JP2011141804A - Radio communication device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication device and a radio communication method, wherein a circuit scale can be reduced. <P>SOLUTION: A rotation factor for inverse Fourier transformation to be used for an inverse Fourier transformation processing is held at predetermined phase intervals. A fine rotation factor corresponding to a phase smaller than the phase interval is held as a common rotation factor corresponding to a plurality of combinations of the time area sample number of a time area signal to be used in a Fourier transformation processing and the frequency area sample number of a frequency area signal. Then, when the time area signal is input, the rotation factor for inverse Fourier transformation having the nearest phase to the phase of the rotation factor for Fourier transformation to be used in the Fourier transformation processing is obtained and the obtained rotation factor for inverse Fourier transformation is corrected by the fine rotation factor to generate the rotation factor for Fourier transformation. Then, using the generated rotation factor for Fourier transformation, the Fourier transformation processing is performed onto the input time area signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method.

  Conventionally, communication systems using wireless communication devices such as mobile terminal devices and base stations have been used. In recent years, in 3GPP (Third Generation Partnership Project), standardization of LTE (Long Term Evolution), which is one of high-speed data communication specifications, has been promoted.

  In LTE illustrated above, SC-FDMA (Single Carrier-Frequency Division Multiple Access) is used as an uplink radio access scheme. In the communication system using SC-FDMA, when transmitting data, a transmission-side wireless communication apparatus, for example, performs discrete Fourier transform (DFT) processing and inverse discrete Fourier transform (IDFT). Process. Specifically, when performing the DFT process, the wireless communication device multiplies the time domain signal, which is an input signal, by a twiddle factor and accumulates the multiplication results, and when performing the IDFT process, the input signal is an input signal. Multiply the multiplication results by multiplying the frequency domain signal by the twiddle factor. In addition, when receiving data, the receiving-side wireless communication device also performs, for example, discrete Fourier transform processing and inverse discrete Fourier transform processing.

JP 2008-52504 A Special table 2007-513431 gazette JP 2004-13811 A

  However, a communication system such as the above-described LTE has a problem that the circuit scale of the wireless communication device increases. Specifically, since a wireless communication device compliant with LTE performs DFT processing and IDFT processing, it generally holds a DFT processing twiddle factor and an IDFT processing twiddle factor. In addition, for example, when performing inverse Fourier transform processing with different DFT sizes, the wireless communication apparatus holds a DFT processing twiddle factor for each DFT size. For this reason, since the wireless communication apparatus has a storage area capable of storing a huge number of twiddle factors, the circuit scale increases.

  Here, a case where data is transmitted using a physical channel of PUSCH (Physical Uplink Shared Channel) will be described as an example, and a twiddle factor held by the wireless communication apparatus will be described. When transmitting data using PUSCH, the wireless communication device performs DFT processing with a predetermined DFT size. Specifically, in the case of data communication using PUSCH, the DFT size is determined to have a minimum value of 12 and prime factors of 2, 3, and 5. , 36, 48, 60, 72, 96, 108,..., 1152, 1200, etc.

  For this reason, the wireless communication apparatus generally holds a twiddle factor for each DFT size. However, there are actually twiddle factors that can be shared even when the DFT sizes are different. For example, a twiddle factor for DFT size = 1200 is a twiddle factor obtained by dividing 2π by 1200, and thus includes a twiddle factor for DFT size = 300, 600. Thus, the wireless communication device holds a total of 9264 twiddle factors for at least DFT size = 648, 720, 768, 864, 900, 960, 972, 1080, 1152, 1200. In addition, the wireless communication device also holds 2048 twiddle factors for IDFT processing. That is, the LTE-compliant wireless communication device generally holds, for example, 9264 + 2048 = 11312 twiddle factors. In this way, the wireless communication apparatus holds a twiddle factor for each DFT size, and thus holds a huge number of twiddle factors.

  The disclosed technology has been made in view of the above, and an object thereof is to provide a wireless communication apparatus and a wireless communication method capable of reducing the circuit scale.

  In one aspect, the wireless communication device disclosed in the present application identifies, for each of a plurality of phases having a constant phase difference, a twiddle factor storage unit that stores a twiddle factor corresponding to the phase, and a sampling point of a time domain signal A micro-rotation factor corresponding to phase specifying information that is a combination of a time-domain sample number to be performed and a frequency-domain sample number for identifying a sample point of a frequency domain signal, and corresponding to a phase smaller than the phase difference When a micro-rotation factor storage unit that stores a factor for each of a plurality of phase specifying information and a time domain signal is input, the phase specified by the phase specifying information is set for each phase specifying information in the time domain signal. An acquisition unit that acquires the twiddle factor of the closest phase from the twiddle factor storage unit, and for each of the phase identification information, a minute twiddle factor corresponding to the phase identification information A correction unit that corrects the twiddle factor acquired by the acquisition unit using the acquired micro twiddle factor obtained from the storage unit, and the input time domain signal using the twiddle factor corrected by the correction unit. And a Fourier transform unit for performing Fourier transform processing.

  According to one aspect of the wireless communication device disclosed in the present application, there is an effect that the circuit scale can be reduced.

FIG. 1 is a block diagram illustrating a configuration example of a wireless communication apparatus according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration example of a wireless communication apparatus according to the second embodiment. FIG. 3 is a block diagram illustrating a configuration example of a transmission processing unit according to the second embodiment. FIG. 4 is a diagram for explaining a minute twiddle factor in the second embodiment. FIG. 5 is a diagram illustrating an example of a micro-rotation factor storage unit for DFT size 1200. FIG. 6 is a flowchart illustrating an example of a transmission processing procedure performed by the transmission processing unit according to the second embodiment. FIG. 7 is a flowchart illustrating an example of the DFT processing procedure performed by the transmission processing unit according to the second embodiment. FIG. 8 is a block diagram illustrating a configuration example of a transmission processing unit according to the third embodiment. FIG. 9 is a diagram for explaining a minute twiddle factor in the third embodiment. FIG. 10 is a flowchart illustrating an example of the DFT processing procedure performed by the transmission processing unit according to the third embodiment.

  Embodiments of a wireless communication apparatus and a wireless communication method disclosed in the present application will be described below in detail with reference to the drawings. Note that the wireless communication device and the wireless communication method disclosed in the present application are not limited to the embodiments.

  First, the configuration of the wireless communication apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration example of a wireless communication apparatus according to the first embodiment. In FIG. 1, a part that performs a part of transmission processing by the wireless communication device 10 is illustrated.

  As illustrated in FIG. 1, the wireless communication device 10 according to the first embodiment includes a twiddle factor storage unit 11, a minute twiddle factor storage unit 12, an acquisition unit 13, a correction unit 14, and a Fourier transform unit 15. .

  The twiddle factor storage unit 11 stores a twiddle factor corresponding to the phase for each of a plurality of phases having a constant phase difference. The micro twiddle factor storage unit 12 includes a plurality of combinations of time domain sample numbers for identifying time domain signal sample points and frequency domain sample numbers for identifying frequency domain signal sample points (hereinafter referred to as “phase identification information”). The common twiddle factor corresponding to (may be described) is stored. Specifically, the micro twiddle factor storage unit 12 uses a micro twiddle factor corresponding to a phase smaller than the phase difference of the twiddle factors stored in the inverse Fourier transform twiddle factor storage unit 11 as a common twiddle factor, It memorize | stores for every some phase specific information.

  When a time domain signal is input, the acquisition unit 13 acquires, from the twiddle factor storage unit 11, a twiddle factor having a phase closest to the phase identified by the phase identification information for each phase identification information in the time domain signal. To do.

