Information processing device, information processing method, and information processing program

Abstract

The objective is to provide an information processing device, an information processing method, and an information processing program that can suppress PAPR and suppress the increase in EVM. [Solution] The information processing device is an information processing device that suppresses the peak power to average power ratio of a signal, and comprises a determination processing unit that determines whether or not the amplitude of the input signal exceeds a preset threshold, and a PC processing unit that performs peak canceling processing on the excess signal determined to have an amplitude exceeding the threshold to reduce the amplitude exceeding the threshold, and the PC processing unit comprises a filter unit that performs filtering to remove the frequency band component of the excess signal from the input signal.

Description

[Technical Field]

[0001] The present invention relates to an information processing device, an information processing method, and an information processing program that suppress the peak power to average power ratio of a signal. [Background technology]

[0002] In conventional wireless communication devices, it is known that the peak-to-average power ratio (PAPR) of the modulated signal is suppressed. By suppressing PAPR, the maximum input voltage when inputting the signal to the power amplifier can be reduced, thereby improving energy utilization efficiency.

[0003] Clipping and filtering (hereinafter referred to as "C&F") is a known method for suppressing PAPR (see, for example, Non-Patent Document 1). C&F is a technique that replaces the amplitude of an input signal with a constant value if it exceeds a set threshold. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Xiaodong Li and Leonard J. Cimini, Jr, “Effects of Clipping and Filtering on the Performance of OFDM”, IEEE Communication Letters, Vol.2, No. 5, MAY 1998 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in conventional C&F (Cross-and-Flash) systems, clipping is performed regardless of the frequency bandwidth of the modulated signal, which increases the EVM (Error Vector Magnitude), and in some cases, the receiver may not be able to correctly recover the data during demodulation.

[0006] The present invention is based on the above-mentioned problems and aims to provide an information processing device, an information processing method, and an information processing program that can suppress PAPR and suppress the increase in EVM. [Means for solving the problem]

[0007] The information processing device according to the present invention is an information processing device that suppresses the peak power to average power ratio of a signal, and comprises a determination processing unit that determines whether or not the amplitude of an input signal exceeds a preset threshold, and a PC processing unit that performs peak canceling processing on the excess signal determined to have an amplitude exceeding the threshold to reduce the amplitude exceeding the threshold, wherein the PC processing unit includes a filter unit that performs filtering to remove the frequency band component of the excess signal from the input signal.

[0008] Furthermore, the information processing method according to the present invention is an information processing method for suppressing the peak power to average power ratio of a signal, comprising: a determination processing step of determining whether or not the amplitude of an input signal exceeds a preset threshold; and a PC processing step of reducing the amplitude exceeding the threshold for the excess signal that has been determined to exceed the threshold, wherein the PC processing step includes a filtering step of removing the frequency band component of the excess signal from the input signal.

[0009] Further, an information processing program according to the present invention is an information processing program for suppressing a peak-to-average power ratio of a signal, which causes a computer to execute: a determination processing step of determining whether an amplitude of an input signal exceeds a preset threshold; and a PC processing step of performing peak canceling processing for reducing an amplitude exceeding the threshold on an excess signal determined to have an amplitude exceeding the threshold, wherein the PC processing step includes a filtering step of removing a frequency band component of the excess signal from the input signal. [Advantages of the Invention]

[0010] According to the information processing apparatus, information processing method, and information processing program of the present invention, in PC processing, filtering for removing frequency band components of an excess signal from an input signal is performed, whereby PAPR can be suppressed and an increase in EVM can be suppressed. [Brief Description of Drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an information processing apparatus according to a first embodiment. [Figure 2] 2 is a flowchart showing a flow of PAPR suppression processing in the first embodiment. [Figure 3] 3 is a diagram illustrating a first arithmetic processing performed by a first arithmetic unit according to the first embodiment. [Figure 4] 4 is a diagram illustrating a second arithmetic processing performed by a second arithmetic unit according to the first embodiment. [Figure 5] 5 is a diagram for explaining the effect of the information processing apparatus according to the first embodiment in the frequency domain. [Figure 6] 6 is a diagram for explaining the operation of an information processing apparatus according to a comparative example in the frequency domain. [Figure 7] 7 is a table showing simulation results of EVM of the comparative example and the first embodiment with respect to a desired PAPR suppression amount. [Figure 8] 8 is a graph of the simulation results of FIG. 7. [Figure 9]FIG. 1 is a schematic configuration diagram of an information processing apparatus according to a second embodiment. [Figure 10] FIG. 2 is a diagram for explaining clipping processing by a replacement unit according to the second embodiment. [Figure 11] FIG. 3 is a flowchart showing an operation flow of the information processing apparatus according to the second embodiment. [Figure 12] Table 1 shows simulation results of actual PAPR suppression amounts of the first embodiment and the second embodiment with respect to a desired PAPR suppression amount. [Figure 13] FIG. 12 is a graph of the simulation results of FIG. 12. [Figure 14] Table 2 shows simulation results of EVM of a comparative example, the first embodiment, and the second embodiment with respect to a desired PAPR suppression amount. [Figure 15] FIG. 14 is a graph of the simulation results of FIG. 14. [Figure 16] FIG. 4 is a diagram showing time-domain waveforms of single-carrier modulation and multi-carrier modulation. [Figure 17] FIG. 5 is a schematic configuration diagram of an information processing apparatus that performs PAPR suppression processing according to a conventional technology. DETAILED DESCRIPTION OF THE INVENTION

