JP2017085241A - Peak reduction circuit, OFDM signal transmission device and chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress deterioration of EVM in a TR method for reducing a peak of an OFDM signal by setting dummy data to a subcarrier to which data are not allocated.SOLUTION: Time shift means 31 of a peak reduction signal generation part 22 shifts a time (k) of a dummy signal δ(k) for a time of a peak position P and generates a dummy signal δ'(k). Phase adjusting means 32 generates a cancel signal d(k) by adjusting a phase of the dummy signal δ'(k) in such a manner that a peak value s(P) becomes equal to a cancel signal d(P). A scaling part 23 adjusts a level of a peak reduction signal D(n) on which FFT of the cancel signal d(k) has been performed. An AC embedding part 25 embeds a peak reduction signal D(n)/C of which the level has been adjusted, in a subcarrier of an AC signal to which data are not allocated in a signal S(n) of a frequency domain. Thus, a signal s'(k) of a time domain of which the peak has been reduced is generated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a peak reduction circuit, an OFDM signal transmission apparatus, and a chip for reducing a peak of a modulation signal in multicarrier modulation.

  FIG. 15 is a block diagram illustrating a configuration example of a conventional OFDM (Orthogonal Frequency Division Multiplexing) signal transmission apparatus. The OFDM signal transmission apparatus 100 includes a data mapping unit 10, a subcarrier arrangement unit 11, an IFFT (Inverse Fast Fourier Transform) unit 12, and a GI (Guard Interval) adding unit 13. The OFDM signal transmission apparatus 100 performs OFDM modulation on data to be transmitted to generate an OFDM signal, and transmits the OFDM signal.

  The data mapping unit 10 receives data to be transmitted, performs carrier modulation on the data, maps the data to the IQ axis, and generates a modulated signal. Then, the data mapping unit 10 outputs the modulated signal mapped to the IQ axis to the subcarrier arrangement unit 11.

  The subcarrier arrangement unit 11 receives the modulation signal from the data mapping unit 10, arranges the modulation signal on the subcarrier in the frequency domain, and generates the frequency domain signal S (n) (frequency domain OFDM signal S (n)). Generate. Here, n indicates a subcarrier number in the frequency domain. Then, the subcarrier arrangement unit 11 outputs the frequency domain signal S (n) to the IFFT unit 12.

  FIG. 16 is a diagram for explaining a signal S (n) in the frequency domain. The horizontal axis indicates the subcarrier number n on the frequency axis, and the vertical axis indicates the frequency domain signal S (n). The frequency domain signal S (n) is complex number data mapped on the IQ axis, and it is assumed that one symbol length in the frequency domain consists of subcarriers of N samples (N points). This frequency region includes a region in the band and regions outside the band located on both sides of the region in the band. In the region within the band, modulation signals that are carrier-modulated transmission target data, control information, and the like are arranged on M subcarriers with subcarrier numbers n = 0 to M−1.

  In the example of FIG. 16, a modulated signal that is carrier-modulated transmission target data is transmitted to subcarriers of subcarrier numbers n = 0, 1, 3, 5,..., M,. Be placed. Also, control information other than data to be transmitted (for example, TMCC (Transmission and Multiplexing Configuration and Control) signal), known data for channel estimation (for example, SP (Scattered) Pilot: Scattered pilot) signal), pilot data such as auxiliary data (for example, AC (Auxiliary Channel) signal) that can be arbitrarily set by the user are arranged.

  That is, the subcarrier arrangement unit 11 arranges a modulation signal, which is carrier-modulated transmission target data, on a predetermined subcarrier, and arranges preset control information or the like on another predetermined subcarrier, An area signal S (n) is generated.

  Returning to FIG. 15, IFFT unit 12 receives frequency domain signal S (n) from subcarrier arrangement unit 11, performs IFFT on frequency domain signal S (n), and performs time domain signal s (k). (Time domain OFDM signal s (k)) is generated. Here, k indicates time. Then, IFFT unit 12 outputs time domain signal s (k) to GI adding unit 13.

  The GI adding unit 13 receives the time-domain signal s (k) from the IFFT unit 12, and at the head of the signal s (k) corresponding to the effective symbol period, a predetermined signal s (k) corresponding to the effective symbol period. GI is added by copying the part after the. Then, the signal to which the GI is added by the GI adding unit 13 is subjected to frequency conversion and the like, and then transmitted from the OFDM signal transmitting apparatus 100 as an OFDM signal.

  In this way, the OFDM signal transmitting apparatus 100 performs processing such as data mapping, subcarrier arrangement, IFFT, and GI addition on the transmission target data, and the transmission target data is transmitted as an OFDM signal.

By the way, in the IFFT section 12 of the OFDM signal transmitting apparatus 100 shown in FIG. 15, the frequency domain signal S (n) is converted into the time domain signal s (k) by IFFT. Assuming that the frequency domain signal S (n) is arranged in the subcarrier number n shown in FIG. 16, the IFFT unit 12 performs the frequency domain signal S in discrete time IFFT according to the following equation. A time domain signal s (k) is generated from (n).

  From the equation (1), when the phase of the multiplication result of the frequency domain signal S (n) and the exponential function with exp as the base coincides at every time k, the time domain signal s (k) at a certain time. It can be seen that the instantaneous value of can be a large peak.

  FIG. 17 is a diagram illustrating a waveform example of an OFDM signal. The horizontal axis indicates time (sample), and the vertical axis indicates the amplitude of the OFDM signal. The waveform of this OFDM signal is a waveform example of the signal s (k) in the time domain generated by the IFFT unit 12 of the OFDM signal transmitting apparatus 100 shown in FIG. Is 1.

  From FIG. 17, it can be seen that the OFDM signal has a peak that is much larger than its average value of 1 at a certain time. As described above, the peak appears in the OFDM signal because the phase of the signal S (n) in the frequency domain and the exponential function exp match in the equation (1) in which IFFT processing is performed by the IFFT unit 12. is there. Therefore, the fact that the OFDM signal has an instantaneous peak is a phenomenon that inevitably occurs.

  When the peak of such an OFDM signal becomes high, the OFDM signal amplified by the amplifier (the amplifier not shown provided in the subsequent stage of the IFFT unit 12 and the GI adding unit 13 in FIG. 15) has distortion. And degradation of the transmission signal from the OFDM signal transmission apparatus 100 becomes large, and as a result, the transmission characteristics are adversely affected.

  Conventionally, various methods for reducing the peak of an OFDM signal have been proposed. For example, a technique is known in which an OFDM signal is distorted to repeat the process of reducing the peak a plurality of times (see, for example, Patent Document 1). In this method, a peak exceeding a predetermined threshold is reduced among OFDM signals in the time domain, and a series of FFT (Fast Fourier Transform) and IFFT processes are repeated a plurality of times.

JP 2013-162282 A

  In general, representative methods for reducing the peak of an OFDM signal include CAF method (Clipping and Filtering method), TR method (Tone Reservation method) and PTS method (Partial Transmit Sequence). : Partial sequence transmission method).

  The CAF method is a method of distorting an OFDM signal and reducing the peak of the OFDM signal by combining clipping processing and filtering processing.

  According to this CAF method, peak reduction can be realized with a relatively small calculation cost and circuit scale. However, since it is a technique for distorting an OFDM signal, EVM (Error Vector Magnitude: modulation accuracy) is deteriorated. On the other hand, the technique disclosed in Patent Document 1 described above suppresses the degradation of the EVM by repeatedly performing a process of distorting the OFDM signal to reduce its peak and reducing the amount of peak reduction per time. However, the degradation of EVM cannot be completely removed.

  The TR method is a method of setting dummy data for peak reduction in subcarriers to which no data is assigned in a frequency domain OFDM signal. The TR method mainly includes processing for detecting a peak and processing for generating dummy data. There is also a method of repeatedly performing a peak detection process and a dummy data generation process.

  According to the TR method, since the data is not manipulated, the degradation of the EVM can be suppressed. However, the process of generating dummy data requires a complicated complex operation, which increases the calculation cost. In particular, in the method of repeatedly performing the peak detection process and the dummy data generation process, the calculation cost is further increased.

  The PTS method is a technique for reducing OFDM signal peaks by subjecting transmission target data to phase rotation and OFDM modulation. Specifically, a plurality of phase rotation patterns are prepared, OFDM signals are generated for all patterns, and the OFDM signal having the lowest peak is selected and transmitted from among the generated OFDM signals.