  For each phase specifying information, the correction unit 14 acquires a micro twiddle factor corresponding to the phase specifying information from the micro twiddle factor storage unit 12, and uses the acquired micro twiddle factor to obtain the twiddle factor acquired by the acquiring unit 13. to correct. And the Fourier-transform part 15 performs a Fourier-transform process with respect to the input time domain signal using the rotation factor correct | amended by the correction | amendment part 14. FIG.

  As described above, the wireless communication device 10 according to the first embodiment holds minute twiddle factors corresponding to a plurality of pieces of phase specifying information without holding a Fourier transform twiddle factor. And the radio | wireless communication apparatus 10 produces | generates the rotation factor for Fourier transformation by correct | amending the rotation factor for inverse Fourier transformation using this micro rotation factor.

  Thereby, the wireless communication apparatus 10 according to the first embodiment can perform the Fourier transform process without holding a huge number of twiddle factors. For this reason, the wireless communication apparatus 10 according to the first embodiment can reduce the circuit scale, and as a result, can reduce power consumption.

  Next, the wireless communication device described in the first embodiment will be described using a specific example. In the second embodiment, an example will be described in which the wireless communication device described in the first embodiment is applied to a mobile communication system whose communication standard is LTE. Also, in the following second embodiment, a wireless communication apparatus and a wireless communication method disclosed in the present application will be described using a case where data transmission is performed using PUSCH as an example.

[Configuration of Wireless Communication Device According to Second Embodiment]
First, the configuration of the wireless communication apparatus according to the second embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration example of a wireless communication apparatus according to the second embodiment. The wireless communication device 20 illustrated in FIG. 2 is, for example, a portable terminal device that conforms to the LTE standard, and performs wireless communication with the base station 1. As illustrated in FIG. 2, the wireless communication device 20 includes a reception antenna 21, a transmission antenna 22, a wireless unit 23, an upper layer 24, and a baseband processing unit 25.

  The receiving antenna 21 is an antenna that receives a signal from the outside. For example, the receiving antenna 21 receives a signal transmitted from the base station 1. The transmission antenna 22 is an antenna that transmits a signal to the outside. For example, the transmission antenna 22 transmits a signal to the base station 1. Note that the wireless communication device 20 may include a transmission / reception antenna that shares a reception antenna and a transmission antenna.

  The radio unit 23 transmits and receives radio signals via the reception antenna 21 and the transmission antenna 22. For example, the wireless unit 23 performs wireless processing such as A / D (Analog / Digital) conversion on the signal received from the reception antenna 21. Further, for example, the radio unit 23 performs radio processing such as D / A (Digital / Analog) conversion on a signal input from the transmission processing unit 200 described later, and the signal after the radio processing is transmitted to the transmission antenna 22. To the base station 1.

  The upper layer 24 performs various processes based on the received data when the received received data is input from the decoding unit 27 described later. For example, when the received data is mail data, the upper layer 24 stores the received data in a predetermined storage area.

  Moreover, when transmitting data to the outside such as the base station 1, the upper layer 24 generates transmission data and outputs the generated transmission data to the encoding unit 28. For example, when data is transmitted by the wireless communication device 20 using a physical channel of PUSCH, the upper layer 24 generates transmission data based on, for example, a user operation.

  The baseband processing unit 25 performs baseband processing on transmission data and reception data. As illustrated in FIG. 2, the baseband processing unit 25 includes a reception processing unit 26, a decoding unit 27, an encoding unit 28, and a transmission processing unit 200.

  The reception processing unit 26 performs various reception processes on the reception data input from the wireless unit 23. For example, the reception processing unit 26 performs CP (Cyclic Prefix) deletion processing, demodulation processing, and the like on the reception data input from the wireless unit 23. The decoding unit 27 decodes the reception data input from the reception processing unit 26.

  The encoding unit 28 adds an error correction code to the transmission data input from the upper layer 24. The transmission processing unit 200 performs various transmission processes on the transmission data to which the error correction code is added by the encoding unit 28. The processing by the transmission processing unit 200 will be specifically described with reference to FIG.

[Configuration of Transmission Processing Unit in Second Embodiment]
Next, the configuration of the transmission processing unit 200 according to the second embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration example of the transmission processing unit 200 according to the second embodiment. As illustrated in FIG. 3, the transmission processing unit 200 according to the second embodiment includes a transmission data generation unit 210, a DFT processing unit 220, a subcarrier mapping unit 230, an IDFT twiddle factor storage unit 240, and an IDFT processing unit 250. A CP (Cyclic Prefix) insertion unit 261, a subcarrier shift unit 262, a minute twiddle factor storage unit 270, a selection control unit 280, and a complex multiplier 290.

  When data is input from the encoding unit 28, the transmission data generation unit 210 modulates the data to generate transmission data. For example, the transmission data generation unit 210 performs modulation processing using a modulation scheme such as BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying).

  The DFT processing unit 220 converts the time domain data input from the transmission data generation unit 210 into frequency domain data. Specifically, the DFT processing unit 220 includes a data storage memory 221 and a DFT calculation unit 222 as shown in FIG.

  The data storage memory 221 is a storage device that stores various data. Specifically, the data storage memory 221 stores time domain data input from the transmission data generation unit 210. In addition, the data storage memory 221 stores the result of the Fourier transform performed by the DFT operation unit 222 described later.

  The DFT operation unit 222 performs a Fourier transform process on the data input from the transmission data generation unit 210. Specifically, the DFT operation unit 222 performs an operation represented by the following equation (1).

In the above formula (1), X (k) represents frequency domain data after Fourier transform. X (n) represents time domain data before Fourier transform. N _DFT represents the DFT size. K indicates a frequency domain sample number for identifying a sample point of the frequency domain signal. N represents a time domain sample number for identifying a sample point of the time domain signal. Note that k and n take values from “0” to “N _DFT −1”.

  The DFT operation unit 222 acquires time-domain data represented by x (n) from the data storage memory 221 when performing the operation of the above formula (1). In addition, the DFT operation unit 222 acquires, from the complex multiplier 290, the twiddle factor represented by the following expression (2) among the above expression (1).

  In this way, the DFT operation unit 222 performs a Fourier transform process on the data stored in the data storage memory 221 using the acquired x (n) and the twiddle factor. As a result, the DFT operation unit 222 converts the time domain data input from the transmission data generation unit 210 into frequency domain data.

  The subcarrier mapping unit 230 maps the frequency domain data input from the DFT processing unit 220 to subcarriers. Specifically, the subcarrier mapping unit 230 acquires the calculation result of the Fourier transform processing by the DFT calculation unit 222 from the data storage memory 221 and maps the acquired data to the subcarrier.

  The IDFT twiddle factor storage unit 240 stores a twiddle factor for inverse Fourier transform, which is a twiddle factor used for inverse Fourier transform processing. Specifically, the IDFT twiddle factor storage unit 240 stores N inverse Fourier transform twiddle factors having an IDFT size. Since the wireless communication device 20 according to the second embodiment conforms to the LTE standard, the IDFT size is “2048”. Therefore, the IDFT twiddle factor storage unit 240 according to the second embodiment stores 2048 twiddle factors obtained by dividing 2π by 2048.

  The IDFT processing unit 250 converts the frequency domain data mapped to the subcarriers by the subcarrier mapping unit 230 into time domain data. Specifically, the IDFT processing unit 250 includes a data storage memory 251 and an IDFT calculation unit 252 as shown in FIG.

  The data storage memory 251 is a storage device that stores various data. Specifically, the data storage memory 251 stores frequency domain data mapped to subcarriers by the subcarrier mapping unit 230. Further, the data storage memory 251 stores the calculation result of the inverse Fourier transform process by the IDFT calculation unit 252 described later.

  The IDFT calculation unit 252 performs an inverse Fourier transform process on the data mapped to the subcarriers by the subcarrier mapping unit 230. Specifically, the IDFT calculation unit 252 performs a calculation represented by the following formula (3).