[0012] First, description will be given of suppression of peak to average power ratio (hereinafter referred to as "PAPR") in a signal. When transmitting information to a counterpart via wireless communication, information is superimposed on a carrier wave in order to prevent interference and use communication in a desired band. Superimposing information on a carrier wave is called "modulation", and obtaining information from a modulated waveform is called "demodulation". Modulation schemes are broadly divided into single-carrier modulation and multi-carrier modulation. Single-carrier modulation is a modulation scheme that uses a narrowband signal with a single frequency, and examples include ASK, PSK, and FSK. Multi-carrier modulation is a modulation scheme that uses a plurality of frequency components, and examples include FDM and OFDM. In the case of multi-carrier modulation, since it is a set of carriers with different frequencies, the amplitude in the time direction approximates a random signal.

[0013] Figure 16 shows time-domain waveforms for single-carrier modulation and multi-carrier modulation. Figure 16(a) shows the time-domain waveform signal for single-carrier modulation, and Figure 16(b) shows the time-domain waveform signal for multi-carrier modulation. The time-domain waveform signal for multi-carrier modulation is, for example, an OFDM signal. In Figure 16, the RMS (Root Mean Square) value and peak value of each signal are shown. In this case, the PARP, which is the ratio of the peak value to the RMS value, is expressed by equation (1).

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[0014] In equation (1), x(kT) is the time-series data of the signal, k is the sample number, T is the sampling interval, max[] is the maximum value calculation, and RMS[] is the root mean square calculation. From the time-domain waveforms of the single-carrier modulated signal and the multi-carrier modulated signal in Figure 16, it can be seen that the PAPR increases for the multi-carrier modulated signal compared to the single-carrier modulated signal. When PAPR increases, it is necessary to increase the dynamic range of the amplifier for transmission, which leads to an increase in the overall size, cost, and power consumption of the signal transmitter. For this reason, several methods have been proposed to suppress PAPR. The simplest method is clipping and filtering (hereinafter referred to as "C&F"). This is a method in which, if the amplitude of the input signal exceeds a set threshold, it is replaced with a constant value.

[0015] Figure 17 is a schematic diagram of an information processing device 500 that performs PAPR suppression processing according to the prior art. The information processing device 500 is a device that performs threshold exceedance determination processing, waveform cutting processing, and bandwidth limiting processing on a signal to which PAPR is to be suppressed (hereinafter referred to as the "input signal") input to the input terminal 51, and outputs a PAPR-suppressed signal from the output terminal 52. As shown in Figure 17, the information processing device 500 includes a determination unit 501 and a distribution unit 502 that perform threshold exceedance determination processing, a replacement unit 503 that performs waveform cutting processing, and a BPF 504 that performs bandwidth limiting processing.

[0016] The determination unit 501 determines whether the amplitude of the input signal input to the input terminal 51 exceeds a preset threshold. The distribution unit 502 distributes the output destinations of signals whose amplitude exceeds the threshold (hereinafter referred to as "excess signals") and signals whose amplitude is below the threshold (hereinafter referred to as "non-excess signals") according to the determination result of the determination unit 501. Specifically, the distribution unit 502 outputs non-excess signals, when the amplitude of the input signal is below the threshold, to the output terminal 52, bypassing the replacement unit 503 and the BPF 504. The distribution unit 502 also outputs excess signals, when the amplitude of the input signal exceeds the threshold, to the replacement unit 503. The replacement unit 503 performs a replacement process on the excess signal, replacing the amplitude exceeding the threshold with a certain value, such as the threshold. The signal after replacement by the replacement unit 503 (hereinafter referred to as "clip signals") y p2 (kT) can be expressed by the following equation (2).

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[0017] In equation (2), A is a preset threshold, x(kT) is the excess signal input to the substitution unit 503, and PAPR des is the desired PAPR. The clipping signal y output from the replacement unit 503 p2 (kT) is input to BPF504.

[0018] The BPF504 is a band-pass filter that takes in the input clipping signal yp2 Filtering expressed by formulas (3), (4), and (5) is performed on (kT) to obtain a filtered signal y with adjacent channel leakage power (hereinafter referred to as "ACP") suppressed p3 (kT) is output.

