JP2013121136A - Transmitter and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter capable of reducing power consumption in the transmission processing, by reducing the throughput of inverse Fourier transform processing by a novel method.SOLUTION: In a transmitter 10, a symmetry determination unit 12 determines whether or not two symbols corresponding to first data and second data mapped to two carriers existing at positions symmetrical with respect to the center carrier of a carrier group exist at positions symmetrical with respect to one of the I axis and Q axis in the constellation. When a determination is made in the symmetry determination unit 12 that two symbols exist at positions symmetrical with respect to one of the I axis and Q axis, a reverse Fourier transform unit 13 performs reverse Fourier transform processing only on one of the I component and Q component, for the first data and second data.

Description

  The present invention relates to a transmission apparatus and a program that transmit signals using multicarriers.

  Conventionally, mobile communication using a wireless communication device such as a mobile terminal device or a base station has been used. At present, for example, an OFDM (Orthogonal Frequency Division Multiplexing) method is sometimes used as a mobile communication method.

  A wireless communication device compliant with the OFDM scheme performs an inverse Fourier transform (IFT) process on a modulated signal or the like when generating an OFDM symbol of transmission data. In the inverse Fourier transform process, an enormous number of multiplications are executed, and the processing amount of the inverse Fourier transform process occupies a large proportion of the processing amount of the entire transmission process. As a result, the power consumption of the wireless communication device compliant with the OFDM scheme increases.

  As a method that can reduce the amount of calculation of the inverse Fourier transform process, an inverse fast Fourier transform (IFFT) has been conventionally used. In general, in an inverse discrete Fourier transform (IDFT), when an IDFT size is N, N square complex multiplication is performed. On the other hand, in IFFT, NlogN complex multiplication processes are performed. That is, by using IFFT in the OFDM symbol generation process, the amount of processing in the inverse Fourier transform process can be reduced.

JP 2008-52504 A

  However, in IFFT, the number of data to be processed is limited to a power of two. For this reason, a method that can reduce the processing amount of the inverse Fourier transform other than IFFT is also desired.

  The disclosed technology has been made in view of the above, and provides a transmission device and a program that can reduce power consumption in transmission processing by reducing the amount of inverse Fourier transform processing by a novel method. Objective.

  In one aspect, the transmitting apparatus disclosed in the present application is present at a position symmetrical to the center carrier of the carrier group and a mapping unit that maps transmission data to a carrier group including a center carrier in frequency. Whether or not two symbols corresponding to the first data and the second data mapped to the two carriers that exist are in a symmetric position with respect to one of the I axis and the Q axis in the constellation. A determination unit for determining the first data and the second data corresponding to the two symbols determined by the determination unit to be in a position symmetrical to one of the I axis and the Q axis; And an inverse Fourier transform unit that performs an inverse Fourier transform process on only one of the I component and the Q component.

  In one aspect, the program disclosed in the present application maps transmission data to a carrier group including a center carrier in frequency, and exists in a position symmetrical to the center carrier in the carrier group. When two symbols corresponding to the first data and the second data mapped to one carrier are present at positions symmetrical with respect to one of the I axis and the Q axis in the constellation, the first data and The computer is caused to execute a transmission process for performing the inverse Fourier transform process on only one of the I component and the Q component for the second data.

  According to one aspect of the transmission apparatus and program disclosed in the present application, it is possible to reduce power consumption in transmission processing by reducing the amount of inverse Fourier transform processing by a novel method.

FIG. 1 is a block diagram illustrating a configuration example of a transmission device 10 according to the first embodiment. FIG. 2 is a diagram for explaining the mapping method by the mapping unit in the first embodiment. FIG. 3 is a block diagram illustrating a configuration example of the inverse Fourier transform unit in the first embodiment. FIG. 4 is a block diagram illustrating an exemplary configuration of the receiving apparatus according to Embodiment 1. FIG. 5 is a flowchart for explaining the processing of the symmetry determining unit in the first embodiment. FIG. 6 is a diagram for explaining Q-axis symmetry. FIG. 7 is a diagram for explaining I-axis symmetry. FIG. 8 is a flowchart for explaining the processing of the inverse Fourier transform unit in the first embodiment. FIG. 9 is a block diagram illustrating a configuration example of a transmission apparatus according to the second embodiment. FIG. 10 is a block diagram illustrating a configuration example of a wireless communication apparatus according to the third embodiment. FIG. 11 is a block diagram illustrating a configuration example of a transmission processing unit in the third embodiment. FIG. 12 is a flowchart illustrating a transmission processing procedure by the transmission processing unit according to the third embodiment. FIG. 13 is a flowchart illustrating an example of a switching process procedure by the control unit according to the third embodiment.

  Hereinafter, embodiments of a transmission device disclosed in the present application will be described in detail with reference to the drawings. In addition, the transmission apparatus and program which this application discloses are not limited by this embodiment. Moreover, the same code | symbol is attached | subjected to the structure which has the same function in embodiment, and the overlapping description is abbreviate | omitted.

[Embodiment 1]
[Configuration of Transmitting Device 10]
FIG. 1 is a block diagram illustrating a configuration example of a transmission device 10 according to the first embodiment. The transmission device 10 is a multicarrier transmission device that transmits signals using a plurality of carriers, and is, for example, an OFDM transmission device. In FIG. 1, the transmission device 10 includes a mapping unit 11, a symmetry determination unit 12, and an inverse Fourier transform unit 13.

  The mapping unit 11 maps input data (that is, transmission data) to a carrier group including a center carrier (hereinafter referred to as “center carrier”) in frequency. The input data of the mapping unit 11 is frequency domain data. The subcarrier group to which the input data is mapped is composed of, for example, a plurality of subcarriers that are continuous with the center carrier as the center and are as symmetrical as possible with the center carrier as the center. Specifically, as shown in FIG. 2, when transmitting transmission data using six subcarriers, the mapping unit 11 exists at a position symmetrical to the subcarrier 0 as the center carrier and the subcarrier 0. The transmission data is mapped to subcarriers ± 1 and subcarriers ± 2. Then, subcarrier-3 or subcarrier + 3 is selected as another subcarrier to which transmission data is mapped. FIG. 2 shows an example in which subcarrier-3 is selected.

  The transmission data mapped to the subcarrier group in this way is output to the symmetry determining unit 12 and the inverse Fourier transform unit 13.

  Here, the case where the subcarrier group to which the input data is mapped is composed of a plurality of subcarriers that are continuous with the center carrier as the center and that are as symmetrical as possible with the center carrier as the center has been described. However, the present invention is not limited to this, and the subcarrier group to which the input data is mapped may be composed of a plurality of subcarriers that exist in a jump. However, the subcarrier group to which the input data is mapped includes at least one set of two carriers existing at positions symmetrical to the center carrier.