  According to this PTS method, since it is necessary to generate a plurality of OFDM signals in order to transmit one system of OFDM signals, the calculation cost becomes very high. Further, since the phase rotation applied to the data needs to be restored on the reception side, it is necessary to transmit the phase rotation pattern from the transmission side to the reception side by some method. For this reason, when the data phase can be completely restored on the receiving side, the EVM is not degraded as in the TR method.

  In the present invention, attention is paid to the above-described TR method. As described above, the TR method generates dummy data for peak reduction, and sets the dummy data in subcarriers to which no data is assigned, thereby suppressing EVM degradation. In this case, in the TR method, it has been desired to generate dummy data capable of effectively suppressing the degradation of EVM in the process of generating peak-reducing dummy data.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to set dummy data on subcarriers to which no data is assigned, and in the TR method for reducing the peak of the OFDM signal, the EVM is used. An object of the present invention is to provide a peak reduction circuit, an OFDM signal transmission device, and a chip that can generate dummy data that effectively suppress degradation.

  In order to solve the above problem, the peak reduction circuit according to claim 1 sets predetermined dummy data to a subcarrier to which no data is assigned in a frequency domain OFDM signal, and reduces a peak of the time domain OFDM signal. In the peak reduction circuit, a peak detection unit that detects a time position at which the amplitude within one symbol in the OFDM signal in the time domain is maximum as a peak position, and detects the OFDM signal in the time domain at the peak position as a peak value And a signal for reducing the peak value detected by the peak detection unit, and a peak reduction signal in a frequency region having a predetermined peak value at the same position as the peak position detected by the peak detection unit A peak reduction signal generation unit that generates the peak reduction signal generation unit and the peak reduction signal generation unit A scaling unit that scales by dividing a peak reduction signal in the wave number domain by a predetermined scale value, and a part of the scaled peak reduction signal scaled by the scaling unit is the predetermined dummy data, and the dummy data Is embedded in a subcarrier to which no data is assigned in the frequency domain OFDM signal, and the frequency domain OFDM signal in which the dummy data is embedded by the embedding unit is subjected to IFFT (Inverse Fast Fourier Transform), An IFFT unit that generates an OFDM signal in a time domain in which the peak is reduced.

  The peak reduction circuit according to claim 2 is the peak reduction circuit according to claim 1, wherein the peak reduction signal generation unit applies IFFT to a dummy data string in a frequency domain in which predetermined data is arranged on a frequency axis. IFFT means for generating a time domain dummy signal, and shifting the time of the time domain dummy signal generated by the IFFT means by the time of the peak position detected by the peak detection unit A time shift means for generating a time domain dummy signal; a phase adjustment means for adjusting a phase of the new time domain dummy signal generated by the time shift means to generate a time domain cancellation signal; and FFT means for applying FFT to the time domain cancellation signal generated by the adjusting means to generate a peak reduction signal in the frequency domain; And the phase adjusting means makes the phase of the peak value detected by the peak detector the same as the phase of the value of the cancellation signal at the same position as the peak position detected by the peak detector. As described above, the time domain cancellation signal is generated by adjusting the phase of the new time domain dummy signal.

  The peak reduction circuit according to claim 3 is the peak reduction circuit according to claim 1, wherein the peak reduction signal generator rotates between 0 and 2π when one symbol consists of a predetermined number of points. Using a memory storing a table containing phase data for each point and using phase data of the table stored in the memory, a phase of a dummy data string in a frequency domain in which predetermined data is arranged on the frequency axis Is adjusted according to the peak position and the peak value detected by the peak detector, and generates a peak reduction signal in the frequency domain, and the signal generator includes the peak position Based on the above, the read position when reading the phase data of the table stored in the memory is specified, from the table stored in the memory, The phase data of the protruding position is sequentially read, the phase of the dummy data string in the frequency domain is adjusted by the phase of the read phase data, and the time shift stage for generating the time shift signal in the frequency domain, and the peak value A phase identification stage for identifying a phase based on the phase identification stage, and adjusting a phase of the time shift signal in the frequency domain generated by the time shift stage by the phase identified by the phase identification stage to reduce the peak in the frequency domain And a phase adjustment stage for generating a signal.

  The peak reduction circuit according to claim 4 is the peak reduction circuit according to claim 1, wherein the peak reduction signal generator rotates between 0 and 2π when one symbol consists of a predetermined number of points. Using a memory storing a table containing phase data for each point and using phase data of the table stored in the memory, a phase of a dummy data string in a frequency domain in which predetermined data is arranged on the frequency axis Is adjusted according to the peak position and the peak value detected by the peak detection unit, and a signal generation means for generating a peak reduction signal in the frequency domain, and the signal generation means includes the peak value A phase specifying stage for specifying the phase based on the reading position, and a reading position when reading the phase data of the table stored in the memory based on the peak position Identifying, shifting the readout position based on the phase identified by the phase identification stage, sequentially reading out phase data at the readout position after the shift from the phase conversion table stored in the memory, and It has a time shift and phase adjustment stage for adjusting the phase of the dummy data string in the region by the phase of the read phase data and generating a peak reduction signal in the frequency region.

  Furthermore, the OFDM signal transmission apparatus according to claim 5 maps the data to be transmitted and arranges the data on the frequency domain subcarrier, performs IFFT (Inverse Fast Fourier Transform) on the frequency domain signal, and generates the time domain OFDM signal. In the OFDM signal transmitting apparatus that generates and transmits the OFDM signal, the data to be transmitted is subjected to carrier modulation and mapped to the IQ axis, and a data mapping unit that generates a modulated signal and the data mapping unit The modulated signal is arranged on a subcarrier in the frequency domain, a subcarrier arrangement unit that generates a signal in the frequency domain, and the frequency domain signal generated by the subcarrier arrangement unit is subjected to IFFT, and an OFDM signal in the time domain IFFT unit for generating data and predetermined dummy data are generated by the subcarrier arrangement unit A signal whose peak is reduced from the time domain OFDM signal generated by the IFFT unit is set as a new time domain OFDM signal. A peak reduction processing unit to be generated, and a GI addition unit for adding a GI (guard interval) to the new time domain OFDM signal generated by the peak reduction processing unit, the peak reduction processing unit, A peak detection unit that detects a time position where the amplitude in one symbol in the time-domain OFDM signal generated by the IFFT unit is maximum as a peak position, and detects the signal at the peak position as a peak value; A signal for reducing the peak value detected by the peak detector, the peak value A peak reduction signal generation unit that generates a peak reduction signal of a frequency region having a predetermined peak value at the same position as the peak position detected by the detection unit, and a frequency reduction region of the frequency region generated by the peak reduction signal generation unit A scaling unit that scales by dividing the peak reduction signal by a predetermined scale value, a part of the peak reduction signal after scaling scaled by the scaling unit is the predetermined dummy data, and the dummy data is An embedding unit embedded in a subcarrier to which no data is assigned in a frequency domain signal, and IFFT is applied to the frequency domain signal in which the dummy data is embedded by the embedding unit, and a new time domain in which the peak is reduced And an IFFT unit for generating an OFDM signal. It is a sign.

  Furthermore, the chip of claim 6 maps the data to be transmitted and arranges it on frequency domain subcarriers, performs IFFT (Inverse Fast Fourier Transform) on the frequency domain signal, and generates an OFDM signal in the time domain, In a chip mounted on an OFDM signal transmission apparatus that transmits the OFDM signal, the OFDM signal transmission apparatus performs data carrier modulation on the transmission target data and maps it to an IQ axis, and generates a modulation signal; The modulation signal generated by the data mapping unit is arranged on a subcarrier in a frequency domain, a subcarrier arrangement unit that generates a frequency domain signal, and the frequency domain signal generated by the subcarrier arrangement unit An IFFT unit that performs IFFT and generates an OFDM signal in a time domain, and predetermined dummy data, A signal having a peak reduced from the time domain OFDM signal generated by the IFFT unit is set to a subcarrier to which data in the frequency domain signal generated by the subcarrier allocation unit is not allocated. A peak reduction processing unit that generates a time domain OFDM signal, and a GI addition unit that adds a GI (guard interval) to the new time domain OFDM signal generated by the peak reduction processing unit, The peak reduction processing unit detects the time position where the amplitude in one symbol in the time-domain OFDM signal generated by the IFFT unit is maximized as a peak position, and detects the signal at the peak position as a peak value. Peak detection unit that reduces the peak value detected by the peak detection unit A peak reduction signal generator for generating a peak reduction signal in a frequency region having a predetermined peak value at the same position as the peak position detected by the peak detector, and the peak reduction signal A scaling unit that scales by dividing the frequency domain peak reduction signal generated by the generation unit by a predetermined scale value; and a part of the scaled peak reduction signal that is scaled by the scaling unit The dummy data is embedded in a subcarrier to which no data in the frequency domain signal is assigned, and the frequency domain signal in which the dummy data is embedded by the embedding unit is subjected to IFFT, Generate a new time-domain OFDM signal with reduced peaks The chip includes at least the peak reduction signal generation unit.

