse shaping filter, the pulse shaping filter design unit 80 uses a k、l which is the modulation symbol of each subcarrier, f k which is the center frequency of each subcarrier, the FFT size N FFT the CP length N CP and the pulse shaping filter length N PS to design the pulse shaping filter so as to reduce the unnecessary radiated power. Thereby, unnecessary radiation is reduced, and suitable pulse shaping can be realized from the viewpoint of suppressing ACLR and OOBE. As a result, for example, inter-symbol interference can be minimized while satisfying the required unnecessary radiation performance.

[0055] Next, as an example, the power spectrum of the OFDM signal in the W-OFDM system generated by the wireless transmission device 100 according to the first embodiment is shown in FIG. 4. In FIG. 4, as an example, in order to minimize the unnecessary radiation power, w is designed such that the square norm represented by Equation (6) is minimized. Further, in FIG. 4, the power spectrum before pulse shaping and the power spectrum in the case of using a raised cosine as a pulse shaping filter (comparative example) are also shown. The raised cosine is represented by the following Equation (8). Further, as parameters, the parameters corresponding to LTE 20 MHz described above are used.

Equation

[0056] As shown in FIG. 4, it can be seen that in both the example and the comparative example, unnecessary radiation is reduced and ACLR and OOBE are suppressed as compared with the power spectrum before pulse shaping. Further, it can be seen that the power spectrum in the case of using the raised cosine of the comparative example has relatively high unnecessary radiation around +10 MHz to +11 MHz, but the unnecessary radiation can be reduced in the example.

[0057] Note that in the range of +11 MHz or higher, the unnecessary radiation is smaller in the comparative example than in the example. However, since the contribution to the unnecessary radiation power in the range of +10 MHz to +15.36 MHz is dominated by the component around +10 MHz to +11 MHz, it can be said that the example has a higher effect of reducing the unnecessary radiation power.

[0058] Note that in the description of the first embodiment above, there is no restriction on the shape of the pulse shaping filter, but the shape of the pulse shaping filter that reduces unnecessary radiation may be designed after imposing various restrictions.

[0059] For example, by restricting the pulse shaping filter to a filter with real components, it is possible to reduce the unnecessary radiation while reducing the computational amount in the pulse shaping unit 50.

[0060] Further, for example, by restricting the pulse shaping filter to a filter having a temporally point-symmetric shape, the inter-symbol interference to the previous symbol and the inter-symbol interference to the next symbol can be made comparable, so that unnecessary radiation can be reduced while obtaining stable communication performance.

[0061] Furthermore, for example, by restricting the pulse shaping filter to a filter having a real component and a temporally point-symmetric shape, both of the above effects can be obtained.

[0062] Also, when reducing the unnecessary radiation power, the pulse shaping filter may be designed to reduce the weighted unnecessary radiation power. The weighted unnecessary radiation power is represented by, for example, the following formula (9a), and w that minimizes this is opt represented by the following formula (9b). Here, the matrix C is a diagonal matrix for weighting, and the value of the element (m, m) gives the weight at the frequency number m. [Number]

[0063] For example, when the required value of unnecessary radiation varies depending on the frequency, if the weight is increased in the frequency region where it is necessary to significantly suppress unnecessary radiation, unnecessary radiation can be efficiently suppressed. Or, if the weight is reduced in the frequency region where the unnecessary radiation can be suppressed by the wireless transmission unit 70 in the wireless transmission device 100 or the wireless circuit connected to the subsequent stage of the wireless transmission device 100, and the weight is increased in the frequency region where the unnecessary radiation is not suppressed, the unnecessary radiation can be efficiently suppressed in combination with the wireless transmission unit 70 and the subsequent wireless circuit.

[0064] (Embodiment 2) FIG. 5 is a configuration diagram of a wireless transmission device according to Embodiment 2. This wireless transmission device 100A has a configuration in which a design subcarrier frequency providing unit 90A is added to the configuration of the wireless transmission device 100 according to Embodiment 1. Below, the differences from the wireless transmission device 100 will mainly be described.