  The symmetry determination unit 12 determines that two symbols corresponding to the first data and the second data mapped to two carriers existing in a symmetric position with respect to the center carrier in the carrier group are represented by I in the constellation. It is determined whether or not the axis exists symmetrically with respect to one of the axis and the Q axis. In the following description, two carriers that exist in symmetrical positions with respect to the center carrier and to which transmission data is mapped may be referred to as “carrier pairs”. The determination process by the symmetry determination unit 12 is performed for each carrier pair. Each of the first data and the second data described above corresponds to a “basic unit” to be described later.

  Then, the symmetry determination unit 12 generates a symmetry identification signal corresponding to the determination result and outputs it to the inverse Fourier transform unit 13.

  Specifically, the symmetry determination unit 12 identifies the I symmetry when two symbols corresponding to the first data and the second data mapped to the carrier pair exist at positions symmetrical with respect to the I axis. The signal is output to the inverse Fourier transform unit 13. Further, when two symbols corresponding to the first data and the second data mapped to the carrier pair are present at symmetrical positions with respect to the Q axis, a Q symmetry identification signal is output to the inverse Fourier transform unit 13. . In other cases, the symmetry determination unit 12 outputs an asymmetric identification signal to the inverse Fourier transform unit 13.

  The inverse Fourier transform unit 13 applies the first data and the second data corresponding to the carrier pair determined by the symmetry determination unit 12 to be in a symmetric position with respect to one of the I axis and the Q axis. The inverse Fourier transform process is performed only for one of the I component and the Q component. A signal obtained in the inverse Fourier transform process is a time domain signal.

  Specifically, the inverse Fourier transform unit 13 performs an inverse Fourier transform process according to the symmetry identification signal received from the symmetry determination unit 12. That is, when the inverse Fourier transform unit 13 receives the I-symmetric identification signal, the inverse Fourier transform 13 performs inverse Fourier transform only on the I component with respect to the first data and the second data. Further, when the inverse Fourier transform unit 13 receives the Q symmetry identification signal, the inverse Fourier transform is performed only on the Q component with respect to the first data and the second data. Further, when receiving the asymmetric identification signal, the inverse Fourier transform unit 13 performs an inverse Fourier transform process on both the I component and the Q component as usual for the first data and the second data.

  FIG. 3 is a block diagram illustrating a configuration example of the inverse Fourier transform unit 13. In FIG. 3, the inverse Fourier transform unit 13 includes an input memory 21, a twiddle factor storage unit 22, multipliers 23, 24, 25, and 26, adders 27 and 28, accumulators 29 and 30, and an output memory. 31 and a conversion control unit 32.

  The input memory 21 inputs an amount of data corresponding to the inverse Fourier transform processing size as one unit. That is, when the processing size of the inverse Fourier transform unit 13 is N (N is a natural number of 2 or more) subcarriers, one unit of data input to the input memory 21 includes N subcarriers. Corresponding N basic units are included.

  Then, the input memory 21 outputs the basic unit corresponding to the read address received from the conversion control unit 32 to the multipliers 23, 24, 25, and 26. The input memory 21 outputs the I component of the basic unit to the multiplier 23 and the multiplier 24. Further, the input memory 21 outputs the Q component of the basic unit to the multiplier 25 and the multiplier 26.

  The twiddle factor storage unit 22 holds a plurality of twiddle factors. The plurality of twiddle factors correspond to the sample points of the time domain signal that is finally output from the inverse Fourier transform unit 13.

  The twiddle factor storage unit 22 outputs the twiddle factor corresponding to the twiddle factor address received from the conversion control unit 32 to the multipliers 23, 24, 25, and 26. The twiddle factor storage unit 22 outputs the Q component of the twiddle factor to the multiplier 24 and the multiplier 25. The twiddle factor storage unit 22 outputs the I component of the twiddle factor to the multiplier 23 and the multiplier 26.

  Here, all of the N basic units are output from the input memory 21 for one twiddle factor output from the twiddle factor storage unit 22. Thereby, the multipliers 23, 24, 25, and 26 can obtain the multiplication result of the twiddle factor and the basic unit for all combinations of one twiddle factor and N basic units.

  Multiplier 23 multiplies the I component of the basic unit and the I component of the twiddle factor, and outputs the multiplication result to adder 27. The multiplier 23 operates and stops based on the clock 1 output from the conversion control unit 32. Similarly, the multiplier 24 multiplies the I component of the basic unit and the Q component of the twiddle factor, and outputs the multiplication result to the adder 28. The multiplier 24 is activated and deactivated based on the clock 2. The multiplier 25 multiplies the Q component of the basic unit and the Q component of the twiddle factor, and outputs the multiplication result to the adder 27. The multiplier 25 operates and stops based on the clock 1. Multiplier 26 multiplies the Q component of the basic unit and the I component of the twiddle factor, and outputs the multiplication result to adder 28. The multiplier 26 operates and stops based on the clock 2.

  The adder 27 calculates a difference between the multiplication result obtained by the multiplier 23 and the multiplication result obtained by the multiplier 25. The adder 27 operates and stops based on the clock 1. Here, the two multiplication results for which the difference is calculated share the same twiddle factor. Then, the calculation result in the adder 27 is output to the integrator 29. Similarly, the adder 28 calculates the sum of the multiplication result obtained by the multiplier 24 and the multiplication result obtained by the multiplier 26. The adder 28 operates and stops based on the clock 2.

  The accumulator 29 accumulates a plurality of calculation results received from the adder 27. The accumulator 29 operates and stops based on the clock 1. The integration process in the integrator 29 is performed with a calculation result corresponding to all combinations of one twiddle factor and N basic units as one unit. The integrator 29 outputs the integration result to the output memory 31 when the integration for this one unit is completed. The integration result in the integrator 29 corresponds to the I component of one sample point in the time domain signal. Similarly, the integrator 30 integrates a plurality of calculation results received from the adder 28. The accumulator 30 operates and stops based on the clock 2. The integration process in the integrator 30 is also performed with a calculation result corresponding to all combinations of one twiddle factor and N basic units as one unit. The integration result in the integrator 30 corresponds to the Q component of one sample point in the time domain signal.

  Here, the “I component system” includes multipliers 23 and 25, an adder 27, and an accumulator 29, and the “Q component system” includes multipliers 24 and 26, an adder 28, and an accumulator. 30.