  As described above, according to the present invention, dummy data is set to subcarriers to which no data is allocated, and dummy data that effectively suppresses degradation of EVM is generated in the TR method for reducing the peak of an OFDM signal. It becomes possible.

It is a block diagram which shows the structural example of the OFDM signal transmitter by embodiment of this invention. It is a block diagram which shows the structural example of a peak reduction process part. It is a figure explaining the outline | summary of the process by a peak reduction signal production | generation part. FIG. 3 is a block diagram illustrating a configuration example of a peak reduction signal generation unit according to the first embodiment. 6 is a flowchart illustrating a processing example of a peak reduction signal generation unit according to the first embodiment. FIG. 6 is a diagram illustrating a processing example of a peak reduction signal generation unit according to the first embodiment. FIG. 10 is a block diagram illustrating a configuration example of a peak reduction signal generation unit according to the second embodiment. In Example 2, it is a figure explaining the data stored in the memory. It is a block diagram which shows the structural example of the peak reduction signal production | generation part of Example 2-1. It is a flowchart which shows the process example of the peak reduction signal production | generation part of Example 2-1. (1) is a figure which shows the example of the phase data of the peak position P = 2. (2) is a diagram illustrating an example of phase data at a peak position P = 3. It is a block diagram which shows the structural example of the peak reduction signal production | generation part of Example 2-2. It is a flowchart which shows the process example of the peak reduction signal production | generation part of Example 2-2. (1) is a diagram showing phase data when the peak position P = 1. (2) is a diagram showing phase data when the peak position P = 1 and the phase θ are adjusted. (3) is a diagram supplementing the explanation of (2) when the peak position P = 1 and the phase θ are adjusted. It is a block diagram which shows the structural example of the conventional OFDM signal transmitter. It is a figure explaining signal S (n) of a frequency domain. It is a figure which shows the example of a waveform of an OFDM signal.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
[OFDM signal transmitter]
First, an OFDM signal transmission apparatus according to an embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating a configuration example of an OFDM signal transmission apparatus according to an embodiment of the present invention. This OFDM signal transmission device 1 is a device that reduces the peak of an OFDM signal using the TR method, and includes a data mapping unit 10, a subcarrier arrangement unit 11, an IFFT unit 12, a peak reduction processing unit (peak reduction circuit) 20, and A GI adding unit 13 is provided.

  The OFDM signal transmission apparatus 1 generates dummy data, and sets the dummy data to a predetermined subcarrier to which no data is assigned in the frequency domain OFDM signal, thereby reducing the peak of the time domain OFDM signal. .

  Comparing the OFDM signal transmission apparatus 1 shown in FIG. 1 with the conventional OFDM signal transmission apparatus 100 shown in FIG. 15, both OFDM signal transmission apparatuses 1 and 100 include a data mapping unit 10, a subcarrier arrangement unit 11, an IFFT. It is the same in that the unit 12 and the GI adding unit 13 are provided. On the other hand, the OFDM signal transmission apparatus 1 is different from the OFDM signal transmission apparatus 100 in that it includes a peak reduction processing unit 20. In FIG. 1, the same reference numerals as those in FIG.

  The subcarrier arrangement unit 11 outputs the frequency domain signal S (n) in which the modulation signal is arranged on a predetermined subcarrier to the IFFT unit 12 and the peak reduction processing unit 20.

  The peak reduction processing unit 20 receives the time domain signal s (k) from the IFFT unit 12, and also receives the frequency domain signal S (n) from the subcarrier arrangement unit 11, and the time domain signal s (k). To detect a peak position P and a peak value s (P). The time domain signal s (k) has a peak at time k = P.

  The peak reduction processing unit 20 determines the peak value based on the peak position P, the peak value s (P), and the dummy data string Δ (n) that can be converted into a dummy signal δ (k) having a peak at k = 0. A signal for canceling s (P), and a peak reduction signal D (n) that can be converted into a cancellation signal d (k) having a predetermined peak value at the same position as the peak position P is generated. Details of the method of generating the frequency domain peak reduction signal D (n) will be described later.

  The peak reduction processing unit 20 embeds a part of the scaled peak reduction signal D (n) / C in a predetermined subcarrier to which no data is assigned in the frequency domain signal S (n), and performs IFFT. Thus, a time-domain signal s ′ (k) with a reduced peak is generated. Then, the peak reduction processing unit 20 outputs the signal s ′ (k) in the time domain in which the peak is reduced to the GI adding unit 13.

  The GI adding unit 13 receives the time-domain signal s ′ (k) whose peak has been reduced from the peak reduction processing unit 20 and adds the GI to the time-domain signal s ′ (k). The signal to which the GI is added is subjected to frequency conversion and the like, and then transmitted from the OFDM signal transmitting apparatus 1 as an OFDM signal.

[Peak reduction processing unit 20]
Next, the peak reduction processing unit 20 shown in FIG. 1 will be described in detail. FIG. 2 is a block diagram illustrating a configuration example of the peak reduction processing unit 20. The peak reduction processing unit 20 includes a peak detection unit 21, a peak reduction signal generation unit 22, a scaling unit 23, a delay correction unit 24, an AC (Auxiliary Channel) embedding unit 25, and an IFFT unit 26.

  The peak detection unit 21 receives the time-domain signal s (k) from the IFFT unit 12 and sets the time position k = P at which the amplitude within one symbol is maximum to the peak position with respect to the time-domain signal s (k). P is detected, and the signal s (P) at the time position P is detected as the peak value s (P). Then, the peak detector 21 outputs the peak position P and the peak value s (P) to the peak reduction signal generator 22. Various algorithms for peak detection have been studied. Since the detection processing of the peak position P and the peak value s (P) by the peak detection unit 21 is known, detailed description is omitted here.

  The peak reduction signal generation unit 22 inputs the peak position P and the peak value s (P) from the peak detection unit 21, and based on the peak position P and the peak value s (P), a preset dummy data string Δ ( n), a frequency domain signal D (n) that can be converted into a cancellation signal d (k) for canceling the peak value s (P) is generated. Then, the peak reduction signal generation unit 22 outputs the generated frequency domain signal D (n) to the scaling unit 23 as the peak reduction signal D (n).

  FIG. 3 is a diagram for explaining the outline of processing by the peak reduction signal generation unit 22. As shown in FIG. 3, a time domain cancellation signal d (k) for canceling the peak value s (P) is assumed. The cancellation signal d (k) is a signal having a peak value d (P) at time k = P, and other time position signals having a predetermined value close to 0.

  By adding the time domain signal s (k) having the peak value s (P) and the cancellation signal d (k) having the peak value d (P) (s (k) + d (k), In this case, the peak value d (P) can be reduced. That is, by using the cancellation signal d (k), the peak value d (P) can be reduced from the signal s (k) in the time domain, and the signal s ′ (k) in which the peak value s (P) is reduced. (See the arrow point α in the signal s ′ (k) in FIG. 3).

  Further, the peak reduction signal D (n) is generated by performing FFT on the cancellation signal d (k). For example, the peak reduction signal generator 22 generates a peak reduction signal D (n), and a cancellation signal d (() for canceling the peak value s (P) from a preset dummy data sequence Δ (n). k) is generated, and the cancellation signal d (k) is subjected to FFT to generate a peak reduction signal D (n). Here, the dummy data sequence Δ (n) is, for example, a data sequence in which “1” is appropriately arranged on the frequency axis, and complex data may be arranged instead of “1”.