Mathematical Expression

Mathematical Expression

Mathematical Expression

[0019] In formula (3), * denotes a convolution operation, and h BPF (kT) is a filter coefficient in the time domain. In formula (4), N is the number of samples, n is a sample number represented by an integer, and H BPF (n / NT) is a frequency-domain filter coefficient. In formula (5), f low is the lower band frequency of the input signal input to input terminal 51, and f high is the upper band frequency of the input signal input to input terminal 51, and f is the frequency of the clipped signal. In formula (5), the characteristics of the BPF are set in accordance with a desired frequency band. In formula (4), the frequency-domain filter coefficients generated in formula (5) are converted into time-domain filter coefficients by inverse Fourier transform. In formula (3), the impulse response of the filter coefficients generated in formula (4) and the clipped signal y p2 (kT) are convolved.

[0020] The BPF504 can suppress the ACP generated by the substitution unit 503. ACP is the power that leaks into the frequency band adjacent to the desired frequency band. An increase in ACP can cause problems such as interference to other channels. By filtering with the BPF504, the increase in ACP resulting from C&F can be suppressed. However, filtering by the BPF504 may increase PAPR. As a countermeasure, it is known that the output of the BPF504 is returned to the input of the determination unit 501, and the processing in the distribution unit 502, substitution unit 503, and BPF504 is performed again. By repeating this process, the increase in ACP can be suppressed while gradually approaching the desired PAPR value.

[0021] As a conventional technique, methods are known that apply the above C&F to shorten processing time. In addition, as a PAPR suppression measure in underwater acoustic communication, a method that removes filtering from C&F is also known. When performing communication using sound waves underwater, unlike communication using electromagnetic waves on land, there are no legal restrictions on bandwidth, so it is not necessary to set up a BPF 504 in Figure 17 for filtering. In this case, PAPR does not increase, so recursive processing is unnecessary, and the desired PAPR can be achieved by performing the substitution processing of the substitution unit 503 in Figure 17 only once. In reality, the transmission power is consumed by the ACP generated by the substitution unit 503, and the transmission power level in the frequency band of the carrier modulation signal decreases, so a low-pass filter (LPF) or the like is sometimes set up after the substitution unit 503 to limit the transmission frequency band. That is, by limiting the transmission frequency band with an LPF, the power used during transmission can be concentrated in the frequency band of the carrier modulation signal. When applying an LPF, the BPF 504 in Figure 17 should be replaced with an LPF.

[0022] In the conventional information processing device 500 described above, the Error Vector Magnitude (EVM) increases because clipping occurs regardless of the frequency band of the carrier modulation signal. When the EVM increases, there is a risk that the receiver will not be able to correctly recover the data during demodulation. A supplementary explanation of EVM is given below. EVM represents the amount of difference between the amplitude and phase information of the transmitted signal and the amplitude and phase information of the received signal. EVM is generally calculated using the root sum of squares (Root Sum Square) based on multiple data, as shown in equation (6). In equation (6), Dem(n) is the received complex signal and Ref(n) is the transmitted complex signal.

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[0023] Embodiment 1. Next, the information processing device 100 in Embodiment 1 will be described. The information processing device 100 in Embodiment 1 is a device that performs threshold exceedance determination processing and peak cancellation (PC) processing on a signal to which PAPR is to be suppressed (hereinafter referred to as the "input signal") input to the input terminal 101, and outputs a PAPR-suppressed signal from the output terminal 102. The input signal in Embodiment 1 is, for example, a multi-carrier modulated OFDM signal. PC processing is a process that suppresses PAPR by reducing the amplitude of the input OFDM signal that exceeds a preset threshold.

[0024] Figure 1 is a schematic diagram of the information processing device 100 according to Embodiment 1. The information processing device 100 includes a computer equipped with a processor such as a CPU and memory, a dedicated processing circuit such as an ASIC or FPGA, or both. As shown in Figure 1, the information processing device 100 includes, as functional units, a determination processing unit 1 that performs threshold exceedance determination processing and a PC processing unit 2 that performs PC processing. The determination processing unit 1 includes a determination unit 11 and a distribution unit 12. The PC processing unit 2 includes a replacement unit 21, a first calculation unit 22, a filter unit 23, and a second calculation unit 24. Each functional unit of the information processing device 100 is realized by reading and executing an information processing program stored in memory, or by a processing circuit corresponding to each functional unit.