  The output memory 31 outputs the integration results corresponding to all combinations of all of the twiddle factors and N basic units as one unit. That is, the data output as one unit from the output memory 31 includes a data unit corresponding to each sample point (hereinafter sometimes referred to as “sample unit”).

  The output memory 31 outputs the sample unit corresponding to the read address received from the conversion control unit 32 to the subsequent processing unit.

  The conversion control unit 32 outputs to the input memory 21 a read address corresponding to the basic unit to be output from the input memory 21. The basic unit to be output is sequentially changed. Further, the conversion control unit 32 outputs an address corresponding to the twiddle factor to be output from the twiddle factor storage unit 22 to the twiddle factor storage unit 22. The twiddle factor that is the output target is sequentially changed. Here, the conversion control unit 32 outputs the read address to the input memory 21 so that all the basic units are sequentially output for one twiddle factor. That is, the conversion control unit 32 sequentially outputs read addresses corresponding to all the basic units between a certain switching timing of the twiddle factor and the next switching timing.

  Further, the conversion control unit 32 outputs a clock signal corresponding to the symmetry identification signal received from the symmetry determination unit 12 to the I component system and the Q component system. Specifically, when receiving the I symmetry identification signal from the symmetry determining unit 12, the conversion control unit 32 turns on the clock signal (that is, clock 1) output to the I component system, while the Q component system The clock signal (that is, clock 2) output to is turned off. In addition, when receiving the Q symmetry identification signal from the symmetry determining unit 12, the conversion control unit 32 turns on the clock 2 and turns off the clock 1. In addition, when the conversion control unit 32 receives the asymmetric identification signal from the symmetry determination unit 12, both the clock 1 and the clock 2 are turned on.

  Further, the conversion control unit 32 outputs a read address corresponding to the sample unit to be output from the output memory 31 to the output memory 31.

[Configuration of Receiving Device 40]
FIG. 4 is a block diagram illustrating a configuration example of the receiving device 40 according to the first embodiment. The receiving device 40 is a multicarrier receiving device that receives signals using a plurality of carriers, and is, for example, an OFDM receiving device. In FIG. 4, the receiving device 40 includes a Fourier transform unit 41 and a demapping unit 42.

  The Fourier transform unit 41 converts the received signal in the time domain received from the transmission apparatus 10 into a frequency domain signal by performing a Fourier transform process. The received signal in the frequency domain corresponds to the output signal of the mapping unit 11 in the transmission device 10.

  The demapping unit 42 extracts a basic unit mapped to a subcarrier to be extracted and outputs the basic unit to a subsequent processing unit (for example, a decoding unit). This output signal corresponds to the input signal of the mapping unit 11 in the transmission device 10.

[Operation of Transmitting Device 10]
The operation of the transmission apparatus 10 having the above configuration will be described. FIG. 5 is a flowchart for explaining the processing of the symmetry determining unit 12. FIG. 6 is a diagram for explaining Q-axis symmetry. FIG. 7 is a diagram for explaining I-axis symmetry. FIG. 8 is a flowchart for explaining the processing of the inverse Fourier transform unit 13.

<Processing of Symmetry Determination Unit 12>
In step S101, the symmetry determining unit 12 sets zero as the value of k.

  In step S102, the symmetry determination unit 12 determines whether there is a carrier that is a subcarrier pair in the subcarrier k to which the basic unit X (k) is mapped. Here, since the subcarrier to be determined is the central carrier, there is always no carrier to be a subcarrier pair. Therefore, the determination in step S102 is negative. As a result, in step S107, the symmetry determining unit 12 generates an asymmetric identification signal.

  In step S108, the symmetry determining unit 12 increments the value of k.

  In step S109, the symmetry determining unit 12 determines whether or not the value of k has reached N. When it is determined in step S109 that N has not been reached, the symmetry determination unit 12 performs the determination process in step S102.

  If it is determined in step S102 that there is a subcarrier pair, in step S103, the symmetry determining unit 12 first and second data (data 1) and data (data 2) mapped to the subcarrier pair. It is determined whether or not the two symbols corresponding to () exist at positions symmetrical with respect to one of the I axis and the Q axis. That is, in step S103, it is determined whether or not one of the symmetry with respect to the I axis and the symmetry with respect to the Q axis exists.

  When it is determined in step S103 that one of the symmetry with respect to the I axis and the symmetry with respect to the Q axis exists, in step S104, the symmetry determination unit 12 determines whether or not there is symmetry with respect to the Q axis. . Note that if both the symmetry with respect to the I axis and the symmetry with respect to the Q axis do not exist in step S103, the symmetry determining unit 12 generates an asymmetric identification signal in step S107.

  If it is determined in step S104 that there is symmetry with respect to the Q axis, in step S105, the symmetry determination unit 12 generates a Q symmetry identification signal. If it is determined in step S104 that there is no symmetry with respect to the Q axis, the symmetry determination unit 12 generates an I symmetry identification signal in step S106.

  The above process is repeated until it is determined in step S109 that the value of k has reached N.

  When it is determined in step S109 that the value of k has reached N, in step S110, the symmetry determination unit 12 converts the symmetry identification signal generated in steps S105, S106, and S107 into an inverse Fourier transform unit. 13 to output.

  Next, the processing of the symmetry determination unit 12 will be specifically described using the mapping example shown in FIG. Here, description will be made assuming that the following data (that is, basic units) is mapped to subcarrier-3 to subcarrier 2 in FIG. That is, the data mapped to subcarrier-3 is exp (j3π / 8), the data of subcarrier-2 is exp (jπ / 8), and the data of subcarrier-1 is exp (jπ / 8). It is. The data mapped to subcarrier 0 is exp (j3π / 8), the data of subcarrier 1 is exp (j7π / 8), and the data of subcarrier 2 is exp (j3π / 8).

  In this case, in step S102, it is determined that subcarrier-2 and subcarrier2 and subcarrier-1 and subcarrier1 are subcarrier pairs, respectively.

  When attention is paid to the subcarrier pair of subcarrier-2 and subcarrier 2, two symbols corresponding to the data mapped to the subcarrier pair are positioned symmetrically with respect to the Q axis as shown in FIG. Exists. Therefore, for this subcarrier pair, a Q-symmetric identification signal is generated in step S105.

  When attention is paid to the subcarrier pair of subcarrier-1 and subcarrier 1, the two symbols corresponding to the data mapped to the subcarrier pair are positioned symmetrically with respect to the I axis as shown in FIG. Exists. Therefore, for this subcarrier pair, an I-symmetric identification signal is generated in step S106.

<Processing of Inverse Fourier Transform Unit 13>
In step S201, the input memory 21 stores input data. This input data is input with an amount corresponding to the processing size of the inverse Fourier transform as one unit.