[0065] In the wireless transmission device 100A, the pulse shaping filter design unit 80 designs a pulse shaping filter using the design sub-carrier frequency provided by the design sub-carrier frequency providing unit 90A.

[0066] The design sub-carrier frequency is different from the sub-carrier frequency (OFDM signal generation sub-carrier frequency) used by the data providing unit 10 to provide to the OFDM signal generation unit 30 to generate an OFDM signal. For example, it constitutes a subset of the OFDM signal generation sub-carrier frequency. That is, the number of design sub-carrier frequencies is less than the number of sub-carrier frequencies provided by the data providing unit 10. Such design sub-carrier frequencies are stored in a memory and are read out and used as appropriate. In this case, when the pulse shaping filter design unit 80 calculates b in Equation (4b) m,p and Sm in Equation (5b), the summation calculation with respect to k is performed only within the range of the subset. As a result, b m,p and the calculation cost of Sm can be reduced.

[0067] For example, the design sub-carrier frequency can be a subset composed of sub-carrier numbers that are frequency-close to the frequency band evaluated as unnecessary radiation. That is, in the step of designing the pulse shaping filter, as the center frequency of each sub-carrier, a frequency that is frequency-close to the frequency band evaluated as unnecessary radiation can be selected and used from among the center frequencies of each sub-carrier in the generated OFDM signal. b m,p And the contribution of each sub-carrier to Sm is small when ω km is large. Therefore, even without considering sub-carriers that are far from the frequency band evaluated as unnecessary radiation in terms of frequency, the influence on the calculation results of b m,p and Sm is small. As a result, the calculation cost of b m,p and Sm can be reduced.

[0068] For example, the subcarrier frequency for design can be obtained by thinning out the subcarrier frequencies for OFDM signal generation at appropriate intervals. That is, as the center frequency of each subcarrier, a frequency obtained by thinning out the center frequencies of the subcarriers in the generated OFDM signal can be selected and used. Since the contribution degrees of adjacent subcarriers to the frequency band for evaluating unnecessary radiation are similar, even if only representative subcarrier numbers are used, b m,p and the influence on the calculation result of Sm is small. As a result, b m,p and the calculation cost of Sm can be reduced.

[0069] Furthermore, for example, the subcarrier frequency for design is a subset composed of subcarrier numbers that are close in frequency to the frequency band evaluated as unnecessary radiation, and can be obtained by thinning out the subcarrier frequencies for OFDM signal generation at appropriate intervals. As a result, b m,p and the calculation cost of Sm can be further reduced.

[0070] (Embodiment 3) FIG. 6 is a configuration diagram of a wireless transmission device according to Embodiment 3. This wireless transmission device 100B has a configuration in which a modulation symbol providing unit 90B for design is added to the configuration of the wireless transmission device 100 according to Embodiment 1. Below, mainly the differences from the wireless transmission device 100 will be described.

[0071] In the wireless transmission device 100B, the pulse shaping filter design unit 80 designs a pulse shaping filter using the modulation symbol for design provided by the modulation symbol providing unit 90B for design. This modulation symbol for design uses a symbol having statistically the same characteristics as the input modulation symbol provided by the data providing unit 10 to the OFDM signal generation unit 30 to generate an OFDM signal. Such a modulation symbol for design is stored in a memory and is read out and used as appropriate. Thereby, even if the input modulation symbol changes from moment to moment, the modulation symbol for design can be fixed, so that the frequency of the pulse shaping filter design unit 80 designing the pulse shaping filter can be reduced.

[0072] As a specific example of the modulation symbol for design, for example, in the case of LTE, a test model defined by 3GPP (3rd Generation Partnership Project), more specifically, E-TM1.1 with the same bandwidth as the input modulation symbol can be used. This E-TM1.1 is a signal used for the evaluation of unnecessary radiation and has statistically the same characteristics as the LTE transmission signal, so it can be suitably used in the pulse shaping filter design unit 80.