[0025] The determination unit 11 determines whether the amplitude of the input signal input to the input terminal 101 exceeds a preset threshold. The distribution unit 12 distributes the output destinations of signals whose amplitude exceeds the threshold (hereinafter referred to as "excess signals") and signals whose amplitude is below the threshold (hereinafter referred to as "non-excess signals") according to the determination result of the determination unit 11. Specifically, the distribution unit 12 outputs the non-excess signal when the amplitude of the input signal is below the threshold to the output terminal 102, and outputs the excess signal when the amplitude of the input signal exceeds the threshold to the replacement unit 21, the first calculation unit 22, and the second calculation unit 24, respectively.

[0026] The replacement unit 21 performs a replacement process on the input excess signal, replacing the amplitude exceeding a threshold with a constant value. The constant value is, for example, the threshold used in the determination of the determination unit 11. The replacement process by the replacement unit 21 is expressed by equation (2) above. The replacement unit 21 then performs a replacement on the clipped signal y p2 (kT) is output to the first calculation unit 22. The first calculation unit 22 subtracts the clipping signal output from the replacement unit 21 from the excess signal output from the distribution unit 12, and outputs the resulting first calculation signal to the filter unit 23.

[0027] The filter unit 23 filters the first calculation signal input from the first calculation unit 22 using a band elimination filter (BEF), and outputs the resulting filtered signal to the second calculation unit 24. The second calculation unit 24 subtracts the filtered signal output from the filter unit 23 from the excess signal output from the distribution unit 12, and feeds back the resulting second calculation signal to the input of the determination unit 11.

[0028] The determination unit 11 determines whether the amplitude of the second calculation signal output from the second calculation unit 24 exceeds a preset threshold. However, if the second calculation signal is fed back to the determination unit 11, the PAPR may saturate, potentially causing the feedback operation to repeat indefinitely. To prevent this, the distribution unit 12 outputs the second calculation signal to the output terminal 102 if the number of feedback cycles from the second calculation unit 24 to the determination unit 11 exceeds a preset upper limit (for example, 50 times), even if the determination unit 11 determines that the amplitude of the second calculation signal exceeds the threshold.

[0029] Figure 2 is a flowchart showing the flow of PAPR suppression processing in Embodiment 1. First, the feedback count M is initialized to 0 (S1). Then, the determination unit 11 determines whether or not the amplitude of the input signal exceeds a preset threshold (S2). The signal input to the determination unit 11 is either the input signal input to the input terminal 101 or the second calculation signal output from the second calculation unit 24. If the amplitude of the signal input to the determination unit 11 is less than or equal to the threshold (S2: NO), the desired PAPR is met, and the distribution unit 12 outputs a non-exceeding signal to the output terminal 102 (S3).

[0030] If the amplitude of the signal input to the determination unit 11 exceeds a threshold (S2: YES), the distribution unit 12 determines whether the number of feedback cycles M is equal to or greater than a preset upper limit (S4). If the number of feedback cycles M is less than the upper limit (S4: NO), the distribution unit 12 outputs the excess signal to the replacement unit 21, the first calculation unit 22, and the second calculation unit 24, respectively.

[0031] Then, the replacement unit 21 performs a replacement process in which the amplitude exceeding a threshold for the excess signal is replaced with a constant value (S5). Subsequently, the first calculation unit 22 performs a first calculation process (S6). Figure 3 is a diagram illustrating the first calculation process by the first calculation unit 22 according to Embodiment 1. Figure 3(a) shows the excess signal x(kT) distributed by the distribution unit 12, and Figure 3(b) shows the replacement process in the replacement unit 21. In the first calculation process, the first calculation unit 22 replaces the clipped signal y from the excess signal x(kT) shown in Figure 3(a) with the clipped signal y replaced by the replacement unit 21. p2 Subtracting (kT), the result is the first calculated signal y shown in Figure 3(c). p4 (kT) is output. The subtraction operation in the first arithmetic unit 22 is expressed by equation (7).

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[0032] In the first calculation process, the clipped signal replaced by the replacement unit 21 is subtracted from the excess signal whose amplitude exceeds the threshold determined by the determination unit 11, thereby obtaining the component in the excess signal whose amplitude exceeds the threshold. The first calculation signal obtained by the first calculation process is output to the filter unit 23.

[0033] Returning to Figure 2, the filter unit 23 performs BEF filtering on the first calculation signal input from the first calculation unit 22 (S7). The BEF filtering in the filter unit 23 is expressed by the following equations (8), (9), and (10).