  In step S202, the conversion control unit 32 sets zero as the value of n.

  In step S203, the conversion control unit 32 sets zero as the value of k.

  In step S204, the conversion control unit 32 causes the input memory 21 to read and output the basic unit X (k).

  In step S205, the conversion control unit 32 causes the twiddle factor storage unit 22 to read and output the twiddle factor exp (j2πnk / N).

  In step S206, the conversion control unit 32 determines the type of symmetry identification signal for the basic unit X (k).

  If it is determined in step S206 that the signal is an I-symmetric identification signal, in step S207, the conversion control unit 32 turns on the clock 1 and turns off the clock 2. As a result, since the Q component system is turned OFF, only the I component is calculated in step S208.

  If it is determined in step S206 that the signal is a Q-symmetric identification signal, in step S209, the conversion control unit 32 turns off the clock 1 and turns on the clock 2. As a result, since the I component system is turned OFF, only the Q component is calculated in step S210.

  If it is determined in step S206 that the signal is an asymmetric identification signal, in step S211, the conversion control unit 32 turns on both clock 1 and clock 2. As a result, in step S212, calculation is performed for both the I component and the Q component.

  As described above, when there is symmetry with respect to the I axis, the calculation for the Q component is stopped, and when there is symmetry with respect to the Q axis, the calculation for the I component is stopped. Thereby, the processing amount of inverse Fourier transform can be reduced.

  In step S 213, the integrator 29 integrates the calculation results received from the adder 27, and the integrator 30 integrates the plurality of calculation results received from the adder 28.

  In step S214, the conversion control unit 32 increments the value of k.

  In step S215, the conversion control unit 32 determines whether the value of k has reached N. If it is determined in step S215 that N has not been reached, the conversion control unit 32 performs the process of step S203. Thereby, the process of step S203-step S214 is repeated until it determines with having reached N in step S215. By this iterative process, the calculation for one sample point is performed.

  If it is determined in step S215 that N has been reached, in step S216, the conversion control unit 32 causes the integrators 29 and 30 to output the integration result X (n) for one sample point n, and causes the output memory 31 to Store.

  In step S217, the conversion control unit 32 causes the integrators 29 and 30 to clear the integration result.

  In step S218, the conversion control unit 32 increments the value of n.

  In step S219, the conversion control unit 32 determines whether the value of n has reached N.

  When it is determined in step S219 that N has not been reached, the conversion control unit 32 performs the process of step S204. Thereby, the process of step S204-step S218 is repeated until it determines with having reached N in step S219. By this iterative process, calculations are performed for all sample points.

  If it is determined in step S219 that N has been reached, the conversion control unit 32 causes the output memory 31 to output integration results for all sample points (that is, all sample units).

  Next, the process of the inverse Fourier transform unit 13 will be specifically described using the mapping example illustrated in FIG. Here, the data mapped to subcarrier-3 to subcarrier 2 is the same as that used in the description of symmetry determination unit 12 described above.

  First, the inverse Fourier transform is expressed by the following equation (1).

  In the above equation (1), x (n) represents time domain data after inverse Fourier transform. X (k) indicates frequency domain data before inverse Fourier transform. N indicates the IDFT size. N corresponds to the sample number of the time domain signal and takes a value of “0” to “N−1”. K corresponds to the subcarrier number and takes a value of “0” to “N−1”.

  Here, when attention is paid to the subcarrier pair of subcarrier-2 and subcarrier2, Q-axis symmetry exists. Therefore, the I component cancels out between the term exp (jπ / 8) exp (−j2πn × 2/2048) and the term exp (j3π / 8) exp (j2πn × 2/2048). Therefore, when Q-axis symmetry exists, it is sufficient to calculate only the Q component.

  When attention is paid to the subcarrier pair of subcarrier-1 and subcarrier1, I-axis symmetry exists. For this reason, the Q component cancels out between the term exp (jπ / 8) exp (−j2πn × 1/2048) and the term exp (j7π / 8) exp (j2πn × 1/2048). Therefore, when I-axis symmetry exists, it is sufficient to perform calculation only for the I component.

  Therefore, the inverse Fourier transform unit 13 calculates the IQ components of subcarrier-3 and subcarrier 0, calculates only the Q component of subcarrier-2 and subcarrier 2, and subcarrier-1 and I of subcarrier 1. Perform component-only operations.

By performing the calculation considering such IQ symmetry, the total calculation amount in the inverse Fourier transform unit 13 is as follows.
Number of multiplications: (4 × 2 + 2 × 4) × 2048 = 32768 times Number of integrations: (3 + 3) × 2048 = 12288 times

On the other hand, when IQ symmetry is not taken into consideration, the total calculation amount in the inverse Fourier transform process is as follows.
Number of multiplications: 4 × 6 × 2048 = 49152 times Number of integrations: (5 + 5) × 2048 = 20480 times

  In this way, by considering IQ symmetry, the number of multiplications can be reduced to 2/3 and the number of additions can be reduced to 3/5, compared with the case where IQ symmetry is not taken into consideration.

[Effect of Embodiment 1]
As described above, according to the present embodiment, in the transmission apparatus 10, the inverse Fourier transform unit 13 includes the first data and the second data mapped to the two carriers existing at positions symmetrical to the center carrier. When two symbols corresponding to the data are present at positions symmetrical with respect to one of the I axis and the Q axis, the inverse Fourier only for one of the I component and the Q component with respect to the first data and the second data. Perform the conversion process.

  Thereby, the processing amount of an inverse Fourier transform process can be reduced. Since the processing amount of the inverse Fourier transform process accounts for a large proportion of the processing amount of the entire transmission process, the consumption of the transmitting apparatus 10 in the transmission process is reduced by reducing the processing amount of the inverse Fourier transform process. Power can be reduced efficiently.

[Embodiment 2]
In the transmission apparatus according to the second embodiment, a carrier group to which transmission data is mapped by the mapping unit (hereinafter sometimes referred to as “temporary carrier group”) and a carrier group to which transmission data is actually transmitted (hereinafter referred to as “temporary carrier group”) Then, a shift process for shifting the temporary carrier group to the used carrier group is performed. In other words, in the transmission apparatus according to Embodiment 2, transmission data is mapped to a temporary carrier group including a center carrier, and the inverse of the IQ symmetry is taken into account, regardless of which carrier group is used. A Fourier transform process is performed. And the shift process from a temporary carrier group to a use carrier group is performed with respect to the signal of the time domain after an inverse Fourier transform.