In the above formula (3), x (n) represents time domain data after inverse Fourier transform. X (k) indicates frequency domain data before inverse Fourier transform. N _IDFT indicates the IDFT size. k and n take values from “0” to “N _IDFT −1”.

  The IDFT calculation unit 252 acquires the data in the frequency domain represented by X (k) from the data storage memory 251 when performing the calculation of the above formula (3). Further, the IDFT calculation unit 252 acquires the inverse Fourier transform twiddle factor represented by the following formula (4) from the formula (3) from the IDFT twiddle factor storage unit 240.

  In this way, the IDFT calculation unit 252 performs an inverse Fourier transform process on the data stored in the data storage memory 251 using the acquired X (k) and the twiddle factor. Accordingly, the IDFT calculation unit 252 converts the frequency domain data mapped to the subcarriers by the subcarrier mapping unit 230 into time domain data.

  The CP insertion unit 261 inserts the CP at the end of the time domain data input from the IDFT processing unit 250 as a CP, and inserts the CP at the beginning of the time domain data. The subcarrier shift unit 262 performs frequency shift by “½” of the bandwidth of each subcarrier by multiplying the data into which the CP is inserted by the CP insertion unit 261 by a twiddle factor. Then, the subcarrier shift unit 262 outputs the time domain data subjected to the subcarrier shift process to the radio unit 23.

  The micro twiddle factor storage unit 270 stores a common micro twiddle factor corresponding to a plurality of combinations in association with a plurality of combinations of the time domain sample number n and the frequency domain sample number k used at the time of Fourier transform processing. . Here, the “common micro twiddle factor” means the phase of the Fourier transform twiddle factor represented by the above formula (2) and the IDFT twiddle factor storage unit 240 closest to the phase of the Fourier transform twiddle factor. The twiddle factor corresponding to the phase difference from the phase of the twiddle factor for the inverse Fourier transform is shown. Hereinafter, a combination of the time domain sample number n and the frequency domain sample number k used in the Fourier transform process may be referred to as “phase identification information”.

  The above minute rotation factor will be described more specifically. As described above, the wireless communication device 20 includes the IDFT twiddle factor storage unit 240. The IDFT twiddle factor storage unit 240 stores the IDFT twiddle factor used during the inverse Fourier transform process. In the second embodiment, since the IDFT size is “2048”, the IDFT twiddle factor storage unit 240 stores 2048 IDFT twiddle factors obtained by dividing 2π by 2048.

  In the second embodiment, the case where data transmission is performed using PUSCH is taken as an example, and the DFT operation unit 222 performs Fourier transform processing using any one of 34 types of DFT sizes. Specifically, such DFT sizes are 12, 24, 36, 48, 60, 72, 96, 108, 120, 144, 180, 192, 216, 240, 288, 300, 324, 360, 384, 432, 480,..., 1080, 1152, 1200, etc.

  For this reason, the wireless communication apparatus generally holds a DFT twiddle factor for each of 34 types of DFT sizes. However, there are DFT twiddle factors that can be shared even when the DFT sizes are different. Therefore, the wireless communication device generally holds at least the DFT twiddle factors for DFT size = 648, 720, 768, 864, 900, 960, 972, 1080, 1152, 1200. Holding all such DFT twiddle factors increases the circuit scale of the wireless communication device.

  Therefore, the wireless communication device 20 according to the second embodiment does not hold the DFT twiddle factor, and does not include the phase of the DFT twiddle factor used during the Fourier transform process and the phase of the IDFT twiddle factor closest to the phase. Holds a small twiddle factor corresponding to the phase difference. Such a small twiddle factor may be the same value for several DFT twiddle factors. This will be specifically described with reference to FIG. FIG. 4 is a diagram for explaining a minute twiddle factor in the second embodiment.

  In the example shown in FIG. 4, it is assumed that the DFT twiddle factor used in the Fourier transform process is “X11”. Also, of the IDFT twiddle factors stored in the IDFT twiddle factor storage unit 240, the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor “X11” is “Y11”. It is assumed that the minute twiddle factor corresponding to the phase difference between the DFT twiddle factor “X11” and the IDFT twiddle factor “Y11” is “C11”.

  In the example shown in FIG. 4, it is assumed that the DFT twiddle factor used in the Fourier transform process is “X12”. Further, of the IDFT twiddle factors stored in the IDFT twiddle factor storage unit 240, the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor “X12” is “Y12”. It is assumed that the minute twiddle factor corresponding to the phase difference between the DFT twiddle factor “X12” and the IDFT twiddle factor “Y12” is “C11”.

  In the example shown in FIG. 4, it is assumed that the DFT twiddle factor used in the Fourier transform process is “X13”. Further, of the IDFT twiddle factors stored in the IDFT twiddle factor storage unit 240, the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor “X13” is “Y13”. It is assumed that the minute twiddle factor corresponding to the phase difference between the DFT twiddle factor “X13” and the IDFT twiddle factor “Y13” is “C11”.

  As described above, the minute twiddle factor corresponding to the phase difference between the predetermined DFT twiddle factor and the predetermined IDFT twiddle factor may have the same value depending on the combination of the DFT twiddle factor and the IDFT twiddle factor. . The DFT twiddle factor is specified by phase specifying information that is a combination of a time domain sample number n and a frequency domain sample number k used during the Fourier transform process. Therefore, the minute twiddle factor storage unit 270 according to the second embodiment stores a common minute twiddle factor corresponding to the plurality of phase specifying information in association with the plurality of phase specifying information. For example, in the example illustrated in FIG. 4, the minute twiddle factor storage unit 270 holds only one common minute twiddle factor “C11”. Further, as in the example shown in FIG. 4, even when the minute twiddle factor “C11” is the same value, “the phase of the DFT twiddle factor> the phase of the IDFT twiddle factor” and “the DFT twiddle factor” There is a case where <phase of ID <phase of twiddle factor for IDFT>. The minute twiddle factor storage unit 270 in the second embodiment also stores code information indicating the magnitude relationship between the phase of the DFT twiddle factor and the phase of the IDFT twiddle factor. Such “code information” corresponds to a “code pattern” described later.

  As shown in FIG. 3, the minute twiddle factor storage unit 270 is provided for each DFT size, such as the minute twiddle factor storage unit 271-1 for DFT size 1200 and the minute twiddle factor storage unit 271-2 for DFT size 1152. Stores the micro-rotation factor. Specifically, the minute twiddle factor storage unit 271-1 for DFT size 1200 stores a minute twiddle factor used when Fourier transform is performed with DFT size = 1200, 600 or the like. Similarly, each of the small twiddle factor storage units 271-2 to 271-10 is used when Fourier transform is performed from DFT size = 1152, 1080, 972, 960, 900, 864, 768, 720, 648, and the like. Memorize the micro-turn factor.

  Next, the micro twiddle factor storage unit 271-1 for DFT size 1200 will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of the minute twiddle factor storage unit 271-1 for the DFT size 1200. As shown in FIG. 5, the DFT size 1200 micro-rotation factor storage unit 271-1 includes items such as “phase identification information”, “micro-rotation factor”, “code pattern”, and “address”.

  The phase specifying information “m” indicates a value specified by the time domain sample number n and the frequency domain sample number k used when Fourier transform processing is performed by the DFT operation unit 222. Specifically, the DFT operation unit 222 uses a twiddle factor represented by the following equation (5) when performing the Fourier transform process with DFT size = 1200.

  The phase identification information “m” corresponds to the remainder result represented by “n · k mod 1200”, for example, as shown in the above equation (5). Alternatively, the phase identification information “m” may be, for example, a multiplication result of the time domain sample number n and the frequency domain sample number k. Note that the phase identification information “m” in the second embodiment is assumed to be the above-described multiplication result.