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[0034] In equation (8), y p5 (kT) is the filtered signal output by the filter unit 23, and y p4 (kT) is the first operation signal, * is the convolution operation, and h BEF (kT) is the time-domain filter coefficient. In equation (9), N is the number of samples, n is the sample number expressed as an integer, and H BEF (n / NT) is the filter coefficient in the frequency domain. In equation (10), f low is the lower limit bandwidth frequency of the excess signal (the input signal input to input terminal 101 or the second processed signal that has been fed back), and f high y is the upper limit bandwidth frequency of the excess signal (the input signal input to input terminal 101 or the second processed signal that has been fed back), and f is the frequency of the first processed signal. In equation (10), the characteristics of the BEF are set to match the desired frequency band. In equation (9), the filter coefficients of the BEF generated in equation (10) are converted into time-domain filter coefficients by inverse Fourier transform. In equation (8), the impulse response of the filter coefficients of the BEF generated in equation (9) and the first processed signal y are shown in the time domain. p4 (kT) is convolved. In the filter section 23, the first operation signal y p4 The frequency band of the excess signal is removed from (kT). The filtered signal, filtered by the filter unit 23, is output to the second calculation unit 24.

[0035] Next, the second arithmetic unit 24 performs the second arithmetic processing (S8). Figure 4 is a diagram illustrating the second arithmetic processing by the second arithmetic unit 24 according to Embodiment 1. Figure 4(a) shows the excess signal distributed by the distribution unit 12, and Figure 4(b) shows the filtering in the filter unit 23. In the second arithmetic processing, the second arithmetic unit 24 subtracts the filtered signal filtered by the filter unit 23 from the excess signal shown in Figure 4(a), and outputs the second arithmetic signal shown in Figure 4(c) as a result. The second arithmetic signal obtained by the second arithmetic processing is fed back to the determination unit 11.

[0036] In the second calculation process, the excess signal, which has been determined by the determination unit 11 to have an amplitude exceeding the threshold, is subtracted from the filtered signal by the filter unit 23, thereby removing the component that exceeds the threshold from the excess signal.

[0037] Returning to Figure 2, 1 is added to the feedback count M (S9), and the process returns to step S2. If the feedback count M is 1 or greater, the determination unit 11 determines in step S2 whether the amplitude of the second calculation signal input from the second calculation unit 24 exceeds a preset threshold. If the amplitude of the second calculation signal is less than or equal to the threshold (S2: NO), the desired PAPR is met, and the distribution unit 12 outputs the second calculation signal to the output terminal 102 (S3).

[0038] On the other hand, if the amplitude of the second calculation signal exceeds the threshold (S2:YES), the distribution unit 12 determines whether the number of feedback cycles M is equal to or greater than a preset upper limit (S4). If the number of feedback cycles M is less than the preset upper limit (S4:NO), the processing in steps S5 to S9 is repeated. On the other hand, if the number of feedback cycles M is equal to or greater than the upper limit (S4:YES), the distribution unit 12 outputs the second calculation signal to the output terminal 102 (S3).

[0039] As described above, in the information processing device 100 of Embodiment 1, the PC processing unit 2 performs filtering using BEF on the first calculation signal output by the first calculation unit 22 using the filter unit 23, and removes the frequency band component of the excess signal (the input signal input to the input terminal 101 or the second calculation signal that has been fed back), thereby suppressing the increase in EVM. Figure 5 is a diagram illustrating the effect of the information processing device 100 according to Embodiment 1 in the frequency domain. In Figure 5, the vertical axis of each waveform shows the power level [dB] (hereinafter referred to as "PL") in the frequency domain, and the horizontal axis shows the frequency [Hz].

[0040] Figure 5(a) is a diagram illustrating the input signal (OFDM signal) input to input terminal 101 in the frequency domain. Figure 5(b) is a diagram illustrating the first arithmetic signal output from the first arithmetic unit 22 in the frequency domain. As shown in Figure 5(b), the first arithmetic signal also has power in the frequency band FRo of the input signal. Therefore, if the first arithmetic signal is input directly to the second arithmetic unit 24, it is subtracted down to the frequency band of the input signal, and the EVM increases.

[0041] Therefore, by filtering the first calculated signal shown in Figure 5(b) using BEF in the filter unit 23, a filtered signal can be obtained by removing the frequency band component of the input signal from the first calculated signal shown in Figure 5(c). If the filter characteristics of the filter unit 23 are those of an ideal filter where the amplitude characteristic is 0 dB in the passband, i.e., outside the frequency band of the input signal, and -∞ dB in the stopband, i.e., the frequency band component of the input signal, then subtracting this from the output signal from the distribution unit 12 in the time domain will not increase the EVM of the subtracted signal at all.

[0042] Unlike an ideal filter, the output of an actual filter exhibits a gradual frequency response near the frequency to be restricted, as shown in the output signal of the filter section 23 in the frequency domain of Embodiment 1. Therefore, it is difficult to set the EVM of the subtracted signal to 0. For example, if the desired PAPR suppression amount is -8dB, the EVM in the second calculated signal shown in Figure 5(d) is 0.77%, not 0%.