  The frequency domain peak reduction signal D (n) generated by the peak reduction signal generator 22 is as shown in the lower part of FIG. The horizontal axis indicates the subcarrier number n on the frequency axis, and the vertical axis indicates the frequency domain peak reduction signal D (n). The peak reduction signal D (n) is composed of subcarriers of N samples (N points) each having a symbol length in the frequency domain, and M subcarriers with subcarrier numbers n = 0 to M−1 are in the band. is there. As shown in the lower part of FIG. 3, the subcarriers with subcarrier numbers n = 0,..., M−1 are based on, for example, a dummy data string Δ (n) in which “1” is arranged on the frequency axis. Data, dummy data for canceling the peak value s (P) is arranged.

  In the example of FIG. 3, the peak reduction signal D (n) is an OFDM signal in which out-of-band is set within N samples of one symbol length in the carrier arrangement in the frequency domain after FFT. It may be an OFDM signal with all long N samples as subcarriers.

  Returning to FIG. 2, the scaling unit 23 receives the peak reduction signal D (n) from the peak reduction signal generation unit 22, divides the peak reduction signal D (n) by a preset scale value C, and obtains a division result. The scaled peak reduction signal D (n) / C is output to the AC embedding unit 25.

  Thereby, the level of the peak reduction signal D (n) is adjusted, and the magnitude of the cancellation signal d (P) at the peak position P changes. That is, the amount of reduction of the peak value s (P) at the peak position P in the time-domain signal s (k) can be adjusted according to the scale value C.

  The delay correction unit 24 receives the frequency domain signal S (n) from the subcarrier arrangement unit 11 and outputs the frequency domain signal S (n) to the peak detection unit 21, the peak reduction signal generation unit 22, and the scaling unit 23. Delay by processing time. Then, the delay correction unit 24 outputs the delayed frequency domain signal S (n) to the AC embedding unit 25.

  Accordingly, the timing is matched between the delayed frequency domain signal S (n) output from the delay correcting unit 24 and the post-scaling peak reduction signal D (n) / C output from the scaling unit 23. The AC embedding unit 25 can receive the synchronized frequency domain signal S (n) and the peak reduction signal D (n) / C.

  The AC embedding unit 25 receives the frequency domain peak reduction signal D (n) / C from the scaling unit 23 and receives the delayed frequency domain signal S (n) from the delay correction unit 24. Then, the AC embedding unit 25 positions the same subcarrier as the AC signal in the peak reduction signal D (n) / C in the subcarrier of the AC signal to which no data is allocated among the subcarriers of the signal S (n). Are embedded to generate a frequency domain signal S ′ (n). The AC embedding unit 25 outputs the frequency domain signal S ′ (n) to the IFFT unit 26.

  Thereby, the dummy data of the peak reduction signal D (n) / C is embedded only in the subcarriers to which no data is allocated among the subcarriers of the signal S (n). In this case, the embedded dummy data does not completely correspond to the cancellation signal d (k) reproducing the dummy data of the subcarriers of all frequency components (dummy data of the peak reduction signal D (n) / C). Absent. However, by synthesizing a signal using a part of the frequency components of the cancellation signal d (k), a signal that is somewhat similar can be reproduced, so that it is embedded in a subcarrier of a part of the frequency component in the signal S (n). Even with dummy data, a certain effect can be expected as a signal for reducing the peak.

  The IFFT unit 26 receives the frequency domain signal S ′ (n) from the AC embedding unit 25, performs IFFT on the frequency domain signal S ′ (n), and generates a time domain signal s ′ (k). Then, IFFT unit 26 outputs time domain signal s ′ (k) to GI adding unit 13.

  In this way, the peak reduction processing unit 20 cancels the peak value s (P) based on the peak position P and peak value s (P) and the preset dummy data string Δ (n). A peak reduction signal D (n) that can be converted into d (k) is generated, and a part of the scaled peak reduction signal D (n) / C is assigned data among the frequency domain signal S (n). Embedded in the subcarrier of the AC signal that is not, a frequency domain signal S ′ (n) is generated and subjected to IFFT. As a result, the phase of the multiplication result of the signal S ′ (n) instead of the signal S (n) in the frequency domain and the exponential function exp at each time k in the equation (1) representing the IFFT processing in the IFFT unit 26. Therefore, the peak of instantaneous values in the signal s ′ (k) in the time domain at a certain time k can be reduced.

(Peak reduction signal generator 22: Example 1)
With reference to FIG. 2, the peak reduction signal generator 22 of the first embodiment will be described. The peak reduction signal generation unit 22 according to the first embodiment calculates a dummy signal δ (k) by performing an IFFT on a preset dummy data string Δ (n), and the peak position P of the dummy signal δ (k) is calculated. The cancellation signal d (k) is obtained by adjusting the phase based on the time shift and the peak value s (P), and the cancellation signal d (k) is FFTed to generate the peak reduction signal D (n). By using the peak reduction signal D (n) as dummy data and applying the TR method, the peak of the OFDM signal can be reduced.

  4 is a block diagram illustrating a configuration example of the peak reduction signal generation unit 22 according to the first embodiment, FIG. 5 is a flowchart illustrating a processing example of the peak reduction signal generation unit 22 according to the first embodiment, and FIG. It is a figure explaining the example of a process. The peak reduction signal generator 22-1 of the first embodiment includes IFFT means 30, time shift means 31, phase adjustment means 32, and FFT means 33.

  First, the peak reduction signal generator 22-1 receives the peak position P and the peak value s (P) from the peak detector 21 (step S501). The IFFT means 30 performs IFFT on the preset frequency domain dummy data string Δ (n) to generate a time domain dummy signal δ (k) (step S502). Then, the IFFT means 30 outputs the time domain dummy signal δ (k) to the time shift means 31.

  As described above, the dummy data sequence Δ (n) is a data sequence in which “1” is appropriately arranged on the frequency axis, and complex data may be arranged instead of “1”. As shown in FIG. 6, the time domain dummy signal δ (k) is a signal having a peak at time k = 0 in one symbol from time k = 0 to N−1.

The mathematical formula for converting the frequency domain dummy data sequence Δ (n) into the time domain dummy signal δ (k) by IFFT is as follows.

  The time shift means 31 receives the time domain dummy signal δ (k) from the IFFT means 30 and also receives the peak position P, shifts the time k of the dummy signal δ (k) by the time of the peak position P, A dummy signal δ (k−P) = δ ′ (k) is generated (step S503). Then, the time shift means 31 outputs the time domain dummy signal δ ′ (k) shifted by the time of the peak position P to the phase adjustment means 32.

  As shown in FIG. 6, the dummy signal δ ′ (k) in the time domain is a signal shifted by the time of the peak position P with respect to the dummy signal δ (k), and becomes a signal having a peak at the time position P. .

  The phase adjustment unit 32 receives the time domain dummy signal δ ′ (k) from the time shift unit 31 and the peak value s (P). Then, the phase adjusting means 32 has the phase of the peak value s (P) and the phase of the cancellation signal d (P) (the cancellation signal d (P) in the cancellation signal d (k) to be generated after phase adjustment). In order to be the same (s (P) = d (P)), the phase of the dummy signal δ ′ (k) is adjusted (by phase θ) (rotated) to generate the cancellation signal d (k) ( Step S504). The phase adjustment unit 32 outputs the time domain cancellation signal d (k) to the FFT unit 33.

  As shown in FIG. 6, the time domain cancellation signal d (k) is dummy so that the peak value s (P) is the same as the cancellation signal d (P) (s (P) = d (P)). This signal is obtained by adjusting the phase of the signal δ ′ (k), and has a peak at the time position P.

The mathematical formula for performing the time shift of the peak position P with respect to the dummy signal δ (k) and adjusting the phase θ to be the same as the peak value s (P) to generate the cancellation signal d (k) is as follows: It is as follows.

  From Equation (3), the cancellation signal d (k) and the peak reduction signal D (n) are in a relationship in which the cancellation signal d (k) can be obtained by IFFT of the peak reduction signal D (n). Recognize.

  The FFT unit 33 receives the cancellation signal d (k) from the phase adjustment unit 32, performs FFT on the cancellation signal d (k), and generates a frequency domain peak reduction signal D (n) (step S505). The peak reduction signal D (n) for the region is output to the scaling unit 23 (step S506).

The scaling unit 23 receives the peak reduction signal D (n) generated by the FFT unit 33 and adjusts the level of the peak reduction signal D (n) using the scale value C. As a result, as shown in the following equation, the magnitude of the cancellation signal d (P) at the peak position P in the cancellation signal d (k) can be changed, and the signal s (P) at the peak position P in the signal s (k). ) Can be reduced. The scale value C can be sequentially changed by a variable mechanism such as a volume, in addition to being preset as a constant.