  Further, the micro-rotation factor storage unit 271-1 for DFT size 1200 stores “P1” or “P2” as a code pattern for each column of the phase specifying information “m”. Such “P1” and “P2” correspond to an item “code pattern” described later. For example, in the example illustrated in FIG. 5, when the phase identification information “m” is “0 to 37”, the code pattern is “P1”. For example, when the phase specifying information “m” is “38 to 75”, the code pattern is “P2”. A process using the code pattern P1 or P2 will be described later.

  The small twiddle factor “A” is a rotation corresponding to the phase difference between the phase of the DFT twiddle factor specified by the phase identification information “m” and the phase of the IDFT twiddle factor closest to the phase of the DFT twiddle factor. Indicates the factor. Here, the DFT size 1200 minute twiddle factor storage unit 271-1 stores only one common minute twiddle factor “A” corresponding to a plurality of pieces of phase specifying information “m”. For example, in the example shown in FIG. 5, when the phase specifying information “m” is “1, 74, 76, 149,... 1124, 1126, 1199”, the minute twiddle factor “A” is “352”. It is. In such a case, the minute twiddle factor storage unit 271-1 for the DFT size 1200 does not hold the minute twiddle factor “352” for each phase specifying information “m”, but “m” = “1, 74, .., 1199 ”, one micro-rotation factor“ 352 ”is held.

  5 corresponds to “A” represented by the following expression (6).

DFT size 1200 for microspheroidal factor storage unit 271-1, since stores microspheroidal factor for DFT size = 1200, _{N DFT} in the above formula (6) is "1200". In FIG. 5, to simplify the description, an example is shown in which the minute twiddle factor storage unit 271-1 for DFT size 1200 holds the minute twiddle factor “A”. However, in reality, the micro-rotation factor storage unit 271-1 for DFT size 1200 stores the calculation result of the above formula (6). That is, the minute twiddle factor storage unit 271-1 for the DFT size 1200 illustrated in FIG. 5 stores the calculation result obtained by substituting the minute twiddle factor “A” into the above formula (6) in the minute twiddle factor “A”.

  The code patterns “P1” and “P2” indicate the codes of the micro-rotation factor. For example, in the example shown in FIG. 5, when the phase specifying information “m” = “1”, the code pattern is “P1”. This indicates that the sign of the micro-rotation factor “352” corresponding to the phase specifying information “m” = “1” is “+” stored in the sign pattern “P1”. For example, when the phase specifying information “m” = “2”, the code pattern is “P1”. This indicates that the code of the minute twiddle factor “496” corresponding to the phase specifying information “m” = “2” is “−” stored in the code pattern “P1”. For example, when the phase specifying information “m” = “74”, the code pattern is “P2”. This indicates that the sign of the micro-rotation factor “352” corresponding to the phase specifying information “m” = “74” is “−” stored in the sign pattern “P2”.

  “Address” indicates a memory address where a micro-rotation factor is stored. In the example illustrated in FIG. 5, the DFT size 1200 minute twiddle factor storage unit 271-1 stores the minute twiddle factor “352” at the address “0” and the minute twiddle factor “496” at the address “1”. An example is shown.

  The DFT size 1152 minute twiddle factor storage unit 271-2 and the DFT size 1080 minute twiddle factor storage unit 271-3 shown in FIG. 3 are also associated with a plurality of pieces of phase specifying information “m”. Only one micro-rotation factor is held.

  Returning to FIG. 3, the minute twiddle factor storage unit 270 includes a selector 272. The selector 272 acquires the minute twiddle factor from the minute twiddle factor storage units 271-1 to 271-10 in accordance with an instruction from the selection control unit 280 described later, and outputs the obtained minute twiddle factor to the complex multiplier 290.

  The selection control unit 280 selects the IDFT twiddle factor used by the IDFT calculation unit 252 from the IDFT twiddle factor storage unit 240 when the inverse Fourier transform process is performed by the IDFT calculation unit 252. Further, the selection control unit 280 selects a DFT twiddle factor used by the DFT operation unit 222 when the DFT operation unit 222 performs Fourier transform processing. The DFT selection process by the selection control unit 280 will be specifically described below.

  First, the selection control unit 280, from the IDFT twiddle factor storage unit 240, has a phase closest to the phase of the DFT twiddle factor specified by the combination of the frequency domain sample number k and the time domain sample number n to be subjected to Fourier transform processing. Select a twiddle factor for IDFT with The selection control unit 280 instructs the IDFT twiddle factor storage unit 240 to output the selected IDFT twiddle factor to the complex multiplier 290.

  Subsequently, the selection control unit 280 performs the minute rotation corresponding to the phase specifying information m calculated from the minute rotation factor storage units 271-1 to 271-10 by the combination of the frequency domain sample number k and the time domain sample number n. Select factors and sign patterns. At this time, the selection control unit 280 selects a micro twiddle factor and a code pattern from the micro twiddle factor storage units 271-1 to 271-10 corresponding to the DFT size. For example, when Fourier transform processing is performed by “DFT = 1200”, “DFT = 600”, or the like by the DFT operation unit 222, the selection control unit 280 performs a minute operation from the minute rotation factor storage unit 271-1 for the DFT size 1200. Select the twiddle factor and sign pattern. Further, for example, when the Fourier transform processing is performed by “DFT = 1152” by the DFT operation unit 222, the selection control unit 280 receives the minute twiddle factor and code pattern from the minute twiddle factor storage unit 271-2 for the DFT size 1152. Select. The selection control unit 280 instructs the selector 272 to output the minute twiddle factor selected in this way to the complex multiplier 290. At this time, if the selected code pattern is “−”, the selection control unit 280 outputs to the complex multiplier 290 a small twiddle factor obtained by inverting the sign of the Q component to the selector 272. Instruct.

  The complex multiplier 290 is a complex multiplier. The complex multiplier 290 according to the second embodiment performs complex multiplication of the IDFT twiddle factor selected by the selection control unit 280 in the IDFT twiddle factor storage unit 240 and the minute twiddle factor output from the selector 272. In other words, the complex multiplier 290 corrects the IDFT twiddle factor selected by the selection control unit 280 using the minute twiddle factor output from the selector 272. Thereby, the complex multiplier 290 can generate the DFT twiddle factor used by the DFT operation unit 222. Then, complex multiplier 290 outputs the generated DFT rotation factor to DFT operation unit 222.

  For example, in the example illustrated in FIG. 4, the complex multiplier 290 receives the IDFT twiddle factor “Y11” from the IDFT twiddle factor storage unit 240 and the minute twiddle factor “C11” from the selector 272. To do. In such a case, the complex multiplier 290 can generate the DFT twiddle factor “X11” by performing complex multiplication of the IDFT twiddle factor “Y11” and the minute twiddle factor “C11”. Similarly, the complex multiplier 290 can generate the DFT twiddle factor “X12” by complex multiplication of the IDFT twiddle factor “Y12” and the minute twiddle factor “C11”. Also, the complex multiplier 290 generates the DFT twiddle factor “X13” by performing complex multiplication of the IDFT twiddle factor “Y13” and the minute twiddle factor “C11” in which the sign of the Q component is inverted. Can do.

  Here, the processing by the selection control unit 280 and the complex multiplier 290 described above will be described with a specific example. In the following description, it is assumed that the DFT operation unit 222 performs the Fourier transform process with DFT size = 1200. In addition, it is assumed that the various information stored in the minute twiddle factor storage unit 271-1 for DFT size 1200 is in the state shown in FIG.

  First, the case where the phase identification information “m” = “0” is described as an example. For example, when the time domain sample number “n” = “0” and the frequency domain sample number “k” = “0”, the phase specifying information “m” = “0”. In such a case, the DFT twiddle factor used by the DFT operation unit 222 is expressed by the following equation (7).