[0043] Figure 6 is a diagram illustrating the operation of the information processing device according to the comparative example in the frequency domain. The information processing device of the comparative example does not include the filter unit 23 of the information processing device 100 of Embodiment 1. Figure 6(a) is a diagram illustrating the input signal (OFDM signal) input to the input terminal 101 in the frequency domain. Figure 6(b) is a diagram illustrating the first arithmetic signal output from the first arithmetic unit in the frequency domain. In the comparative example, the first arithmetic signal is directly input to the second arithmetic unit, and the first arithmetic signal is subtracted from the input signal. For example, if the desired PAPR suppression amount is -8dB, the EVM in the second arithmetic signal shown in Figure 6(c) becomes 1.91%, which is 1.15% higher than the EVM of the second arithmetic signal of Embodiment 1.

[0044] Figure 7 is a table showing the simulation results of the EVM for the comparative example and Embodiment 1 for a desired PAPR suppression amount, and Figure 8 is a graph of the simulation results in Figure 7. Figures 7 and 8 show the change in EVM when the desired PAPR suppression amount in the input signal is changed from 0 dB to -10 dB. As shown in Figure 8, it can be seen that in Embodiment 1, the increase in EVM with respect to the PAPR suppression amount is more gradual compared to the comparative example. Also, as shown in Figure 7, it can be seen that in Embodiment 1, the EVM when the PAPR suppression amount is -8 dB is improved by approximately 1.14% compared to the comparative example.

[0045] As described above, in the information processing device 100 of Embodiment 1, PC processing is performed by the PC processing unit 2, which includes a replacement unit 21, a first calculation unit 22, a filter unit 23, and a second calculation unit 24, on excess signals whose amplitude exceeds a threshold, thereby suppressing PAPR while suppressing the increase in EVM.

[0046] Embodiment 2. Embodiment 2 will now be described. In the information processing device 100 of Embodiment 1 described above, PAPR can be suppressed while suppressing the increase in EVM, but the PAPR of the signal actually output may be larger than the desired PAPR. This is because, in Embodiment 1, filtering is performed by the filter unit 23 in the PC processing, which limits the amount of PAPR that can be suppressed. In Embodiment 1, since filtering using BEF is performed on the first calculation signal output from the first calculation unit 22, the PAPR of the second calculation signal output from the second calculation unit 24 may be larger than the PAPR of the clipped signal output from the replacement unit 21.

[0047] As a countermeasure, the second calculation signal is fed back to the input of the determination unit 11, but even if the number of feedbacks is increased, the PAPR of the signal output from the second calculation unit 24 saturates at a constant value. When the PAPR saturates and the number of feedbacks reaches the upper limit, even if the amplitude of the second calculation signal exceeds the threshold, the distribution unit 12 outputs it to the output terminal 102 as being below the threshold. Therefore, the PAPR of the signal output to the output terminal 102 will not have the desired PAPR suppression amount suppressed. If the desired PAPR suppression amount is not suppressed, there is a risk of overloading the stage after the output terminal 102.

[0048] The information processing device 100A of Embodiment 2 solves the above problems. Figure 9 is a schematic diagram of the information processing device 100A according to Embodiment 2. The information processing device 100A of Embodiment 2 is a device that performs a first threshold exceedance determination process, PC processing, a second threshold exceedance determination process, and clipping processing on an input signal input to the input terminal 101, and outputs a signal with PAPR suppressed from the output terminal 102.

[0049] The information processing device 100A includes a computer equipped with a processor such as a CPU and memory, a dedicated processing circuit such as an ASIC or FPGA, or both. As shown in Figure 9, the information processing device 100A includes, as a functional unit, a first determination processing unit 1A that performs a first threshold exceedance determination process, a PC processing unit 2 that performs PC processing, a second determination processing unit 3 that performs a second threshold exceedance determination process, and a clipping processing unit 4 that performs clipping processing.

[0050] The first determination processing unit 1A has the same functions as the determination processing unit 1 of Embodiment 1 and comprises the determination unit 11 and distribution unit 12 of Embodiment 1. However, in Embodiment 2, the distribution unit 12 outputs the input signal or the second calculation signal to the determination unit 31 of the second determination processing unit 3 when the amplitude of the input signal is below a threshold or when the number of feedback cycles by PC processing is above an upper limit. The PC processing unit 2 has the same functions as Embodiment 1 and comprises a replacement unit 21, a first calculation unit 22, a filter unit 23, and a second calculation unit 24. The second determination processing unit 3 comprises a determination unit 31 and a distribution unit 32. The clipping processing unit 4 comprises a replacement unit 41. Each functional unit of the information processing device 100A is realized by reading and executing an information processing program stored in memory, or by a processing circuit corresponding to each functional unit.