[Configuration of Transmitter 50]
FIG. 9 is a block diagram illustrating a configuration example of the transmission device 50 according to the second embodiment. The transmission device 50 is a multicarrier transmission device that transmits signals using a plurality of carriers, and is, for example, an OFDM transmission device. In FIG. 9, the transmission device 50 includes a shift unit 51.

  The shift unit 51 receives the time-domain signal obtained by the inverse Fourier transform unit 13 and used carrier information from an upper layer (not shown). Then, when the temporary carrier group and the used carrier group indicated by the used carrier information are different, the shift unit 51 multiplies the time domain signal received from the inverse Fourier transform unit 13 by the twiddle factor. Thereby, the phase rotation process which shifts a temporary carrier group to a use carrier group is performed with respect to the signal of a time domain.

  Although an example in which used carrier information is input to the shift unit 51 is shown here, the present invention is not limited to this. For example, the shift unit 51 receives information on a twiddle factor calculated by another processing unit (for example, the mapping unit 11 or a higher layer) for shifting the temporary carrier group to the used carrier group, and based on the information. Shift processing may be performed.

[Effect of Embodiment 2]
As described above, according to the second embodiment, in the transmission device 50, the shift unit 51 multiplies the transmission signal in the time domain generated by the inverse Fourier transform unit 13 by the twiddle factor. The temporary carrier group is shifted to the used carrier group.

  Thereby, the signal obtained in the inverse Fourier transform process can be transmitted using the used carrier group. For this reason, even if the temporary carrier group and the used carrier group are different, the inverse Fourier transform process using IQ symmetry can be executed in the inverse Fourier transform unit 13 using the temporary carrier group. The amount can be reduced.

[Embodiment 3]
In the third embodiment, the transmission apparatus according to the first embodiment will be described using a specific example. In Embodiment 3, an example will be described in which the transmission apparatus described in Embodiment 1 is applied to a mobile communication system whose communication standard is LTE.

[Configuration of Radio Communication Device According to Embodiment 3]
FIG. 10 is a block diagram illustrating a configuration example of the wireless communication device 60 according to the third embodiment. The wireless communication device 60 is, for example, a portable terminal device that conforms to the LTE standard, and performs wireless communication with the base station 70. In FIG. 10, the wireless communication device 60 includes a reception antenna 61, a transmission antenna 62, a wireless unit 63, an upper layer 64, and a baseband processing unit 65.

  The receiving antenna 61 is an antenna that receives a signal from the outside. For example, the receiving antenna 61 receives a signal transmitted from the base station 70. The transmission antenna 62 is an antenna that transmits a signal to the outside. For example, the transmission antenna 62 transmits a signal to the base station 70. Note that the wireless communication device 60 may include a transmission / reception antenna that shares a reception antenna and a transmission antenna.

  The radio unit 63 transmits and receives radio signals via the reception antenna 61 and the transmission antenna 62. For example, the radio unit 63 performs radio processing such as A / D (Analog / Digital) conversion on the signal received from the receiving antenna 61. Further, for example, the radio unit 63 performs radio processing such as D / A (Digital / Analog) conversion on a signal input from the transmission processing unit 80 described later, and transmits the signal after the radio processing to the transmission antenna 62. To the base station 70.

  The upper layer 64 performs various processes based on the received data when the received received data is input from the decoding unit 67 described later. For example, when the received data is mail data, the upper layer 64 stores the received data in a predetermined storage area.

  Further, when transmitting data to the outside such as the base station 70, the upper layer 64 generates transmission data and outputs the generated transmission data to the encoding unit 68. For example, it is assumed that the wireless communication device 60 transmits data using a physical channel such as PUCCH (Physical Uplink Control Channel) or PUSCH (Physical Uplink Shared Channel). In such a case, the upper layer 64 generates transmission data based on, for example, a user operation. Further, for example, it is assumed that the wireless communication device 60 transmits data using a physical channel such as SRS (Sounding Reference Signal), DRS (Demodulation Reference Signal), or PRACH (Physical Random Access Channel). In such a case, the upper layer 64 outputs, for example, a Zadoff-Chu sequence number to the transmission processing unit 80.

  The baseband processing unit 65 performs baseband processing on transmission data and reception data. As illustrated in FIG. 10, the baseband processing unit 65 includes a reception processing unit 66, a decoding unit 67, an encoding unit 68, and a transmission processing unit 80.

  The reception processing unit 66 performs various reception processes on the reception data input from the wireless unit 63. For example, the reception processing unit 66 performs CP (Cyclic Prefix) deletion processing, demodulation processing, and the like on the reception data input from the wireless unit 63. The decoding unit 67 decodes the reception data input from the reception processing unit 66.

  The encoding unit 68 adds an error correction code to the transmission data input from the upper layer 64.

  The transmission processing unit 80 is configured to include the function of the transmission device 10 according to the first embodiment. The transmission processing unit 80 performs various transmission processes on the transmission data to which the error correction code is given by the encoding unit 68.

  FIG. 11 is a block diagram illustrating a configuration example of the transmission processing unit 80. In FIG. 11, the transmission processing unit 80 includes a transmission data generation unit 81, a DFT (Discrete Fourier Transform) unit 82, a mapping unit 83, selectors 84 and 85, an IFFT unit 86, a CP insertion unit 87, and a shift. Unit 88 and control unit 89.

  When the data bit sequence is input from the encoding unit 68, the transmission data generation unit 81 modulates the data bit sequence to generate transmission data. For example, the transmission data generation unit 81 modulates the data bit sequence by a modulation scheme such as BPSK (Binary Phase Shift Keying) or QPSK (Quadrature Phase Shift Keying). Further, when a Zadoff-Chu sequence number is designated from the upper layer 64, the transmission data generation unit 81 generates a Zadoff-Chu sequence based on the Zadoff-Chu sequence number.

  In addition, when modulating the data transmitted on the PUCCH, the transmission data generation unit 81 maps the data bit string input from the encoding unit 68 to a point on the circumference of the radius “1” on the IQ plane. The transmission data generation unit 81 also generates data corresponding to a point on the circumference having a radius “1” on the IQ plane even when generating data to be transmitted in SRS or DRS. That is, the amplitude of data transmitted in PUCCH, SRS, or DRS is “1” and is constant.

  Then, the transmission data generation unit 81 outputs the modulated or generated transmission data to the DFT unit 82 or to the mapping unit 11 and the mapping unit 83. For example, when the transmission data is data transmitted in PUCCH, SRS, or DRS, the transmission data generation unit 81 outputs the transmission data to the mapping unit 11 and the mapping unit 83. For example, when the transmission data is data transmitted on the PRACH or PUSCH, the transmission data generation unit 81 outputs the transmission data to the DFT unit 82.