  In this case, the selection control unit 280 selects an IDFT twiddle factor having a phase closest to the phase of the DFT twiddle factor represented by the above equation (7) from the IDFT twiddle factor storage unit 240. For example, the selection control unit 280 multiplies “1200”, which is the DFT size shown in the equation (7), by “2048/1200”, and multiplies “2π · 0” by “2048/1200”. , IDFT twiddle factors are selected. The multiplication result is represented by the following equation (8).

  Then, the selection control unit 280 instructs the IDFT twiddle factor storage unit 240 to output the IDFT twiddle factor represented by the above equation (8) to the complex multiplier 290. The IDFT twiddle factor storage unit 240 that has received this instruction outputs the IDFT twiddle factor expressed by the above equation (8) to the complex multiplier 290.

  Here, the phase of said Formula (7) and said Formula (8) is the same value. That is, the IDFT twiddle factor is a DFT twiddle factor used in the DFT calculation unit 222 even if it is not corrected by the minute twiddle factor. Therefore, the selection control unit 280 outputs a small twiddle factor to the complex multiplier 290 to the selector 272 when the phases of the DFT twiddle factor and the IDFT twiddle factor are the same value as in the above example. Instruct not to.

  Then, complex multiplier 290 outputs the IDFT twiddle factor input from IDFT twiddle factor storage unit 240 to DFT operation unit 222. The DFT operation unit 222 performs Fourier transform processing using the IDFT twiddle factor input from the complex multiplier 290 as the DFT twiddle factor.

  In the above example, the selection control unit 280 does not output the minute twiddle factor to the complex multiplier 290 to the selector 272 when the phase of the above formula (7) and the above formula (8) are the same value. Instructed. However, the selection control unit 280 outputs a small twiddle factor “1” to the complex multiplier 290 to the selector 272 when the above expression (7) and the above expression (8) are the same value. You may instruct.

  Next, the case where the phase identification information “m” = “1” is described as an example. When the phase identification information “m” = “1”, the DFT twiddle factor used by the DFT calculation unit 222 is expressed by the following equation (9).

  In this case, the selection control unit 280 selects the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor represented by the above equation (9) from the IDFT twiddle factor storage unit 240. For example, the selection control unit 280 multiplies “1200”, which is the DFT size shown in the above equation (9), by “2048/1200”, and multiplies “2π · 1” by “2048/1200”. , IDFT twiddle factors are selected. The multiplication result is expressed by the following equation (10).

  Here, the selection control unit 280 replaces “1.7706” in the equation (10) with an integer value by rounding off, for example. Here, “1.7706” is replaced with “2”. For this reason, the said Formula (10) is represented by the following formula | equation (11).

  Then, the selection control unit 280 instructs the IDFT twiddle factor storage unit 240 to output the IDFT twiddle factor represented by the above equation (11) to the complex multiplier 290.

  Subsequently, the selection control unit 280 selects a micro twiddle factor and a code pattern corresponding to the phase specifying information “m” = “1” from the micro twiddle factor storage unit 271-1 for DFT size 1200. As shown in FIG. 5, the micro-rotation factor “A” corresponding to the phase specifying information “m” = “1” is “352”, and the code pattern is “P1” = “+”. As described above, the minute twiddle factor storage unit 271-1 for the DFT size 1200 has an operation value obtained by substituting “352” into “A” in the above equation (6), as shown in the following equation (12). keeping.

  Therefore, the selection control unit 280 instructs the selector 272 to output the minute twiddle factor expressed by the above equation (12) to the complex multiplier 290. Since the code pattern corresponding to the phase identification information “m” = “1” is “+”, the selection control unit 280 does not instruct the selector 272 to invert the code.

  The complex multiplier 290 performs complex multiplication of the minute twiddle factor input from the selector 272 and the IDFT twiddle factor input from the IDFT twiddle factor storage unit 240. Specifically, complex multiplication represented by the following equation (13) is performed.

  Here, the calculation result of the formula (13) is the following formula (14).

  In this way, complex multiplier 290 generates a DFT twiddle factor. Then, the DFT operation unit 222 outputs the DFT twiddle factor represented by the above equation (14) to the DFT operation unit 222. The DFT calculation unit 222 performs a Fourier transform process using the DFT rotation factor input from the complex multiplier 290.

  Note that the transmission data generation unit 210, the DFT operation unit 222, the subcarrier mapping unit 230, the IDFT operation unit 252, the CP insertion unit 261, the subcarrier shift unit 262, and the selection control unit 280 illustrated in FIG. It is. Examples of the electronic circuit include, for example, an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), or a central processing unit (CPU) or a micro processing unit (MPU). The data storage memory 221, the data storage memory 251, the IDFT twiddle factor storage unit 240, and the minute twiddle factor storage unit 270 shown in FIG. 3 are, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash A storage device such as a memory.

[Transmission Processing Procedure by Transmission Processing Unit in Embodiment 2]
Next, the procedure of transmission processing by the transmission processing unit 200 according to the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating an example of a transmission processing procedure performed by the transmission processing unit 200 according to the second embodiment.

  As illustrated in FIG. 6, when data transmission is performed by the wireless communication device 20 (Yes in Step S101), the transmission data generation unit 210 generates transmission data by performing, for example, modulation processing (Step S102). .

  Subsequently, the DFT processing unit 220 and the selection control unit 280 perform a Fourier transform process on the transmission data generated by the transmission data generation unit 210 (step S103). Note that the procedure of Fourier transform processing by the DFT processing unit 220 and the selection control unit 280 will be described later with reference to FIG.

  Subsequently, the subcarrier mapping unit 230 maps the frequency domain data that has been subjected to the Fourier transform processing by the DFT processing unit 220 to the subcarrier (step S104). Subsequently, the IDFT processing unit 250 performs an inverse Fourier transform process on the frequency domain data mapped to the subcarriers by the subcarrier mapping unit 230 (step S105). Note that the IDFT processing unit 250 may perform any inverse Fourier transform processing of IDFT processing or IFFT processing.

  Subsequently, the CP insertion unit 261 inserts the CP into the time domain data input from the IDFT processing unit 250 (step S106). Then, the subcarrier shift unit 262 performs subcarrier shift processing on the time domain data in which the CP is inserted by the CP insertion unit 261 (step S107).

[DFT Processing Procedure by Transmission Processing Unit in Embodiment 2]
Next, the procedure of the DFT process performed by the transmission processing unit 200 according to the second embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating an example of a DFT processing procedure performed by the transmission processing unit 200 according to the second embodiment. Note that the processing procedure shown in FIG. 7 corresponds to the DFT processing in step S103 shown in FIG.

  As illustrated in FIG. 7, the DFT processing unit 220 stores the time domain data “x (n)” input from the transmission data generation unit 210 in the data storage memory 221 (step S <b> 201). Subsequently, the DFT operation unit 222 initializes a frequency domain sample number “k” indicating a sample point of the frequency domain signal after the Fourier transform processing to “0” (step S202). Subsequently, the DFT operation unit 222 initializes the time domain sample number “n” indicating the sample point of the time domain signal before the Fourier transform process to “0” (step S203).

  Subsequently, the DFT operation unit 222 reads data x (n) in the time domain from the data storage memory 221 (step S204). Subsequently, the selection control unit 280 selects the phase closest to the phase of the DFT twiddle factor specified by the combination of the frequency domain sample number “k” and the time domain sample number “n” from the IDFT twiddle factor storage unit 240. An IDFT twiddle factor having the following is selected (step S205).

  Subsequently, the selection control unit 280 determines whether or not to correct the IDFT twiddle factor by comparing the DFT twiddle factor used by the DFT operation unit 222 with the IDFT twiddle factor selected in step S205. (Step S206). Then, as a result of the comparison, if the DFT twiddle factor and the IDFT twiddle factor are the same value, the selection control unit 280 determines that the correction process for the IDFT twiddle factor is unnecessary (No in step S206). The process proceeds to step S211.