[0051] The determination unit 31 of the second determination processing unit 3 determines whether the amplitude of the signal (input signal or second calculation signal) output from the distribution unit 12 of the first determination processing unit 1A exceeds a preset threshold. The distribution unit 32 of the second determination processing unit 3 distributes the output destinations of the excess signal (whose amplitude exceeds the threshold) and the non-excess signal (whose amplitude is below the threshold) according to the determination result of the determination unit 31. Specifically, the distribution unit 32 outputs the non-excess signal to the output terminal 102 and the excess signal to the replacement unit 41.

[0052] The replacement unit 41 of the clipping processing unit 4 performs clipping processing on the input excess signal, replacing the amplitude exceeding a threshold with a constant value. The constant value is, for example, the threshold used for determination by the determination unit 31. Figure 10 is a diagram illustrating the clipping processing by the replacement unit 41 according to Embodiment 2. The replacement unit 41 performs replacement processing on excess signals that have been determined by the determination unit 31 shown in Figure 10(a) to have an amplitude exceeding a threshold and have been distributed by the distribution unit 32, and outputs the clipped signal shown in Figure 10(b). The replacement processing by the replacement unit 41 is expressed by the following equation (11).

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[0053] In equation (11), A is a predetermined threshold, and y p5 (kT) is the second calculation signal input to the replacement unit 41 as an excess signal, and y p6 (kT) is the signal output by the replacement unit 41. The signal replaced by the replacement unit 41 is output to the output terminal 102. In Embodiment 2, clipping processing is added, so the output signal of the output terminal 102 has an increased EVM compared to the signal of the output terminal 102 in Embodiment 1. However, since clipping processing is performed on the second calculation signal which has already undergone PC processing, the amount of clipping in the replacement unit 41 is small, and as a result, the increase in EVM can be prevented more effectively than in the conventional technology.

[0054] Figure 11 is a flowchart showing the operation flow of the information processing device 100A according to Embodiment 2. The processing in steps S1, S2, and S4-S9 in Figure 11 is the same as in Embodiment 1. If the amplitude of the signal input to the determination unit 11 is less than or equal to a threshold (S2: NO), or if the number of feedback counts M is greater than or equal to an upper limit (S4: YES), the distribution unit 12 outputs the input signal or the second calculation signal to the determination unit 31, and the determination unit 31 determines whether or not the amplitude of the input signal exceeds a preset threshold (S21).

[0055] If the amplitude of the signal input to the determination unit 31 is less than or equal to the threshold (S21: NO), the input signal is considered to satisfy the desired PAPR and is output to the output terminal 102 by the distribution unit 32 (S23). On the other hand, if the amplitude of the signal input to the determination unit 31 exceeds the threshold (S21: YES), the distribution unit 32 outputs the signal to the replacement unit 41. The replacement unit 41 then performs a clipping process to replace the amplitude exceeding the threshold in the input signal with a constant value (S22). The signal replaced by the replacement unit 41 is then output to the output terminal 102 (S23).

[0056] As described above, in the information processing device 100A of Embodiment 2, by further clipping the output signal of the information processing device 100 in Embodiment 1, it is possible to prevent the PAPR of the actual output signal from becoming higher than the desired PAPR, that is, to prevent PAPR degradation, while suppressing the decrease in EVM compared to the conventional technology.

[0057] Figure 12 is a table showing the simulation results of the actual PAPR suppression amounts in Embodiment 1 and Embodiment 2 for a desired PAPR suppression amount, and Figure 13 is a graph of the simulation results in Figure 12. Figures 12 and 13 show the actual PAPR suppression amounts when the desired PAPR suppression amount is set to 0 dB to -10 dB. The difference between the desired PAPR suppression amount and the actual PAPR suppression amount is defined as the PAPR degradation amount, and the degradation amounts in Embodiment 1 and Embodiment 2 are described below.

[0058] As shown in Figures 12 and 13, in Embodiment 1, the PAPR degradation begins to increase when the desired PAPR suppression amount is near -7 dB, and the PAPR degradation when the desired PAPR suppression amount is set to -8 dB is approximately 2.55 dB. In contrast, in Embodiment 2, the PAPR degradation can be kept within 0.3 dB in the range of 0 dB to -10 dB for the desired PAPR suppression amount.

[0059] Figure 14 is a table showing the simulation results of the EVM for the comparative example, Embodiment 1, and Embodiment 2 for a desired PAPR suppression amount, and Figure 15 is a graph of the simulation results in Figure 14. Figures 14 and 15 show the change in EVM when the desired PAPR suppression amount is changed from 0 dB to -10 dB. As shown in Figures 14 and 15, when the desired PAPR suppression amount is around -7 dB to -8 dB, the EVM of Embodiment 2 begins to increase, and when the desired PAPR suppression amount is -8 dB, the EVM of the output signal of Embodiment 2 is 0.18% higher than that of Embodiment 1. However, it is lower than the EVM of the comparative example, indicating that the suppression capability of the EVM is improved compared to the comparative example. Furthermore, the difference in EVM between the output signals of Embodiment 1 and Embodiment 2 can be kept within 1.4%.

