COMMUNICATION DEVICE AND METHOD

• US 20110122938A1
• Filed: 11/23/2010
• Published: 05/26/2011
• Est. Priority Date: 11/24/2009
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: KAMEYA, Jun
• Application Number:
  US12/952,388
• Publication Number:
  US 20110122938A1
• Time in Patent Office: Days
• US Class Current: 375/228
• CPC Class Codes: H04L 27/263 modification of IFFT/IDFT modulator for performance improvement

Abstract

A communication device including: mapping frequency domain signals including phase information onto, of a band of subcarriers for transmitting the frequency domain signals, a band in which a twiddle factor for shifting the band of the subcarriers to a specified band is an integer power of an imaginary unit; performing inverse fast fourier transform on the subcarriers on which the frequency domain signals are mapped, to transform the subcarriers into time domain signals; increasing the number of samples by up-sampling the time domain signals; and executing, when the twiddle factor is an integer power of the imaginary unit, interchange processing for interchanging a real number component and an imaginary number component of each of the samples up-sampled or sign-reversal processing for reversing a sign of the real number component or the imaginary number component to shift the band of the frequency-domain-mapped subcarriers to the specified band.

Claims

1. A communication device comprising:

a mapping unit to map frequency domain signals including phase information onto a band in which a twiddle factor for shifting the band to a specified band is an integer power of an imaginary unit, the band is one of bands of subcarriers for transmitting the frequency domain signals;

an inverse fast fourier transform unit to perform inverse fast fourier transform on the subcarriers on which the frequency domain signals are mapped by the mapping unit, to transform the subcarriers into time domain signals;

an expanding unit to increase the number of samples by up-samplings the time domain signals transformed by the inverse fast fourier transform unit; and

a shifting unit to execute, when the twiddle factor is an integer power of the imaginary unit, interchange processing for interchanging a real number component and an imaginary number component of each of the samples up-sampled by the expanding unit and/or sign-reversal processing for reversing a sign of the real number component or the imaginary number component to shift the band of the frequency-domain-mapped subcarriers to the specified band.

2. The communication device according to claim 1, wherein:

the mapping unit comprises a multiplication reduction table to store a subcarrier band in which a value of the twiddle factor is an integer power of the imaginary unit, the subcarrier band is one of the bands of subcarriers onto which the frequency domain signals are mappable; and

the mapping unit maps the frequency domain signals onto the band that is the subcarrier band stored in the multiplication reduction table.

3. The communication device according to claim 1, wherein, when the twiddle factor is other than an integer power of the imaginary unit, the shift unit determines a product of the twiddle factor and each of the samples up-sampled by the expanding unit,

and when the twiddle factor is an integer power of the imaginary unit, the shift unit executes the interchange processing and/or the sign-reversal processing to shift the band of the frequency-domain-signal-mapped subcarriers to the specified band.

4. The communication device according to claim 1, wherein when the twiddle factor is 1, the shift unit uses a value of each of the samples, up-sampled by the expanding unit, as a value of a sample resulting from shifting of the band of the frequency-domain-signal-mapped subcarriers to the specified band.;

when the twiddle factor is the imaginary unit, the shift unit performs the interchange processing and reverses the sign of the real number component resulting from the interchange processing to shift the band of the frequency-domain-signal-mapped subcarriers to the specified band;

when the twiddle factor is −

1, the shift unit performs the sign-reversal processing to shift the band of the frequency-domain-signal-mapped subcarriers to the specified band; and

when the twiddle factor is a negative imaginary unit, the shift unit performs the interchange processing and reverses the sign of the imaginary number component resulting from the interchange processing to shift the band of the frequency-domain-signal-mapped subcarriers to the specified band.

5. A communication method comprising:

mapping frequency domain signals including phase information onto a band in which a twiddle factor for shifting the band to a specified band is an integer power of an imaginary unit, the band is one of bands of subcarriers for transmitting the frequency domain signals;

performing inverse fast fourier transform on the subcarriers on which the frequency domain signals are mapped by the mapping, to transform the subcarriers into time domain signals;

increasing a number of samples by up-sampling the time domain signals transformed by the inverse fast fourier transforming; and

executing, when the twiddle factor is an integer power of the imaginary unit, interchange processing for interchanging a real number component and an imaginary number component of each of the samples up-sampled by the increasing or sign-reversal processing for reversing a sign of the real number component or the imaginary number component to shift the band of the frequency-domain-mapped subcarriers to the specified band.