  The DFT unit 82 converts the time domain data into frequency domain data by performing a Fourier transform process on the transmission data input from the transmission data generation unit 81. Then, the DFT unit 82 outputs the frequency domain data to the mapping unit 11 and the mapping unit 83. The mapping unit 83 maps the transmission data input from the transmission data generation unit 81 or the frequency domain data input from the DFT unit 82 to the used carrier group.

  The selector 84 outputs the transmission data mapped to the used carrier group by the mapping unit 83 to the IFFT unit 86 or the transmission data mapped to the temporary carrier group by the mapping unit 11 as the symmetry determining unit 12 and the inverse Fourier. The data is output to the conversion unit 13. Note that the selector 84 outputs the transmission data mapped to the used carrier group to the IFFT unit 86 or transmits the mapping mapped to the temporary carrier group according to a selection signal input from the switching control unit 90 described later. Whether to output the data to the symmetry determination unit 12 and the inverse Fourier transform unit 13 is determined.

  The IFFT unit 86 performs an inverse fast Fourier transform process having an IFFT size “N” using the transmission data mapped to the used carrier group by the mapping unit 84 and the twiddle factor. Accordingly, IFFT unit 86 converts transmission data mapped to the used carrier group by mapping unit 83 into time domain data.

  The IFFT unit 86 uses the transmission data mapped to the used carrier group by the mapping unit 83 and the twiddle factor stored in the twiddle factor storage unit (not shown), and the inverse high speed of IFFT size “N”. Perform Fourier transform processing. Accordingly, IFFT unit 86 converts transmission data mapped to the used carrier group by mapping unit 83 into time domain data. The twiddle factor storage unit (not shown) stores N twiddle factors that are IDFT sizes. For example, when the IDFT size is “2048”, the twiddle factor storage unit (not shown) stores 2048 twiddle factors obtained by dividing 2π by 2048.

  The selector 85 outputs the transmission data in the time domain after the inverse Fourier transform input from the IFFT unit 86 or the inverse Fourier transform unit 13 to the CP insertion unit 87. Note that the selector 85 determines whether to output the transmission data input from the IFFT unit 86 or the inverse Fourier transform unit 13 to the CP insertion unit 87 according to the selection signal input from the switching control unit 90.

  The CP insertion unit 87 sets a CP for a predetermined time at the end of the transmission data input from the selector 85, and inserts the CP at the beginning of the transmission data.

  The shift unit 88 performs frequency shift by multiplying the transmission data into which the CP is inserted by the CP insertion unit 87 by a twiddle factor. Specifically, when the CP is inserted into the time-domain transmission data after the inverse Fourier transform input from the IFFT unit 86 by the selector 85, the shift unit 88 sets “1/2” of the bandwidth of each subcarrier. Shift the frequency by that amount. On the other hand, when CP is inserted into the transmission data in the time domain after the inverse Fourier transform input from the inverse Fourier transform unit 13 by the selector 85, the shift unit 88 is “½” of the bandwidth of each subcarrier. In addition, the difference between the temporary carrier group and the used carrier group also shifts the frequency. In the following, a process of performing frequency shift by “½” of the bandwidth of each subcarrier is referred to as “½ subcarrier shift process”, and in addition to “½”, a provisional carrier group In some cases, the difference between the used carrier group and the used carrier group is expressed as “difference shift processing”.

  The control unit 89 controls the selectors 84 and 85, the IFFT unit 86, and the inverse Fourier transform unit 13. Specifically, as illustrated in FIG. 11, the control unit 89 includes a switching control unit 90 and a clock control unit 91.

  The switching control unit 90 selects either the IFFT unit 86 or the inverse Fourier transform unit 13 as a processing unit that performs inverse Fourier transform processing based on the amplitude of each transmission data mapped to the subcarrier and the number of used subcarriers. Switch to. Then, the switching control unit 90 outputs a selection signal indicating which processing unit of the IFFT unit 86 or the inverse Fourier transform unit 13 performs the inverse Fourier transform process to the selector 84 and the selector 85.

  The switching process by the switching control unit 90 will be specifically described. The switching control unit 90 determines whether or not the amplitude of each transmission data mapped to the subcarrier by the mapping unit 11 and the mapping unit 83 is constant. For example, the amplitude of data transmitted in PUCCH, SRS, or DRS is a constant value “1”. Therefore, the switching control unit 90 has a constant amplitude when the transmission data mapped to the subcarriers by the mapping unit 11 and the mapping unit 83 is data transmitted in PUCCH, SRS, or DRS, for example. Is determined.

When the switching control unit 90 determines that the amplitude of each transmission data mapped to the subcarrier is not constant, the switching control unit 90 controls the IFFT unit 86 to perform the inverse Fourier transform process. On the other hand, when the switching control unit 90 determines that the amplitude of each transmission data mapped to the subcarrier is constant, the switching control unit 90 determines whether the number of used subcarriers is smaller than a threshold T1 that is a predetermined threshold. To do. When the switching control unit 90 determines that the number of used subcarriers is equal to or greater than the threshold value T1, the switching control unit 90 performs control so that the inverse Fourier transform process is performed by the IFFT unit 86. On the other hand, when the number of used subcarriers is smaller than the threshold value T1, the switching control unit 90 controls the inverse Fourier transform unit 13 to perform the inverse Fourier transform process.

  For example, the switching control unit 90 controls the processing unit that performs the inverse Fourier transform process by outputting “0” or “1” as the selection signal to the selector 84 and the selector 85. Here, when the selection signal is “0”, it indicates that the IFFT unit 86 performs the inverse Fourier transform process, and when the selection signal is “1”, the inverse Fourier transform unit 13 performs the inverse process. It shall indicate that a Fourier transform process is performed. In such a case, when the selection signal “0” is input from the switching control unit 90, the selector 84 outputs the transmission data mapped to the subcarrier by the mapping unit 83 to the IFFT unit 86. Further, when the selection signal “1” is input from the switching control unit 90, the selector 84 outputs the transmission data mapped to the subcarrier by the mapping unit 11 to the inverse Fourier transform unit 13. Further, when the selection signal “0” is input from the switching control unit 90, the selector 85 outputs the transmission data input from the IFFT unit 86 to the CP insertion unit 87. Further, when the selection signal “1” is input from the switching control unit 90, the selector 85 outputs the transmission data input from the inverse Fourier transform unit 13 to the CP insertion unit 87.