  On the other hand, as a result of the comparison, if the DFT twiddle factor and the IDFT twiddle factor are not the same value, the selection control unit 280 determines to perform correction processing on the IDFT twiddle factor (Yes in step S206), and step The process proceeds to S207. Specifically, the selection control unit 280 corresponds to the phase specifying information “m” specified by the combination of the frequency domain sample number “k” and the time domain sample number “n” from the minute twiddle factor storage unit 270. A minute rotation factor and a code pattern are selected (step S207).

  Subsequently, the selection control unit 280 determines whether or not to perform a code inversion process based on the selected code pattern (step S208). If the selection control unit 280 determines not to perform the sign inversion process (No at Step S208), the selection control unit 280 proceeds to the process procedure of Step S210 without performing the code determination process. At this time, the selection control unit 280 instructs the selector 272 to output the minute twiddle factor selected in step S207 to the complex multiplier 290.

  On the other hand, when it is determined that the sign inversion process is to be performed (Yes at Step S208), the selection control unit 280 performs a process of inverting the sign of the Q component of the minute twiddle factor selected at Step S207 (Step S209). At this time, the selection control unit 280 instructs the selector 272 to output to the complex multiplier 290 the minute twiddle factor that has undergone the sign inversion process.

  Subsequently, the complex multiplier 290 corrects the IDFT twiddle factor to the DFT twiddle factor by performing complex multiplication of the IDFT twiddle factor selected in step S205 and the minute twiddle factor input from the selector 272. (Step S210).

  Subsequently, the DFT operation unit 222 multiplies the data x (n) read in step S204 by the twiddle factor input from the complex multiplier 290 (step S211). Subsequently, the DFT operation unit 222 accumulates the multiplication results (step S212). Then, the DFT computing unit 222 adds “1” to the time domain sample number “n” (step S213). When “n” is smaller than the DFT size (Yes at Step S214), the DFT operation unit 222 repeatedly performs the processing procedure at Steps S204 to S213. That is, the DFT calculation unit 222 accumulates the multiplication results in step S211 for n = “0” to “N−1”.

  On the other hand, when “n” is equal to or larger than the DFT size (No in step S214), the DFT operation unit 222 stores X (k) as the operation result in the data storage memory 221 (step S215). Subsequently, the DFT operation unit 222 adds “1” to the frequency domain sample number “k” (step S216). When “k” is smaller than the DFT size (Yes at Step S217), the DFT operation unit 222 repeats the processing procedure at Steps S203 to S216. On the other hand, when “k” is equal to or larger than the DFT size (No at Step S217), the DFT operation unit 222 outputs the data of the inverse Fourier transform processing result to the subcarrier mapping unit 230 (Step S218).

[Effect of Example 2]
As described above, the wireless communication device 20 according to the second embodiment holds a common minute twiddle factor corresponding to a plurality of pieces of phase specifying information “m”. In addition, the wireless communication device 20 holds the IDFT twiddle factor used during the inverse Fourier transform process. Further, the wireless communication device 20 generates a DFT rotation factor by correcting the IDFT rotation factor using the minute rotation factor, and performs a Fourier transform process using the generated DFT rotation factor.

  Thereby, the radio | wireless communication apparatus 20 which concerns on Example 2 can perform a Fourier-transform process only by hold | maintaining the number of micro twiddle factors smaller than DFT size. That is, since the wireless communication apparatus 20 according to the second embodiment only needs to hold a small number of twiddle factors, the circuit scale can be reduced, and as a result, power consumption can be reduced.

  Here, the reduction amount of the twiddle factor will be specifically described. In general, a conventional wireless communication apparatus holds 1200 DFT twiddle factors in order to perform Fourier transform with “DFT size = 1200”. However, as in the example illustrated in FIG. 5, the wireless communication device 20 according to the second embodiment only holds 37 minute twiddle factors even when Fourier transform is performed with “DFT size = 1200”. Good. That is, the wireless communication device 20 holds 1163 fewer small twiddle factors than the conventional wireless communication device as a twiddle factor for “DFT size = 1200”.

  Further, the DFT size 1152 minute twiddle factor storage unit 271-2 holds four minute twiddle factors in order to enable Fourier transform processing based on “DFT size = 1152” or the like. In addition, the micro-rotation factor storage units 271-3 to 271-10 have 67, 121, 7, 112, 13, 13, and 1 respectively so that Fourier transform processing can be executed according to each DFT size. , 22 and 40 micro twiddle factors. That is, the micro twiddle factor storage unit 270 according to the second embodiment holds a total of 424 micro twiddle factors in order to enable execution of Fourier transform processing using 34 types of DFT sizes. As described above, the conventional wireless communication apparatus holds a total of 9264 DFT twiddle factors. Therefore, the wireless communication apparatus 20 according to the second embodiment holds 8840 fewer twiddle factors than the conventional wireless communication apparatus.

  In the second embodiment, an example in which the DFT twiddle factor is generated by correcting the IDFT twiddle factor with a small twiddle factor has been described. However, by correcting the IDFT twiddle factor, a twiddle factor that approximates the DFT twiddle factor used in the DFT processing may be generated. Thus, in a third embodiment, an example of a wireless communication apparatus that generates a twiddle factor that approximates a DFT twiddle factor used for DFT processing will be described.

[Configuration of Wireless Communication Device According to Third Embodiment]
First, the configuration of a wireless communication apparatus according to the third embodiment (hereinafter referred to as “wireless communication apparatus 30”) will be described. The configuration of the wireless communication device 30 according to the third embodiment is the same as the configuration of the wireless communication device 20 illustrated in FIG. However, the transmission processing unit included in the wireless communication device 30 according to the third embodiment performs processing different from the transmission processing unit 200 included in the wireless communication device 20. The transmission processing unit included in the wireless communication device 30 according to the third embodiment will be described below with reference to FIG.

  FIG. 8 is a block diagram illustrating a configuration example of a transmission processing unit according to the third embodiment. In the following description, parts having the same functions as the constituent parts shown in FIG. As illustrated in FIG. 8, the transmission processing unit 300 according to the third embodiment includes a transmission data generation unit 210, a DFT processing unit 220, a subcarrier mapping unit 230, an IDFT twiddle factor storage unit 240, and an IDFT processing unit 250. A CP insertion unit 261, a subcarrier shift unit 262, a minute twiddle factor storage unit 370, a selection control unit 380, and a complex multiplier 290.

  The minute twiddle factor storage unit 370 includes a selector 371. The selector 371 outputs either data “1” or a minute twiddle factor represented by the following equation (15) to the complex multiplier 290. The selector 371 determines which data is output in accordance with an instruction from a selection control unit 380 described later.

  That is, the minute twiddle factor storage unit 370 in Example 3 holds only one minute twiddle factor represented by the above formula (15). The micro twiddle factor represented by the above equation (15) corresponds to a half phase of the phase interval of the IDFT twiddle factor stored in the IDFT twiddle factor storage unit 240. That is, by correcting the IDFT twiddle factor stored in the IDFT twiddle factor storage unit 240 using the minute twiddle factor expressed by the above equation (15), the twiddle factor used for the DFT processing is set to 2π. It can be approximated by a 4096 division factor.