  As described above, according to the peak reduction processing unit 20 including the peak reduction signal generation unit 22-1 of the first embodiment, the IFFT unit 30 of the peak reduction signal generation unit 22-1 appropriately “ IF ”is applied to the dummy data string Δ (n) in which“ 1 ”is arranged to generate a dummy signal δ (k) having a peak at time k = 0, and the time shift unit 31 includes the dummy signal δ (k). The time k is shifted by the time of the peak position P of the OFDM signal obtained by IFFT of the transmission target data, and a new dummy signal δ ′ (k) having a peak at the time position P is generated.

  The phase adjustment unit 32 makes the phase of the peak value s (P) of the OFDM signal obtained by IFFT of the transmission target data the same as the phase of the cancellation signal d (P) (s (P) = d (P)), the phase of the dummy signal δ ′ (k) is adjusted (by phase θ) (rotated) to generate the cancellation signal d (k). Then, the FFT means 33 performs FFT on the cancellation signal d (k) to generate a peak reduction signal D (n).

  Thus, the dummy signal δ (k) having a peak at time k = 0 is generated from the dummy data string Δ (n) by the peak reduction signal generation unit 22-1 of the first embodiment, and the peak position P and the peak Based on the position s (P), a peak reduction signal D (n) for canceling the peak value s (P) is generated.

  Then, the scaling unit 23 divides the peak reduction signal D (n) by the scale value C to generate a peak reduction signal D (n) / C whose level is adjusted, and the AC embedding unit 25 Of the subcarriers of the OFDM signal S (n) obtained by delaying the data to be transmitted by IFFT and a predetermined time, the peak reduction signal D (n) / C The dummy data is embedded to generate a signal S ′ (n), and the IFFT unit 26 performs IFFT on the signal S ′ (n) to generate a time-domain signal s ′ (k) with a reduced peak.

  Thereby, since the data of the OFDM signal S (n) is used as it is without being manipulated, the EVM is not deteriorated by the peak reduction process. In particular, a dummy signal (peak reduction signal D (n) / C) embedded in a subcarrier to which no data is allocated is generated based on the peak position P and the peak value s (P), and the peak reduction amount Since the adjustment is performed with the scale value C for adjusting the EVM, it is possible to effectively suppress the degradation of the EVM by using the dummy signal.

(Peak reduction signal generator 22: Example 2)
Next, referring to FIG. 2, the peak reduction signal generation unit 22 according to the second embodiment will be described. In the second embodiment, the processing of the complex operation in the first embodiment is replaced with processing that does not use the complex operation. The peak reduction signal generation unit 22 according to the second embodiment uses the phase data stored in the phase conversion table to change the phase of the preset dummy data string Δ (n) to the peak position P and the peak value s (P). And the peak reduction signal D (n) is directly generated. By using the peak reduction signal D (n) as dummy data and applying the TR method, the peak of the OFDM signal can be reduced. Further, the second embodiment can reduce the amount of calculation of the peak reduction signal D (n) compared to the first embodiment.

  FIG. 7 is a block diagram illustrating a configuration example of the peak reduction signal generation unit 22 according to the second embodiment. The peak reduction signal generator 22-2 according to the second embodiment includes a signal generator 40 and a memory 41.

  The signal generation means 40 receives the peak position P and the peak value s (P) from the peak detection unit 21, and a preset dummy data string Δ (n) (for example, “1” is arranged on the frequency axis). Data column). Then, the signal generation unit 40 rotates the phase of the dummy data string Δ (n) according to the peak position P and the peak value s (P) using the phase data of the phase conversion table stored in the memory 41. The peak reduction signal D (n) is generated. The signal generation means 40 outputs the peak reduction signal D (n) to the scaling unit 23.

From the formula (3), the relationship between the peak reduction signal D (n), the dummy data string Δ (n), the peak position P, and the phase θ is expressed by the following formula. n = 0 to N-1. The phase θ includes the phase of the peak value s (P) and the phase of the cancellation signal k (P) at the peak position P in the cancellation signal d (k) obtained by IFFT of the peak reduction signal D (n). The phase is obtained by rotating the signal s (k) so as to be the same.

  That is, the signal generation means 40 uses the dummy data string Δ (n), the peak position P, and the phase θ obtained from the peak value s (P), and the peak reduction signal D is expressed by the equation (5). (N) can be calculated.

  From Equation (5), the peak reduction signal D (n) is rotated by (θ) after rotating the phase of the dummy data string Δ (n) by ((−2πn / N) × P)). It can be said that it is a signal (Example 2-1 mentioned later). The peak reduction signal D (n) can also be said to be a signal obtained by rotating the phase of the dummy data string Δ (n) by ((−2πn / N) × P + θ) (Example 2-2 described later).

  Here, in order to cope with the change of the peak position P for each symbol, the phase data (n = 0 to N−1) reflecting the exponential calculation is stored in the memory 41 for all the peak positions P = 0 to N−1. ) Is stored in advance, the signal generation means 40 can read the phase data corresponding to the peak position P from the memory 41 and generate the peak reduction signal D (n).

  However, preparing the phase data for all the peak positions P in the memory 41 extremely increases the capacity of the memory 41 and is difficult to realize.

  Therefore, in the embodiment of the present invention, the memory capacity is reduced by storing in the memory 41 only the phase data at each point when P = 1 when one symbol consists of N samples. N is a positive integer.

  The memory 41 stores a phase conversion table. In the phase conversion table, the phase data (0, 2π / N, 2π × 2 / N) at P = 1 when one symbol is composed of N samples. ,..., 2π (N−1) / N) are stored. The phase data at each point is a phase 2πn / N (n = 0 to N−1) in the case of one rotation between 0 and 2π (0 or more and less than 2π).

  FIG. 8 is a diagram for explaining data stored in the memory 41 in the second embodiment. The phase conversion table in the memory 41 corresponds to the phase rotation amount (−j × (2πn / N) × P) (the exponential function of the second term on the right side of the equation (5)) when the peak position P = 1. The phase data of each point when one symbol is composed of N samples is stored.

  Address 1 has phase data 0 when P = 1 and n = 0 (real part data Dr_0, imaginary part data Di_0), and address 2 has phase data 2π / N when P = 1 and n = 1 (real Part data Dr_1, imaginary part data Di_1),..., Address N includes phase data 2π (N−1) / N when P = 1 and n = N−1 (real part data Dr_N−1, imaginary part Data Di_N-1) are stored respectively.

  The phase data of the phase conversion table stored in the memory 41 may be the real part data and the imaginary part data shown in FIG. 8, or the phase 2πn / N from 0 to 2π (n = 0 to N). -1).

(Peak reduction signal generation unit 22-2 of Example 2-1)
The first peak reduction signal generation unit 22-2 (the peak reduction signal generation unit 22 of Example 2-1) will be described. The peak reduction signal generation unit 22-2 according to the embodiment 2-1 uses the phase data of the phase conversion table stored in the memory 41 to change the phase of the dummy data string Δ (n) according to the peak position P ( −2πn / N), and the phase after the rotation is further rotated by θ according to the peak value s (P), thereby generating the peak reduction signal D (n).

  FIG. 9 is a block diagram illustrating a configuration example of the peak reduction signal generation unit 22-2 of the embodiment 2-1, and FIG. 10 illustrates a processing example of the peak reduction signal generation unit 22-2 of the embodiment 2-1. It is a flowchart to show. FIG. 11 (1) is a diagram illustrating an example of phase data at the peak position P = 2, and FIG. 11 (2) is a diagram illustrating an example of phase data at the peak position P = 3.

  The peak reduction signal generator 22-2 of the embodiment 2-1 includes a signal generator 40-1 and a memory 41. The signal generation unit 40-1 includes a time shift stage 42, a phase specifying stage 43, and a phase adjustment stage 44.

  The peak reduction signal generator 22-2 receives the peak position P and the peak value s (P) from the peak detector 21 (step S1001). Based on the peak position P, the time shift stage 42 specifies a read position (address) for each n when reading phase data from the phase conversion table stored in the memory 41 (step S1002).