  The clock control unit 91 activates the clock of the processing unit controlled to perform the inverse Fourier transform process by the switching control unit 90, and stops the clock of the processing unit controlled not to perform the inverse Fourier transform process. For example, it is assumed that the switching control unit 90 controls the IFFT unit 86 to perform an inverse Fourier transform process. In such a case, the clock control unit 91 activates the operation clock of the IFFT unit 86 and stops the operation clock of the inverse Fourier transform unit 13. For example, it is assumed that the switching control unit 90 performs control so that the inverse Fourier transform unit 13 performs the inverse Fourier transform process. In such a case, the clock control unit 91 activates the operation clock of the inverse Fourier transform unit 13 and stops the operation clock of the IFFT unit 86.

  Thus, the clock control unit 91 can prevent the power consumption from increasing by stopping the clock of the processing unit that does not perform the inverse Fourier transform process. For example, since the IFFT unit 86 is stopped when the inverse Fourier transform unit 13 performs the inverse Fourier transform process, the clock control unit 91 can reduce the power consumed by the IFFT unit 86.

  The transmission data generation unit 81, the DFT unit 82, the mapping units 11, 83, the IFFT unit 86, the symmetry determination unit 12, the inverse Fourier transform unit 13, the CP insertion unit 87, the shift unit 88, and the control unit 89 described above are: For example, an electronic circuit. 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).

  In the above description, the IFFT unit 86 and the inverse Fourier transform unit 13 each include a twiddle factor storage unit. However, the present invention is not limited to this, and a twiddle factor storage unit is provided as an independent component. Also good. In this case, the twiddle factor storage unit is, for example, a semiconductor memory device such as a random access memory (RAM), a read only memory (ROM), or a flash memory, or a storage device such as a hard disk or an optical disk.

[Operation of Wireless Communication Device 60 according to Embodiment 3]
The operation of the wireless communication device 60 having the above configuration will be described. FIG. 12 is a flowchart showing a transmission processing procedure by the transmission processing unit 80 in the third embodiment. FIG. 13 is a flowchart illustrating an example of a switching process procedure by the control unit 89 according to the third embodiment.

<Processing of Transmission Processing Unit 80>
First, the transmission processing procedure by the transmission processing unit 80 will be described. As illustrated in FIG. 12, when data transmission is performed by the wireless communication device 60 (Yes in step S301), the transmission data generation unit 81 performs transmission processing to generate transmission data by performing modulation processing or generating a Zadoff-Chu sequence. Is generated (step S302).

  When the transmission data generation unit 81 generates transmission data to be processed by DFT processing (Yes at step S303), the transmission data generation unit 81 outputs the generated transmission data to the DFT unit 82. On the other hand, when the transmission data generation unit 81 generates transmission data that is not subject to DFT processing (No in step S303), the transmission data generation unit 81 outputs the generated transmission data to the mapping unit 11 and the mapping unit 83. When the transmission data is input from the transmission data generation unit 81, the DFT unit 82 performs a Fourier transform process using the transmission data (step S304).

  Subsequently, in step S305, the mapping unit 11 maps the transmission data input from the transmission data generation unit 81 or the frequency domain data input from the DFT unit 82 to the temporary carrier group. The mapping unit 83 maps the transmission data input from the transmission data generation unit 81 or the frequency domain data input from the DFT unit 82 to the used carrier group.

  Subsequently, the control unit 89 performs switching processing for switching the processing unit that performs the inverse Fourier transform processing based on the amplitude of the transmission data mapped to each subcarrier by the mapping unit 83 and the number of subcarriers used (step) S306). The switching process by the control unit 89 will be described later with reference to FIG.

  When the processing unit that performs the inverse Fourier transform process is switched to the inverse Fourier transform unit 13 by the control unit 89 (Yes in step S307), the inverse Fourier transform unit 13 performs the inverse Fourier transform process (step S308).

  Subsequently, the CP insertion unit 87 inserts the CP into the time domain data input from the inverse Fourier transform unit 13 (step S309). Then, the shift unit 88 performs a difference shift process on the time domain data in which the CP is inserted by the CP insertion unit 87 (step S310).

  On the other hand, when the processing unit that performs the inverse Fourier transform process is switched to the IFFT unit 86 by the control unit 89 (No in step S307), the IFFT unit 86 performs the inverse fast Fourier transform process (step S311).

  Subsequently, the CP insertion unit 87 inserts the CP into the time domain data input from the IFFT unit 86 (step S312). Then, the shift unit 88 performs a ½ shift process on the time domain data in which the CP is inserted by the CP insertion unit 87 (step S313).

<Processing of control unit 89>
Next, the procedure of switching processing by the control unit 89 will be described.

  As illustrated in FIG. 13, the switching control unit 90 of the control unit 89 determines whether or not the amplitude of each transmission data mapped to the subcarrier by the mapping unit 83 is constant (step S401). Then, when the amplitude of each transmission data is constant (Yes at Step S401), the switching control unit 90 determines whether or not the number of used subcarriers is smaller than the threshold T1 (Step S402).

  When the switching control unit 90 determines that the number of used subcarriers is smaller than the threshold T1 (Yes at Step S402), the control unit 89 performs an inverse Fourier transform process by the inverse Fourier transform unit 13. To control.

  Specifically, the clock control unit 91 of the control unit 89 activates the operation clock of the inverse Fourier transform unit 13 (step S403) and stops the operation clock of the IFFT unit 86 (step S404). Then, the switching control unit 90 outputs a selection signal indicating that the inverse Fourier transform process is performed by the inverse Fourier transform unit 13 to the selector 84 and the selector 85 (step S405).

  On the other hand, when the switching control unit 90 determines that the amplitude of each transmission data is not constant (No at Step S401), the control unit 89 controls the IFFT unit 86 to perform the inverse Fourier transform process. Alternatively, when the switching control unit 90 determines that the number of used subcarriers is equal to or greater than the threshold T1 (No at Step S402), the control unit 89 performs control so that the IFFT unit 86 performs inverse Fourier transform processing. To do.

  Specifically, the clock control unit 91 activates the operation clock of the IFFT unit 86 (step S406) and stops the operation clock of the inverse Fourier transform unit 13 (step S407). Then, the switching control unit 90 outputs a selection signal indicating that the inverse Fourier transform process is performed by the IFFT unit 86 to the selector 84 and the selector 85 (step S408).

  Here, the effect when the inverse Fourier transform in consideration of the symmetry in the inverse Fourier transform unit 13 is applied to the data transmitted on the PUCCH will be described. The conditions for PUCCH transmission are as follows. According to the LTE standard, format 1a (b (0) = '0'), noc = 0, slot = 0, α = 0, u = 0. Further, the temporary carrier group is assumed to be the central 12 subcarriers.