  The micro twiddle factor in Example 3 will be described with reference to FIG. FIG. 9 is a diagram for explaining a minute twiddle factor in the third embodiment. In the example shown in FIG. 9, it is assumed that the DFT twiddle factor used during the Fourier transform process is “X21”. Further, of the IDFT twiddle factors stored in the IDFT twiddle factor storage unit 240, the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor “X21” is “Y21”. Then, when the IDFT twiddle factor “Y21” is corrected using the minute twiddle factor expressed by the above equation (15), the twiddle factor “Z21” is generated. In the example shown in FIG. 9, the phase of the DFT twiddle factor “X21” is closer to the phase of the IDFT twiddle factor “Y21” than the phase of the twiddle factor “Z21”. In such a case, the DFT calculation unit 222 performs a Fourier transform process using the IDFT twiddle factor “Y21”.

  In the example shown in FIG. 9, the DFT twiddle factor used in the Fourier transform process is “X22”, and the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor “X22” is “Y22”. Suppose that Then, when the IDFT twiddle factor “Y22” is corrected using the minute twiddle factor expressed by the above equation (15), the twiddle factor “Z22” is generated. In the example illustrated in FIG. 9, the phase of the twiddle factor “Z22” is closer to the phase of the twiddle factor “X22” for DFT than the phase of the twiddle factor “Y22” for IDFT. In such a case, the DFT operation unit 222 performs a Fourier transform process using the twiddle factor “Z22”.

  When the Fourier transform process is performed by the DFT operation unit 222, the selection control unit 380 first has an IDFT having a phase closest to the phase of the DFT twiddle factor used in the Fourier transform process from the IDFT twiddle factor storage unit 240. Select the twiddle factor. Then, the selection control unit 380 instructs the IDFT twiddle factor storage unit 240 to output the selected IDFT twiddle factor to the complex multiplier 290.

  Subsequently, the selection control unit 380 determines whether or not to correct the IDFT twiddle factor selected above by the minute twiddle factor represented by the above equation (15). Specifically, the selection control unit 380 determines that the phase of the IDFT twiddle factor after correction is closer to the phase of the twiddle factor used in the DFT processing than the phase of the IDFT twiddle factor before correction. Is determined to perform correction processing. In such a case, the selection control unit 380 instructs the selector 371 to output the minute twiddle factor expressed by the above equation (15).

  On the other hand, when the phase of the IDFT twiddle factor before correction is closer to the phase of the twiddle factor used in the DFT processing than the phase of the IDFT twiddle factor after correction, the selection control unit 380 It is determined that correction processing is not performed. In such a case, the selection control unit 380 instructs the selector 371 to output data “1”.

[DFT Processing Procedure by Transmission Processing Unit in Embodiment 3]
Next, the procedure of the DFT process performed by the transmission processing unit 300 according to the third embodiment will be described with reference to FIG. FIG. 10 is a flowchart illustrating an example of a DFT processing procedure performed by the transmission processing unit 300 according to the third embodiment.

  Note that the processing procedure in steps S301 to S305 shown in FIG. 10 is the same as the processing procedure in steps S201 to S205 shown in FIG. Also, the processing procedure in steps S308 to S315 shown in FIG. 10 is the same as the processing procedure in steps S211 to S218 shown in FIG.

  As shown in FIG. 10, after selecting the IDFT twiddle factor having the phase closest to the phase of the DFT twiddle factor (step S305), the selection control unit 380 determines whether to correct the selected IDFT twiddle factor. Is determined (step S306).

  Then, when performing the correction process (Yes at Step S306), the selection control unit 380 instructs the selector 371 to output the minute twiddle factor expressed by the above equation (15). Thereby, the complex multiplier 290 corrects the IDFT twiddle factor by performing complex multiplication of the IDFT twiddle factor selected in step S305 and the minute twiddle factor input from the selector 371 (step S307). . Complex multiplier 290 then outputs the corrected twiddle factor to DFT operation unit 222.

  On the other hand, when the correction process is not performed (No at Step S306), the selection control unit 380 instructs the selector 371 to output data “1”. Thus, complex multiplier 290 outputs the IDFT twiddle factor selected in step S305 to DFT operation unit 222.

[Effect of Example 3]
As described above, the wireless communication device 30 according to the third embodiment holds one minute twiddle factor without holding the DFT twiddle factor. And the radio | wireless communication apparatus 30 produces | generates the rotation factor approximated to the rotation factor used at the time of a Fourier-transform process by correct | amending the rotation factor for IDFT using a micro rotation factor.

  Thereby, the radio | wireless communication apparatus 30 which concerns on Example 3 can perform a Fourier-transform process only by hold | maintaining one micro twiddle factor. That is, since the wireless communication device 30 according to the third embodiment only needs to hold one twiddle factor, the circuit scale can be reduced, and as a result, power consumption can be reduced.

  Here, the reduction amount of the twiddle factor will be specifically described. As described above, the conventional wireless communication apparatus holds a total of 9264 DFT twiddle factors. Therefore, the wireless communication device 30 according to the third embodiment holds 9263 fewer twiddle factors than the conventional wireless communication device.

  In the third embodiment, the example in which the wireless communication device 30 holds one minute twiddle factor has been described. However, the wireless communication device 30 may hold a plurality of minute twiddle factors smaller than the phase interval of the IDFT twiddle factors stored in the IDFT twiddle factor storage unit 240. For example, the wireless communication device 30 has a minute twiddle factor corresponding to the phase of “1/3” of the phase interval of the IDFT twiddle factor and a minute amount of “2/3” of the phase interval of the IDFT twiddle factor. A twiddle factor may be retained. In the case of such an example, the wireless communication device 30 can approximate the twiddle factor used for the DFT processing by a twiddle factor obtained by dividing 2π by 6144.

  The wireless communication device and the like disclosed in the present application may be implemented in various different forms other than the above-described embodiments. Thus, in the fourth embodiment, another embodiment of the wireless communication device disclosed in the present application will be described.

[Physical channel, etc.]
In the second and third embodiments, an example in which data transmission is performed using PUSCH has been described. However, the wireless communication device and the like disclosed in the present application can also be applied when data transmission is performed using a physical channel other than PUSCH. Further, the wireless communication device disclosed in the present application can also be applied during data reception. Specifically, the wireless communication device and the like disclosed in the present application can also be applied when performing Fourier transform processing and inverse Fourier transform processing when receiving data.

[Mobile communication system]
In the second and third embodiments, the mobile communication system whose communication standard is LTE has been described as an example. However, the wireless communication device disclosed in the present application is also applicable to a mobile communication system that employs a communication standard other than LTE. it can. For example, the wireless communication device disclosed in the present application can be applied to a mobile communication system that performs Fourier transform processing and inverse Fourier transform processing at the time of data transmission or data reception.

[Micro-rotation factor]
The wireless communication devices described in the first to third embodiments may hold only the IDFT twiddle factor and the minute twiddle factor corresponding only to the first quadrant in the IQ complex plane. This is because the wireless communication device corresponds to the second quadrant to the fourth quadrant by performing sign inversion or switching between the I component and the Q component for the twiddle factor corresponding to the first quadrant in the IQ complex plane. This is because the twiddle factor to be calculated can be calculated. In such a case, the wireless communication device only needs to hold ¼ or ８ of the number of twiddle factors or minute twiddle factors than the wireless communication devices described in the first to third embodiments. For this reason, the wireless communication apparatus can further reduce the circuit scale by holding only the IDFT twiddle factor and the minute twiddle factor corresponding to only the first quadrant in the IQ complex plane.

  The following supplementary notes are further disclosed with respect to the embodiments including the above examples.

(Supplementary Note 1) For each of a plurality of phases having a constant phase difference, a twiddle factor storage unit that stores a twiddle factor corresponding to the phase;
A micro-rotation factor corresponding to phase identification information that is a combination of a time-domain sample number for identifying a sample point of a time-domain signal and a frequency-domain sample number for identifying a sample point of a frequency-domain signal. A micro twiddle factor storage unit that stores a micro twiddle factor corresponding to a small phase for each of a plurality of pieces of phase specifying information;
When a time domain signal is input, for each phase identification information in the time domain signal, an acquisition unit that acquires from the twiddle factor storage unit a phase factor closest to the phase identified by the phase identification information;
A correction unit that acquires, for each phase identification information, a minute twiddle factor corresponding to the phase identification information from the minute twiddle factor storage unit, and corrects the twiddle factor obtained by the obtaining unit using the obtained minute twiddle factor. When,
A wireless communication apparatus comprising: a Fourier transform unit that performs a Fourier transform process on an input time domain signal using the twiddle factor corrected by the correction unit.