  For example, when the peak position P = 1, the time shift stage 42 specifies read positions (addresses) 1 to N corresponding to n = 0 to N−1. In addition, when the peak position P = 2, the time shift stage 42 corresponds to n = 0 to N−1, and the odd number of read positions (addresses) 1 and 1 skipped one by one from the continuous addresses 1 to N. 3,..., N-1, 1, 3,. In addition, when the peak position P = 3, the time shift stage 42 corresponds to n = 0 to N−1, and read positions (addresses) 1, 4, 4, which are skipped every two consecutive addresses 1 to N. ..., N-2, 2, 5, ..., N-1, 3, 6, ... are specified.

  As described above, the time shift stage 42 corresponds to n = 0 to N−1 in the case of the peak position P = p (p is an integer of 1 or more), and every time p−1 among the continuous addresses 1 to N. The skipped reading position (address) is specified.

  Then, the time shift stage 42 reads the phase data at the specified read position (address) from the phase conversion table stored in the memory 41 (step S1003). Here, the phase data read from the phase conversion table stored in the memory 41 corresponds to the exponential function of the second term in the equation (5).

  For example, when the peak position P = 1, the phase data is sequentially read from the specified read positions (addresses) 1 to N corresponding to n = 0 to N−1.

  Further, for example, when the peak position P = 2, as shown in FIG. 11 (1), the phase data is skipped one by one from the continuous addresses 1 to N corresponding to n = 0 to N-1. .., 1, 3,... Are read sequentially. In this case, the time shift stage 42 scans the addresses 1 to N of the phase conversion table stored in the memory 41 twice, and reads the odd read positions (addresses) 1, 3,..., 1, 3,. • Read the phase data sequentially.

  Further, for example, when the peak position P = 3, as shown in FIG. 11B, the phase data is skipped every two of consecutive addresses 1 to N corresponding to n = 0 to N−1. .., 2, 5,..., 3, 6,. In this case, the time shift stage 42 scans the addresses 1 to N of the phase conversion table stored in the memory 41 three times, and reads out positions (addresses) 1, 4,..., 2, 5,. The phase data of 3, 6,.

  That is, in the case of the peak position P = p, the phase data is sequentially read from the read positions (addresses) skipped every p−1 among the continuous addresses 1 to N corresponding to n = 0 to N−1. In this case, the time shift stage 42 scans the addresses 1 to N of the phase conversion table stored in the memory 41 p−1 times, and sequentially reads the phase data at the reading position (address).

  The time shift stage 42 adjusts (rotates) the phase of the dummy data sequence Δ (n) in which “1” is arranged on the frequency axis by the phase of the read phase data, and generates the time shift signal D1 (n). Generate (step S1004). Then, the time shift stage 42 outputs the time shift signal D1 (n) to the phase adjustment stage 44.

  That is, the time shift stage 42 multiplies the dummy data string Δ (n) by the phase data (on the right side of the equation (5), multiplies the first term Δ (n) by the second term exponential function. By performing this process, the phase of the dummy data string Δ (n) is rotated by the phase of the phase data, and the time shift signal D1 (n) is generated.

  The phase specifying stage 43 specifies the phase θ based on the real part and imaginary part data of the peak value s (P) (step S1005). Then, the phase identification stage 43 outputs the phase θ to the phase adjustment stage 44.

  The phase adjustment stage 44 adjusts (rotates) the phase of the time shift signal D1 (n) by the specified phase θ to generate a peak reduction signal D (n) (step S1006). Then, the phase adjustment stage 44 outputs the peak reduction signal D (n) to the scaling unit 23 (step S1007).

  Here, the process of rotating by the phase θ corresponds to the exponential function of the third term in the equation (5). That is, the phase adjustment stage 44 multiplies the time shift signal D1 (n) by the phase data (by performing the calculation of the right side of the equation (5)), thereby changing the phase of the time shift signal D1 (n) to the phase. The peak reduction signal D (n) is generated by rotating the phase of the data.

  In FIG. 9, the time shift stage 42, the phase specifying stage 43, and the phase adjusting stage 44 may be arranged in reverse. In this case, in FIG. 10, the process of steps S1002 to S1004 by the time shift stage 42, the process of step S1005 by the phase specifying stage 43, and the process of step S1006 by the phase adjustment stage 44 are reversed. 42 outputs the peak reduction signal D (n) to the scaling unit 23.

  As described above, according to the peak reduction processing unit 20 including the peak reduction signal generation unit 22-2 of the embodiment 2-1, the memory 41 stores phase data of each point when one symbol is composed of N samples. A phase conversion table including (0, 2π / N, 2π × 2 / N,..., 2π (N−1) / N) is stored. The time shift stage 42 of the peak reduction signal generation unit 22-2 performs every n when reading phase data from the phase conversion table of the memory 41 based on the peak position P of the OFDM signal obtained by IFFT of the transmission target data. As the read position (address), when the peak position P = p, the read position (address) skipped every p-1 among the consecutive addresses 1 to N is specified corresponding to n = 0 to N-1. The phase data at the specified read position (address) is read from the phase conversion table in the memory 41. Then, the time shift stage 42 adjusts (rotates) the phase of the dummy data string Δ (n) by the phase of the read phase data, and generates the time shift signal D1 (n).

  The phase identification stage 43 identifies the phase θ based on the peak value s (P), and the phase adjustment stage 44 adjusts (rotates) the phase of the time shift signal D1 (n) by the phase θ to reduce the peak. A signal D (n) is generated.

  In this manner, the phase of the dummy data string Δ (n) is rotated according to the peak position P using the phase conversion table of the memory 41 by the peak reduction signal generation unit 22-2 of the embodiment 2-1. Then, the phase after the rotation further rotates by the phase θ according to the peak value s (P), thereby generating a peak reduction signal D (n) for canceling the peak value s (P).

  Then, the scaling unit 23 generates a peak reduction signal D (n) / C in which the level of the peak reduction signal D (n) is adjusted, and the AC embedding unit 25 delays the transmission target data by IFFT and a predetermined time. Among the subcarriers of the obtained OFDM signal S (n), dummy data of the peak reduction signal D (n) / C is embedded in the subcarrier position of the AC signal to which no data is assigned, and the signal S ′ (n) The IFFT unit 26 performs IFFT on the signal S ′ (n) to generate a time-domain signal s ′ (k) with a reduced peak.

  Thereby, there exists an effect similar to Example 1. That is, since the data of the OFDM signal S (n) is used without being manipulated, the EVM is not deteriorated by the peak reduction process. In particular, the dummy signal (peak reduction signal D (n) / C) is generated based on the peak position P and the peak value s (P), and is adjusted with the scale value C for adjusting the amount of peak reduction. Therefore, by using the dummy signal, it is possible to effectively suppress the degradation of the EVM.

  The phase conversion table stored in the memory 41 is used as a fixed table regardless of the value of the peak position P. Therefore, since it is not necessary to define the phase data of all the peak positions P in the phase conversion table, the memory capacity can be reduced.

(Peak reduction signal generation part 22-2 of Example 2-2)
The second peak reduction signal generation unit 22-2 (the peak reduction signal generation unit 22 of Example 2-2) will be described. The peak reduction signal generation unit 22-2 according to the embodiment 2-2 uses the phase data of the phase conversion table stored in the memory 41 to change the phase of the dummy data string Δ (n) to the peak position P and the peak value s. The peak reduction signal D (n) is generated by rotating ((−2πn / N) × P + θ) in accordance with (P).

  FIG. 12 is a block diagram illustrating a configuration example of the peak reduction signal generation unit 22-2 according to the embodiment 2-2. FIG. 13 illustrates a processing example of the peak reduction signal generation unit 22-2 according to the embodiment 2-2. It is a flowchart to show. FIG. 14A is a diagram showing phase data when the peak position P = 1, and FIG. 14B is a diagram showing phase data when the peak position P = 1 and the phase θ are adjusted. FIG. 14 (3) is a diagram supplementing the explanation of (2) when the peak position P = 1 and the phase θ are adjusted.

  The peak reduction signal generator 22-2 of the embodiment 2-2 includes a signal generator 40-2 and a memory 41. The signal generating means 40-2 includes a phase specifying stage 43 and a time shift and phase adjusting stage 45.

  The peak reduction signal generator 22-2 receives the peak position P and the peak value s (P) from the peak detector 21 (step S1301). The phase specifying stage 43 specifies the phase θ based on the data of the real part and the imaginary part of the peak value s (P) (step S1302). Then, the phase identification stage 43 outputs the phase θ to the time shift and phase adjustment stage 45.