In this case, the following data (that is, basic units) are mapped to subcarrier-6 to subcarrier 5. That is, the data mapped to subcarrier-6 is exp (j7π / 8), the data mapped to subcarrier-5 is exp (jπ / 8), and the data mapped to subcarrier-4 is exp (j3π / 8). The data mapped to subcarrier-3 is exp (j5π / 8), the data mapped to subcarrier-2 is exp (j3π / 8), and the data mapped to subcarrier-1 is exp (j3π / 8). The data mapped to subcarrier 0 is exp (jπ / 8), the data mapped to subcarrier 1 is exp (jπ / 8), and the data mapped to subcarrier 2 is exp (j3π). / 8). The data mapped to subcarrier 3 is exp (jπ / 8), the data mapped to subcarrier 4 is exp (j5π / 8), and the data mapped to subcarrier 5 is exp (j3π / 8).

  In this case, subcarrier-1 and subcarrier 1, subcarrier-4 and subcarrier 4, subcarrier-5 and subcarrier 5 are subcarrier pairs.

  When attention is paid to the subcarrier pair of subcarrier-1 and subcarrier 1, two symbols corresponding to data mapped to the subcarrier pair exist at positions symmetrical with respect to the Q axis. Therefore, for the subcarrier pair, the inverse Fourier transform unit 13 performs only the calculation for the Q component.

  When attention is paid to the subcarrier pair of subcarrier-4 and subcarrier 4, two symbols corresponding to the data mapped to the subcarrier pair exist at positions symmetrical with respect to the I axis. Therefore, for the subcarrier pair, the inverse Fourier transform unit 13 performs only the calculation for the I component.

  When attention is paid to the subcarrier pair of subcarrier-5 and subcarrier 5, two symbols corresponding to data mapped to the subcarrier pair exist at positions symmetrical with respect to the Q axis. Therefore, for the subcarrier pair, the inverse Fourier transform unit 13 performs only the calculation for the Q component.

By performing the calculation considering such IQ symmetry, the total calculation amount in the inverse Fourier transform unit 13 is as follows.
Number of multiplications: (4 × 6 + 2 × 6) × 2048 = 73728 times Number of integrations: (7 + 9) × 2048 = 32768 times

On the other hand, when IQ symmetry is not taken into consideration, the total calculation amount in the inverse Fourier transform process is as follows.
Number of multiplications: 4 × 12 × 2048 = 98304 times Number of integrations: (11 + 11) × 2048 = 45056 times

  In this way, by considering IQ symmetry, the number of multiplications can be reduced to 3/4 and the number of additions can be reduced to about 0.73 compared to the case where IQ symmetry is not considered.

[Effect of Embodiment 3]
As described above, according to the present embodiment, in radio communication apparatus 60, inverse Fourier transform unit 13 performs inverse Fourier transform processing only when the number of used carriers is smaller than threshold value T1, and IFFT unit 86 uses The inverse fast Fourier transform is performed only when the number of carriers is equal to or greater than the threshold value T1.

  Thereby, the radio | wireless communication apparatus 60 can perform an inverse Fourier transform with the processing amount smaller than an inverse fast Fourier transform, when the number of used subcarriers is smaller than threshold value T1. Therefore, the wireless communication device 60 can reduce the load applied to the inverse Fourier transform.

  Further, in the wireless communication device 60, the clock control unit 91 is controlled not to perform the inverse Fourier transform process by starting the clock of the processing unit controlled to perform the inverse Fourier transform process by the switching control unit 90. Stop the processing unit clock.

  Thereby, since the radio | wireless communication apparatus 60 stops the clock of the process part which does not perform an inverse Fourier transform process, it can prevent that power consumption increases.

[Wireless communication system]
In the above description, 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 can also be applied to a mobile communication system employing a communication standard other than LTE. Specifically, the wireless communication device disclosed in the present application can be applied to a mobile communication system that performs wireless communication using OFDM technology. For example, the wireless communication device disclosed in the present application can also be applied to a mobile communication system such as WiMAX (Worldwide Interoperability for Microwave Access).

DESCRIPTION OF SYMBOLS 10,50 Transmitter 11,83 Mapping part 12 Symmetry determination part 13 Inverse Fourier transform part 21 Input memory 22 Rotation factor memory | storage part 23,24,25,26 Multiplier 27,28 Adder 29,30 Accumulator 31 Output memory 32 conversion control unit 40 reception device 41 Fourier transform unit 42 demapping unit 51 shift unit 60 wireless communication device 61 reception antenna 62 transmission antenna 63 radio unit 64 upper layer 65 baseband processing unit 66 reception processing unit 67 decoding unit 68 encoding unit 70 base station 80 transmission processing unit 81 transmission data generation unit 82 DFT unit 84, 85 selector 86 IFFT unit 87 CP insertion unit 88 shift unit 89 control unit

Claims (4)

A mapping unit that maps transmission data to a carrier group including a center carrier in frequency;
In the constellation, two symbols corresponding to the first data and the second data mapped to two carriers existing in a symmetrical position with respect to the center carrier in the carrier group are the I axis and the Q axis. A determination unit for determining whether or not the object exists at a position symmetrical to one of
With respect to the first data and the second data corresponding to the two symbols determined to be present at a symmetrical position with respect to one of the I axis and the Q axis by the determination unit, an I component and a Q An inverse Fourier transform unit that performs an inverse Fourier transform process on only one of the components;
A transmission apparatus comprising: A shift unit that shifts the carrier group to a used carrier group that is actually used for transmission of the transmission data by multiplying a time domain transmission signal generated by the inverse Fourier transform process by a twiddle factor. ,
The transmission device according to claim 1, further comprising: A determination unit for determining whether the number of carriers constituting the carrier group is smaller than a predetermined threshold;
A second mapping unit that maps the transmission data to the used carrier group;
A second inverse Fourier transform unit that performs an inverse fast Fourier transform on the transmission data mapped by the second mapping unit;
Further comprising
The first inverse Fourier transform unit performs the inverse Fourier transform process only when the number of carriers is smaller than the threshold,
The second inverse Fourier transform unit performs the inverse fast Fourier transform only when the number of carriers is equal to or greater than the threshold value.
The transmission apparatus according to claim 1 or 2. Map the transmission data to the carrier group including the center carrier at the frequency,
In the constellation, two symbols corresponding to the first data and the second data mapped to two carriers existing in a symmetrical position with respect to the center carrier in the carrier group are the I axis and the Q axis. In the case where the first data and the second data are present at a position symmetric with respect to one of the two, an inverse Fourier transform process is performed on only one of the I component and the Q component.
A program that causes a computer to execute transmission processing.

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