[0073] Also, as the modulation symbol for design, a QPSK modulation symbol generated using random numbers can be used. In the case of LTE, BPSK, QPSK, 16QAM, etc. are mixed in the input modulation symbols, but even if all the modulation symbols for design are QPSK, b m,p And since the statistical properties in calculating Sm do not change, it can be suitably used in the pulse shaping filter design unit 80.

[0074] (Embodiment 4) FIG. 7 is a configuration diagram of a wireless transmission device according to Embodiment 4. This wireless transmission device 100C has a configuration in which a modulation symbol providing unit 90B for design is added to the configuration of the wireless transmission device 100A according to Embodiment 2.

[0075] In the wireless transmission device 100C, the pulse shaping filter design unit 80 designs a pulse shaping filter using the design subcarrier frequency provided by the design subcarrier frequency providing unit 90A and the modulation symbol for design provided by the modulation symbol providing unit 90B for design. Thereby, similar to the wireless transmission devices 100A and 100B, b m,p The calculation cost of and Sm can be reduced, and the frequency at which the pulse shaping filter design unit 80 designs the pulse shaping filter can be decreased.

[0076] Also, in the wireless transmission device 100C, by using the design sub-carrier frequency and the design modulation symbol, it is also possible to design a pulse shaping filter that reduces or minimizes unnecessary radiation in advance. In this case, the pulse shaping filter design unit 80 stores the shape of the pulse shaping filter designed with various parameters in the memory, and may transmit the appropriate shape of the pulse shaping filter and the pulse shaping filter length to the pulse shaping unit 50 according to the parameters of the generated OFDM signal.

[0077] Note that the present invention is not limited by the above-described embodiments. Those configured by appropriately combining the above-described components are also included in the present invention. Further, additional effects and modification examples can be easily derived by those skilled in the art. Therefore, a broader aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible.

Explanation of Reference Numerals

[0078] 10: Data providing unit 20: Parameter providing unit 30: OFDM signal generation unit 31: S / P conversion unit 32: IFFT unit 33: P / S conversion unit 40: CP adding unit 50: Pulse shaping unit 60: DAC 70: Wireless transmission unit 80: Pulse shaping filter design unit 90A: Design sub-carrier frequency providing unit 90B: Design modulation symbol providing unit 100, 100A, 100B, 100C: Wireless transmission device

Claims

1. A step of adding a cyclic prefix to the generated OFDM signal; A step of designing a pulse shaping filter; A step of performing pulse shaping on the OFDM signal with the cyclic prefix added, using the designed pulse shaping filter; comprising: In the step of designing the pulse shaping filter, the number of OFDM symbols L, the OFDM symbol length Nsym, the sample rate Fs, the modulation symbol ak,l of the subcarrier (where ak,l is the k-th input modulation symbol of the l-th OFDM symbol), the center frequency fk of the subcarrier (where fk is the center frequency of the subcarrier corresponding to the k-th input modulation symbol), the number of subcarriers Nsc, the FFT size NFFT, the CP length NCP, the pulse shaping filter length NPS, are used to design the pulse shaping filter so as to reduce the unnecessary radiation power calculated based on the vector S representing the spectrum of the OFDM signal before pulse shaping, calculated according to equations (5a), (5b), equation (2), and equation (3), the vector w representing the filter shape of the pulse shaping filter, calculated according to equation (1), and the matrix B for converting the vector w into a spectrum, calculated according to equations (4a) and (4b), where the range of m is calculated as the range in which νm becomes the unnecessary radiation band A signal processing method. 【Number 1】 【Number 2】 【Mathematics 3】 【Number 4】 【Number 5】

2. In the step of designing the pulse shaping filter, design the pulse shaping filter so as to minimize the unnecessary radiation power The signal processing method according to claim 1.