[0060] In other words, in the information processing device 100A of Embodiment 2, by newly performing a second threshold exceedance determination process and a clipping process on the output signal of Embodiment 1, it is possible to reduce the deterioration of the PAPR suppression amount that occurred in Embodiment 1, while suppressing the increase in EVM compared to the conventional technology.

[0061] The above describes embodiments of the present invention, but the present invention is not limited to the configuration of the above embodiments, and various modifications or combinations are possible within the scope of its technical idea. For example, in Embodiment 1 above, the subtraction process of equation (7) is performed to obtain the first operation signal y p4 We derived (kT), but the first operation signal y p4 (kT) can be generated in any way as long as it satisfies the following equation (12).

number

[0062] Furthermore, in the above embodiment, filtering is performed using a BEF in the filter section 23, but any type of filter that cuts out components outside the usable frequency band may be used.

[0063] Furthermore, filtering may be performed in the filter unit 23 using either analog or digital methods. Naturally, a program is provided to cause the information processing device 100 to function as such a filter.

[0064] Furthermore, this disclosure naturally includes a program for causing the processor of the information processing device to execute the processing in each processing unit described in each of the above embodiments, and a storage medium storing the program. [Explanation of symbols]

[0065] 1 Judgment processing unit, 1A First judgment processing unit, 2 PC processing unit, 3 Second judgment processing unit, 4 Clipping processing unit, 11, 31 Judgment unit, 12, 32 Distribution unit, 21, 41 Replacement unit, 22 First calculation unit, 23 Filter unit, 24 Second calculation unit, 51 Input terminal, 52 Output terminal, 100, 100A, 500 Information processing unit, 101 Input terminal, 102 Output terminal, 501 Judgment unit, 502 Distribution unit, 503 Replacement unit, 504 BPF.

Claims

1. An information processing device that suppresses the peak power to average power ratio of a signal, A determination processing unit that determines whether the amplitude of the input signal exceeds a preset threshold, The system includes a PC processing unit that performs peak canceling processing on excess signals whose amplitude is determined to exceed the threshold, thereby reducing the amplitude exceeding the threshold. The PC processing unit is an information processing device that includes a filter unit that performs filtering to remove the frequency band component of the excess signal from the input signal.

2. The aforementioned PC processing unit is A replacement unit performs a replacement process on the aforementioned excess signal, replacing the amplitude exceeding the threshold with a constant value, and outputs it as a clipped signal. A first calculation unit subtracts the clipping signal from the excess signal and outputs it as a first calculation signal, The filter unit performs the filtering on the first calculation signal and outputs it as a filtered signal, The information processing apparatus according to claim 1, further comprising: a second calculation unit that subtracts the filter signal from the excess signal and feeds back the result as a second calculation signal to the determination processing unit.

3. The determination processing unit includes a distribution unit that distributes the output destination of the excess signal to the output destination of the non-excess signal whose amplitude is determined to be below the threshold, The information processing apparatus according to claim 2, wherein the distribution unit distributes the second calculation signal to the output destination of the non-exceeding signal even if the amplitude of the second calculation signal exceeds the threshold when the number of feedbacks by the second calculation unit exceeds a preset upper limit.

4. The aforementioned determination processing unit is the first determination processing unit, A second determination processing unit that determines whether the amplitude of the second calculation signal output from the first determination processing unit exceeds the threshold, The information processing apparatus according to claim 3, further comprising: a clipping processing unit that, when the second determination processing unit determines that the amplitude of the second calculation signal exceeds the threshold, performs a clipping processing on the second calculation signal, replacing the amplitude exceeding the threshold with a constant value.

5. The information processing apparatus according to any one of claims 1 to 4, wherein the filtering unit performs the filtering using a bandwidth limiting filter.

6. An information processing method for suppressing the peak power to average power ratio of a signal, A determination process step that determines whether the amplitude of the input signal exceeds a preset threshold, The system includes a PC processing step that performs peak canceling processing on excess signals whose amplitude is determined to exceed the threshold, thereby reducing the amplitude exceeding the threshold. The PC processing step is an information processing method that includes a filtering step to remove the frequency band component of the excess signal from the input signal.

7. An information processing program that suppresses the peak power to average power ratio of a signal, A determination process step that determines whether the amplitude of the input signal exceeds a preset threshold, The system involves a PC processing step in which a computer performs a peak canceling process to reduce the amplitude of an excess signal that is determined to have an amplitude exceeding the threshold, thereby reducing the amplitude exceeding the threshold. The PC processing step is an information processing program that includes a filtering step to remove the frequency band component of the excess signal from the input signal.

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