(Additional remark 2) The said micro twiddle factor memory | storage part is in the said twiddle factor memory | storage part nearest to the phase specified by this phase specific information as a common micro twiddle factor corresponding to said several phase specific information, and this phase Memorize a minute twiddle factor corresponding to the phase difference from the stored twiddle factor phase,
The correction unit acquires, for each phase specifying information, a micro twiddle factor corresponding to the phase specifying information from the micro twiddle factor storage unit, and the twiddle factor acquired by the acquiring unit using the acquired micro twiddle factor The wireless communication device according to appendix 1, wherein the wireless communication device is corrected.

(Additional remark 3) The said micro twiddle factor memory | storage part matches with several phase specific information, and further memorize | stores the code | symbol information which shows whether the said common micro twiddle factor is positive or negative,
The correction unit acquires, for each phase specifying information, a micro twiddle factor and sign information corresponding to the phase specifying information from the micro twiddle factor storage unit, and when the acquired code information indicates positive, When correcting the twiddle factor acquired by the acquisition unit using a twiddle factor and the acquired sign information indicates negative, the micro twiddle factor obtained by inverting the sign of the orthogonal component of the micro twiddle factor is used. The wireless communication apparatus according to appendix 1 or 2, wherein the twiddle factor acquired by the acquisition unit is corrected.

(Supplementary Note 4) The Fourier transform unit is such that the phase of the twiddle factor acquired by the acquisition unit is closer to the phase specified by the phase specifying information than the phase of the twiddle factor corrected by the correction unit. In some cases, the wireless communication apparatus according to appendix 1, wherein Fourier transform processing is performed using the twiddle factor acquired by the acquisition unit.

(Additional remark 5) The said twiddle factor memory | storage part memorize | stores the twiddle factor used at the time of an inverse Fourier transform process, The radio | wireless communication apparatus as described in any one of Additional remark 1-4 characterized by the above-mentioned.

(Additional remark 6) The said micro twiddle factor memory | storage part memorize | stores the common micro twiddle factor corresponding to several phase specific information for every DFT size used at the time of a Fourier-transform process, Any of the additional marks 1-5 characterized by the above-mentioned. A wireless communication device according to any one of the above.

(Supplementary note 7) When a time domain signal is input, a time domain sample number for identifying a sample point of the time domain signal and a frequency domain sample number for identifying a sample point of a frequency domain signal corresponding to the time domain signal For each of the phase identification information that is a combination of An acquisition step for acquiring a near phase twiddle factor;
For each phase specifying information, a micro twiddle factor corresponding to the phase specifying information is acquired from a micro twiddle factor storage unit storing a micro twiddle factor corresponding to a phase smaller than the phase difference for each of the plurality of phase specifying information. A correction step for correcting the twiddle factor obtained by the obtaining step using the obtained minute twiddle factor;
And a Fourier transform step of performing a Fourier transform process on the input time domain signal using the twiddle factor corrected by the correcting step.

DESCRIPTION OF SYMBOLS 1 Base station 10 Wireless communication apparatus 11 Rotation factor memory | storage part 12 Minute rotation factor memory | storage part 13 Acquisition part 14 Correction | amendment part 15 Fourier transform part 20 Wireless communication apparatus 21 Reception antenna 22 Transmission antenna 23 Radio | wireless part 24 Upper layer 25 Baseband process part 26 Reception processing unit 27 Decoding unit 28 Encoding unit 30 Wireless communication device 200, 300 Transmission processing unit 210 Transmission data generation unit 220 DFT processing unit 221 Data storage memory 222 DFT operation unit 230 Subcarrier mapping unit 240 IDFT twiddle factor storage unit 250 IDFT processing unit 251 Data storage memory 252 IDFT calculation unit 261 CP insertion unit 262 Subcarrier shift unit 270, 370 Micro twiddle factor storage unit 271 Micro twiddle factor storage unit 272, 371 Selector 280, 380 Selection control unit 2 0 complex multiplier

Claims (5)

For each of a plurality of phases having a constant phase difference, a twiddle factor storage unit that stores a twiddle factor corresponding to the phase;
A micro-rotation factor corresponding to phase identification information that is a combination of a time-domain sample number for identifying a sample point of a time-domain signal and a frequency-domain sample number for identifying a sample point of a frequency-domain signal. A micro twiddle factor storage unit that stores a micro twiddle factor corresponding to a small phase for each of a plurality of pieces of phase specifying information;
When a time domain signal is input, for each phase identification information in the time domain signal, an acquisition unit that acquires from the twiddle factor storage unit a phase factor closest to the phase identified by the phase identification information;
A correction unit that acquires, for each phase identification information, a minute twiddle factor corresponding to the phase identification information from the minute twiddle factor storage unit, and corrects the twiddle factor obtained by the obtaining unit using the obtained minute twiddle factor. When,
A wireless communication apparatus comprising: a Fourier transform unit that performs a Fourier transform process on an input time domain signal using the twiddle factor corrected by the correction unit. The minute twiddle factor storage unit is stored as a common minute twiddle factor corresponding to the plurality of phase specifying information in the phase specified by the phase specifying information and the twiddle factor storage unit closest to the phase. Memorize the micro twiddle factor corresponding to the phase difference from the phase of the twiddle factor,
The correction unit acquires, for each phase specifying information, a micro twiddle factor corresponding to the phase specifying information from the micro twiddle factor storage unit, and the twiddle factor acquired by the acquiring unit using the acquired micro twiddle factor The wireless communication apparatus according to claim 1, wherein: The minute twiddle factor storage unit further stores sign information indicating whether the common minute twiddle factor is positive or negative in association with a plurality of phase specifying information,
The correction unit acquires, for each phase specifying information, a micro twiddle factor and sign information corresponding to the phase specifying information from the micro twiddle factor storage unit, and when the acquired code information indicates positive, When correcting the twiddle factor acquired by the acquisition unit using a twiddle factor and the acquired sign information indicates negative, the micro twiddle factor obtained by inverting the sign of the orthogonal component of the micro twiddle factor is used. The wireless communication apparatus according to claim 1, wherein the twiddle factor acquired by the acquisition unit is corrected.   The Fourier transform unit, when the phase of the twiddle factor acquired by the acquisition unit is closer to the phase specified by the phase specification information than the phase of the twiddle factor corrected by the correction unit The wireless communication apparatus according to claim 1, wherein Fourier transform processing is performed using the twiddle factor acquired by the acquisition unit. When a time domain signal is input, a combination of a time domain sample number for identifying a sample point of the time domain signal and a frequency domain sample number for identifying a sample point of a frequency domain signal corresponding to the time domain signal Rotation of the phase closest to the phase specified by the phase specification information from the twiddle factor storage unit that stores the twiddle factor corresponding to the phase for each of a plurality of phases having a certain phase difference for each phase specification information An acquisition step of acquiring a factor;
For each phase specifying information, a micro twiddle factor corresponding to the phase specifying information is acquired from a micro twiddle factor storage unit storing a micro twiddle factor corresponding to a phase smaller than the phase difference for each of the plurality of phase specifying information. A correction step for correcting the twiddle factor obtained by the obtaining step using the obtained minute twiddle factor;
And a Fourier transform step of performing a Fourier transform process on the input time domain signal using the twiddle factor corrected by the correcting step.

Images