3. The pulse shaping filter is a filter with real components, a filter with a temporally point-symmetric shape, or a filter with real components and a temporally point-symmetric shape The signal processing method according to claim 1 or 2.

4. In the step of designing the pulse shaping filter, design the pulse shaping filter so as to reduce the weighted unnecessary radiation power The signal processing method according to any one of claims 1 to 3.

5. In the step of designing the pulse shaping filter, use a frequency different from the center frequency of each subcarrier in the generated OFDM signal as the center frequency of each subcarrier The signal processing method according to any one of claims 1 to 4.

6. In the step of designing the pulse shaping filter, as the center frequency of each sub-carrier, a frequency that is close in frequency to the frequency band evaluated as unnecessary radiation is selected from among the center frequencies of the respective sub-carriers in the generated OFDM signal and used. The signal processing method according to any one of claims 1 to 4.

7. In the step of designing the pulse shaping filter, as the center frequency of each sub-carrier, a frequency obtained by thinning out the center frequencies of the respective sub-carriers in the generated OFDM signal is selected and used. The signal processing method according to any one of claims 1 to 4.

8. In the step of designing the pulse shaping filter, as the modulation symbol of each sub-carrier, a modulation symbol that is different from the modulation symbol of each sub-carrier in the generated OFDM signal but has statistically the same characteristics is used. The signal processing method according to any one of claims 1 to 7.

9. A step of adding a cyclic prefix to the generated OFDM signal, A step of designing a pulse shaping filter, A step of performing pulse shaping on the OFDM signal to which the cyclic prefix is added using the designed pulse shaping filter, A program for causing a computer to execute, In the step of designing the pulse shaping filter, The number of OFDM symbols L, The OFDM symbol length Nsym, The sample rate Fs, The modulation symbol ak,l of the sub-carrier (where ak,l is the k-th input modulation symbol of the l-th OFDM symbol), The center frequency fk of the sub-carrier (where fk is the center frequency of the sub-carrier corresponding to the k-th input modulation symbol), The number of sub-carriers Nsc, The FFT size NFFT, The CP length NCP, The pulse shaping filter length NPS, are used, Based on the vector S representing the spectrum of the OFDM signal before pulse shaping, calculated according to equations (5a), (5b), equation (2), and equation (3), the vector w representing the filter shape of the pulse shaping filter, calculated according to equation (1), and the matrix B for converting the vector w into a spectrum, calculated according to equations (4a) and (4b), the range of m is calculated as the range in which νm becomes the unnecessary radiation band, and the pulse shaping filter is designed so as to reduce the unnecessary radiation power. Program. 【Number 6】 【Number 7】 【Number 8】 【Number 9】 【Number 10】

10. A CP adding unit that adds a cyclic prefix to the generated OFDM signal; A pulse shaping filter design unit that designs a pulse shaping filter; A pulse shaping unit that performs pulse shaping on the OFDM signal to which the cyclic prefix is added, using the designed pulse shaping filter; comprising In the pulse shaping filter design unit, the number of OFDM symbols L, the OFDM symbol length Nsym, the sampling rate Fs, the modulation symbol ak,l of the subcarrier (where ak,l is the k-th input modulation symbol of the l-th OFDM symbol), the center frequency fk of the subcarrier (where fk is the center frequency of the subcarrier corresponding to the k-th input modulation symbol), the number of subcarriers Nsc, the FFT size NFFT, the CP length NCP, the pulse shaping filter length NPS, are used to design the pulse shaping filter so as to reduce the unnecessary radiation power calculated such that the range of m is the range where νm becomes the unnecessary radiation band, based on the vector S representing the spectrum of the OFDM signal before pulse shaping, calculated according to formulas (5a), (5b), formula (2), and formula (3), the vector w representing the filter shape of the pulse shaping filter, calculated according to formula (1), and the matrix B for converting the vector w into a spectrum, calculated according to formulas (4a) and (4b); A wireless transmission device. 【Number 11】 【Number 12】 【Number 13】 【Number 14】 【Number 15】

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