  The time shift and phase adjustment stage 45 inputs the phase θ from the phase identification stage 43. Further, the time shift and phase adjustment stage 45 specifies a read position (address) for each n when reading phase data from the phase conversion table stored in the memory 41 based on the peak position P (step S1303).

  Specifically, the time shift and phase adjustment stage 45 is similar to the time shift stage 42 shown in FIG. 9, for example, when the peak position P = 1, the read position corresponding to n = 0 to N−1. (Addresses) 1 to N are specified, and when the peak position P = 2, the read positions skipped one by one corresponding to n = 0 to N−1 are specified. When the peak position P = 3, n = A read position (address) skipped every two corresponding to 0 to N−1 is specified.

  The time shift and phase adjustment stage 45 shifts (changes) all the read positions (addresses) for each specified n based on the phase θ (step S1304). Specifically, the time shift and phase adjustment stage 45 shifts by θN / (2π) for the specified read position (address) for each n.

  For example, as shown in FIG. 14 (1), in the phase data in the case of the peak position P = 1, by shifting the frequency corresponding to the phase θ, the peak position P = 1 and phase data adjusted in phase θ are obtained. The position of n = 0 on the frequency axis in FIG. 14 (2) is obtained by shifting the position of n = 0 on the frequency axis in FIG. 14 (1) to the right (or left) by an amount corresponding to the phase θ. .

  In other words, the phase θ can be adjusted by manipulating a certain amount of phase within one symbol, so the read position (address) of the memory 41, that is, the read start position (first read position, n = 0 position) is the phase. By changing according to θ, it is possible to adjust an arbitrary phase θ.

  As shown in FIG. 14 (3), in the process of step S1303 of FIG. 13, based on the peak position P = 1, the read position (address) (read start position) = 1 when n = 0, n = Reading position (address) when 1 = 2, reading position (address) when n = 2 = 3, reading position (address) when n = 3 = 4, reading position (address when n = 4) ) = 5,..., N = N−1. Read position (address) = N is specified.

  In this case, it is assumed that the phase θ = 4π / N has already been specified in the process of step S1302 of FIG. As shown in FIG. 14 (3), in the process of step S1304 in FIG. 13, when the read position (address) amount to be shifted corresponding to the phase θ is θN / (2π) = 3, The read position (address) is read position (address) (read start position) when n = 0, read position (address) when n = 1 = 5,..., N = N−4 Read position (address) = N, read position (address) when n = N−3 = 1, read position (address) when n = N−2, and n = N−1. Read position (address) = 3.

  The time shift and phase adjustment stage 45 reads the phase data of the read position (address) after the shift from the phase conversion table stored in the memory 41 (step S1305). The phase data read from the phase conversion table stored in the memory 41 corresponds to the multiplication result of the exponential function of the second term and the exponential function of the third term in the equation (5).

  For example, the time shift and phase adjustment stage 45 adjusts (rotates) the phase of the dummy data sequence Δ (n) in which “1” is appropriately arranged on the frequency axis by the phase of the read phase data, and reduces the peak. A signal D (n) is generated (step S1306). Then, the time shift and phase adjustment stage 45 outputs the peak reduction signal D (n) to the scaling unit 23 (step S1307).

  In other words, the time shift and phase adjustment stage 45 multiplies the dummy data string Δ (n) by the phase data (by performing the calculation of the right side of the equation (5)), thereby obtaining the dummy data string Δ (n). The phase is rotated by the phase of the phase data to generate the peak reduction signal D (n). As a result, the peak reduction signal D (n) is generated without performing a complex complex operation.

  In FIG. 13, the processing in step S1303 and the processing in step S1304 by the time shift and phase adjustment stage 45 may be reversed. In this case, the time shift and phase adjustment stage 45 obtains the read position shift amount (read start position) based on the phase θ, obtains the read position based on the peak position P, and shifts the shift amount from the read position. A new reading position is specified.

  As described above, according to the peak reduction processing unit 20 including the peak reduction signal generation unit 22-2 of Example 2-2, the phase data of each point when one symbol is composed of N samples is stored in the memory 41. A phase conversion table including (0, 2π / N, 2π × 2 / N,..., 2π (N−1) / N) is stored. The phase identification stage 43 of the peak reduction signal generator 22-2 identifies the phase θ based on the peak value s (P).

  The time shift and phase adjustment stage 45 is a read position (address) for each n when reading phase data from the phase conversion table of the memory 41 based on the peak position P of the OFDM signal obtained by IFFT of the data to be transmitted. In the case of the peak position P = p, corresponding to n = 0 to N−1, the read position (address) skipped every p−1 among consecutive addresses 1 to N is specified, and based on the phase θ. All the read positions (addresses) for each specified n are shifted (changed). Then, the time shift and phase adjustment stage 45 reads the phase data of the read position (address) after the shift from the phase conversion table of the memory 41, and converts the phase of the dummy data string Δ (n) to the phase of the read phase data. Only by adjusting (rotating) the peak reduction signal D (n).

  In this way, the peak reduction signal generator 22-2 of the embodiment 2-2 uses the phase conversion table of the memory 41 to change the phase of the dummy data string Δ (n) to the peak position P and the peak value s (P ) To generate a peak reduction signal D (n).

  Then, the scaling unit 23 generates a peak reduction signal D (n) / C in which the level of the peak reduction signal D (n) is adjusted, and the AC embedding unit 25 delays the transmission target data by IFFT and a predetermined time. Among the subcarriers of the obtained OFDM signal S (n), dummy data of the peak reduction signal D (n) / C is embedded in the subcarrier of the AC signal to which no data is assigned, and the signal S ′ (n) is embedded. Then, the IFFT unit 26 performs IFFT on the signal S ′ (n) to generate a time-domain signal s ′ (k) with a reduced peak.

  Thereby, there exists an effect similar to Example 2-1. That is, the degradation of the EVM can be effectively suppressed, and the memory capacity of the memory 41 for storing the phase conversion table can be reduced.

  In particular, the peak reduction signal generation unit 22-2 of the embodiment 2-2 uses the phase conversion table of the memory 41 to change the phase of the dummy data string Δ (n) to the peak position P and the peak value s (P). Accordingly, the peak reduction signal D (n) is directly generated. As a result, the peak reduction signal D (n) can be generated without performing complex complex operations.

  On the other hand, in the peak reduction signal generator 22-1 of the first embodiment shown in FIG. 4, complex calculation is performed in the time shift unit 31 and the phase adjustment unit 32. That is, the peak reduction signal generation unit 22-2 according to the embodiment 2-2 can reduce the calculation cost as compared with the peak reduction signal generation unit 22-1 according to the first embodiment.

  Therefore, the peak reduction signal generation unit 22-2 of the embodiment 2-2 can reduce the calculation cost when generating the peak reduction signal D (n) without consuming more memory than necessary.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the technical idea thereof. For example, the AC embedding unit 25 shown in FIG. 2 applies the peak reduction signal D (n) / C to the subcarriers of the AC signal to which no data is allocated among the subcarriers of the frequency domain signal S (n). Added dummy data. In the present invention, the subcarriers in which the dummy data of the peak reduction signal D (n) / C is embedded are not limited to the subcarriers of the AC signal, and may be a part of the subcarriers of the AC signal. It may be a subcarrier to which no data is allocated, and may be a position other than the subcarrier of the AC signal.

  The processing of each component from the data mapping unit 10 to the GI adding unit 13 of the OFDM signal transmission device 1 shown in FIG. 1 is realized by an LSI chip that is an integrated circuit mounted on the OFDM signal transmission device 1. You may make it do. These may be individually made into one chip, or a part or all of them may be made into one chip.

  Further, the processing from the peak detection unit 21 to the IFFT unit 26 in the peak reduction processing unit 20 of the OFDM signal transmission device 1 is also realized by an LSI chip that is an integrated circuit mounted on the OFDM signal transmission device 1. Also good. These may be individually made into one chip, or a part or all of them may be made into one chip. For example, the peak reduction signal generation unit 22 may be integrated into one chip.

  Further, instead of the LSI, it may be realized by a chip such as a VLSI or ULSI having a different degree of integration. Furthermore, the present invention is not limited to a chip such as an LSI, and a dedicated circuit or a general-purpose processor may be used, or an FPGA (Field Programmable Gate Array) may be used.

1,100 OFDM signal transmitter 10 Data mapping unit 11 Subcarrier arrangement unit 12 IFFT unit 13 GI addition unit 20 Peak reduction processing unit 21 Peak detection unit 22 Peak reduction signal generation unit 23 Scaling unit 24 Delay correction unit 25 AC embedding unit 26 IFFT section 30 IFFT means 31 Time shift means 32 Phase adjustment means 33 FFT means 40 Signal generation means 41 Memory 42 Time shift stage 43 Phase identification stage 44 Phase adjustment stage 45 Time shift and phase adjustment stage

Claims (6)

In a peak reduction circuit that sets predetermined dummy data to a subcarrier to which data in an OFDM signal in the frequency domain is not allocated, and reduces the peak of the OFDM signal in the time domain,
A peak detector that detects a time position where the amplitude in one symbol in the time-domain OFDM signal is maximum as a peak position, and detects the OFDM signal in the time domain at the peak position as a peak value;
A signal for reducing the peak value detected by the peak detector, and generating a peak reduction signal in a frequency region having a predetermined peak value at the same position as the peak position detected by the peak detector A peak reduction signal generator that
A scaling unit that scales by dividing the peak reduction signal in the frequency domain generated by the peak reduction signal generation unit by a predetermined scale value;
A portion of the scaled peak reduction signal scaled by the scaling unit is the predetermined dummy data, and the dummy data is embedded in a subcarrier to which no data in the OFDM signal in the frequency domain is assigned,
An IFFT unit that performs an IFFT (Inverse Fast Fourier Transform) on the OFDM signal in the frequency domain in which the dummy data is embedded by the embedding unit, and generates an OFDM signal in the time domain in which the peak is reduced;
A peak reduction circuit comprising: The peak reduction circuit of claim 1,
The peak reduction signal generator is
IFFT means for performing IFFT on a frequency domain dummy data string in which predetermined data is arranged on the frequency axis, and generating a time domain dummy signal;
A time shift means for shifting the time of the time domain dummy signal generated by the IFFT means by the time of the peak position detected by the peak detection unit to generate a new time domain dummy signal;
Adjusting the phase of the new time domain dummy signal generated by the time shift means, and generating a time domain cancellation signal; and
FFT means for applying an FFT to the time domain cancellation signal generated by the phase adjustment means to generate a peak reduction signal in the frequency domain,
The phase adjusting means is
The new time domain so that the phase of the peak value detected by the peak detector and the phase of the cancellation signal at the same position as the peak position detected by the peak detector are the same. Adjusting the phase of the dummy signal to generate a cancellation signal in the time domain,
A peak reduction circuit characterized by that. The peak reduction circuit of claim 1,
The peak reduction signal generator is
A memory storing a table containing phase data for each point rotating between 0 and 2π when one symbol is composed of a predetermined number of points;
Using the phase data of the table stored in the memory, the peak position and the peak value detected by the peak detection unit by detecting the phase of the dummy data string in the frequency domain in which predetermined data is arranged on the frequency axis And a signal generation means for generating a peak reduction signal in the frequency domain,
The signal generating means includes
Based on the peak position, a read position when reading the phase data of the table stored in the memory is specified, the phase data of the read position is sequentially read from the table stored in the memory, and the frequency domain A time shift stage that adjusts the phase of the dummy data sequence by the phase of the read phase data and generates a time shift signal in the frequency domain;
A phase identification stage for identifying a phase based on the peak value;
A phase adjustment stage that adjusts the phase of the frequency shift signal in the frequency domain generated by the time shift stage by the phase specified by the phase identification stage, and generates a peak reduction signal in the frequency domain;
A peak reduction circuit characterized by comprising: The peak reduction circuit of claim 1,
The peak reduction signal generator is
A memory storing a table containing phase data for each point rotating between 0 and 2π when one symbol is composed of a predetermined number of points;
Using the phase data of the table stored in the memory, the peak position and the peak value detected by the peak detection unit by detecting the phase of the dummy data string in the frequency domain in which predetermined data is arranged on the frequency axis And a signal generation means for generating a peak reduction signal in the frequency domain,
The signal generating means includes
A phase identification stage for identifying a phase based on the peak value;
Based on the peak position, a read position when reading the phase data of the table stored in the memory is specified, the read position is shifted based on the phase specified by the phase specifying stage, and the memory Sequentially read out the phase data at the read-out position after the shift from the phase conversion table stored in, and adjust the phase of the dummy data string in the frequency domain by the phase of the read out phase data to reduce the peak in the frequency domain A time shift and phase adjustment stage for generating a signal;
A peak reduction circuit characterized by comprising: OFDM signal transmission for mapping the data to be transmitted and placing it on frequency domain subcarriers, performing IFFT (Inverse Fast Fourier Transform) on the frequency domain signal to generate a time domain OFDM signal, and transmitting the OFDM signal In the device
A data mapping unit for performing carrier modulation on the data to be transmitted and mapping it to an IQ axis, and generating a modulated signal;
A subcarrier arrangement unit configured to arrange the modulation signal generated by the data mapping unit on a subcarrier in a frequency domain and generate a signal in a frequency domain;
An IFFT unit that performs IFFT on the frequency domain signal generated by the subcarrier arrangement unit to generate a time domain OFDM signal;
Predetermined dummy data is set to a subcarrier to which data in the frequency domain signal generated by the subcarrier arrangement unit is not allocated, and peaks are reduced from the time domain OFDM signal generated by the IFFT unit. A peak reduction processing unit for generating the generated signal as a new time-domain OFDM signal;
A GI adding unit that adds a GI (guard interval) to the OFDM signal in the new time domain generated by the peak reduction processing unit,
The peak reduction processing unit
A peak detection unit that detects a time position where the amplitude in one symbol in the OFDM signal in the time domain generated by the IFFT unit is maximum as a peak position, and detects the signal at the peak position as a peak value;
A signal for reducing the peak value detected by the peak detection unit, a peak reduction signal of a frequency region having a predetermined peak value at the same position as the peak position detected by the peak detection unit A peak reduction signal generator to generate;
A scaling unit that scales by dividing the peak reduction signal in the frequency domain generated by the peak reduction signal generation unit by a predetermined scale value;
A part of the scaled peak reduction signal scaled by the scaling unit is the predetermined dummy data, and the dummy data is embedded in a subcarrier to which data in the frequency domain signal is not assigned,
An IFFT unit that performs IFFT on the frequency domain signal in which the dummy data is embedded by the embedding unit, and generates a new time domain OFDM signal in which the peak is reduced;
An OFDM signal transmitting apparatus comprising: OFDM signal transmission for mapping the data to be transmitted and placing it on frequency domain subcarriers, performing IFFT (Inverse Fast Fourier Transform) on the frequency domain signal to generate a time domain OFDM signal, and transmitting the OFDM signal In the chip mounted on the device,
The OFDM signal transmitter
A data mapping unit for performing carrier modulation on the data to be transmitted and mapping it to an IQ axis, and generating a modulated signal;
A subcarrier arrangement unit configured to arrange the modulation signal generated by the data mapping unit on a subcarrier in a frequency domain and generate a signal in a frequency domain;
An IFFT unit that performs IFFT on the frequency domain signal generated by the subcarrier arrangement unit to generate a time domain OFDM signal;
Predetermined dummy data is set to a subcarrier to which data in the frequency domain signal generated by the subcarrier arrangement unit is not allocated, and peaks are reduced from the time domain OFDM signal generated by the IFFT unit. A peak reduction processing unit for generating the generated signal as a new time-domain OFDM signal;
A GI adding unit that adds a GI (guard interval) to the OFDM signal in the new time domain generated by the peak reduction processing unit,
The peak reduction processing unit
A peak detection unit that detects a time position where the amplitude in one symbol in the OFDM signal in the time domain generated by the IFFT unit is maximum as a peak position, and detects the signal at the peak position as a peak value;
A signal for reducing the peak value detected by the peak detection unit, a peak reduction signal of a frequency region having a predetermined peak value at the same position as the peak position detected by the peak detection unit A peak reduction signal generator to generate;
A scaling unit that scales by dividing the peak reduction signal in the frequency domain generated by the peak reduction signal generation unit by a predetermined scale value;
A part of the scaled peak reduction signal scaled by the scaling unit is the predetermined dummy data, and the dummy data is embedded in a subcarrier to which data in the frequency domain signal is not assigned,
An IFFT unit that performs IFFT on the frequency domain signal in which the dummy data is embedded by the embedding unit, and generates a new time domain OFDM signal in which the peak is reduced;
If you have
The chip includes at least the peak reduction signal generation unit.