METHOD AND APPARATUS FOR ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING COMMUNICATION

• US 20080112310A1
• Filed: 04/25/2007
• Published: 05/15/2008
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: OH, Ji-sung, CHOI, Pil-soon
• Granted Patent: US 8,170,064 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 27/0006 Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio for spectrum sharing between different networks H04W16/14
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

A method and apparatus for transmitting and receiving a digital signal using an orthogonal frequency division multiplexing (OFDM) communication system are provided. In this method, subcarriers are split into a plurality of subcarrier groups according to available frequency bandwidths and are respectively transmitted in a transmitting portion and the subcarrier groups are combined and are restored to the original signal in a receiving portion. Therefore, wireless resources may be used efficiently by combining with cognitive radio technology.

Claims

1. A method of transmitting a digital signal, the method comprising:

splitting the digital signal at baseband into a plurality of signals according to available frequency bands;

performing inverse fast Fourier transformation (IFFT) on each of the plurality of signals to generate subcarriers; and

transmitting the subcarriers through the available frequency bands.

2. The method of transmitting a digital signal of claim 1, the method further comprising searching for the available frequency bands using cognitive radio technology.

3. The method of transmitting a digital signal of claim 1,

wherein the plurality of signals comprises a plurality of subcarrier groups, and each of the subcarrier groups comprises at least one subcarrier,

wherein the IFFT is performed on each of the subcarrier groups, and

wherein the transmitting comprises:

low-pass-filtering each of the subcarrier groups;

modulating each of the low-pass-filtered subcarrier groups independently using different radio frequency (RF) signal; and

transmitting the modulated subcarrier groups.

4. The method of transmitting a digital signal of claim 3, wherein the modulating each of the low-pass-filtered subcarrier groups comprises frequency up-converting each of the low-pass-filtered subcarrier groups using the different RF signals.

5. The method of transmitting a digital signal of claim 3, wherein the low-pass-filtering is performed according to a bandwidth of each of the subcarrier groups.

6. The method of transmitting a digital signal of claim 3, wherein the different RF signals have different frequencies from each other, and are generated by at least one of a frequency divider and a frequency multiplier using a signal output from a phase-locked loop (PLL) circuit.

7. A computer readable recording medium having recorded thereon a computer program for executing a method of transmitting a digital signal, the method comprising:

splitting the digital signal at baseband into a plurality of signals according to available frequency bands;

performing inverse fast Fourier transformation (IFFT) on each of the plurality of signals to generate subcarriers; and

transmitting the subcarriers through the available frequency bands.

8. An apparatus for transmitting a digital signal, the apparatus comprising:

a splitter which splits the digital signal at baseband into a plurality of signals according to available frequency bands;

a plurality of inverse fast Fourier transformation (IFFT) units which performs IFFT on each of the plurality of signals to generate subcarriers; and

a transmitter which transmits the subcarriers through the available frequency bands.

9. The apparatus for transmitting a digital signal of claim 8, the apparatus further comprising a cognitive unit which searches for the available frequency bands using cognitive radio technology.

10. The apparatus for transmitting a digital signal of claim 8,

wherein the plurality of signals split according to the available frequency bands comprise a plurality of subcarrier groups, and each of the subcarrier groups comprises at least one subcarrier,

wherein the IFFT is performed on each of the subcarrier groups, and wherein the transmitter comprises:

a plurality of low-pass filters which low-pass-filters each of the subcarrier groups;

a plurality of mixers which modulates each of the low-pass-filtered subcarrier groups independently using different radio frequency (RF) signals; and

a plurality of RF transmitters which transmits the modulated subcarrier groups.

11. The apparatus for transmitting a digital signal of claim 10, wherein the mixers are configured to frequency up-convert each of the low-pass-filtered subcarrier groups using the different RF signals.

12. The apparatus for transmitting a digital signal of claim 10, wherein the low-pass filters low-pass-filter each of the subcarrier groups according to a bandwidth of each of the subcarrier groups.

13. The apparatus for transmitting a digital signal of claim 10, the apparatus further comprising:

a phase-locked loop (PLL) circuit which generates an RF signal; and

at least one of a frequency divider and a frequency multiplier which generates the different RF signals which have different frequencies from each other using the RF signal output from the PLL circuit,

wherein the mixers modulate the subcarrier groups using the different RF signals which have different frequencies from each other.

14. A method of receiving a digital signal, the method comprising:

receiving subcarrier groups modulated using radio frequency (RF) signals which have different frequencies from each other;

demodulating each of the subcarrier groups so that all subcarriers of each of the subcarrier groups are arranged adjacent to each other at baseband;

performing fast Fourier transformation (FFT) on each of the demodulated subcarrier groups independently; and

combining the subcarrier groups on which the FFT is performed.

15. The method of receiving a digital signal of claim 14, wherein the demodulating comprises:

frequency down-converting each of the subcarrier groups independently using the RF signals which have different frequencies from each other; and

low-pass-filtering each of the frequency down-converted subcarrier groups according to a bandwidth of each of the subcarrier groups.

16. The method of receiving a digital signal of claim 15, wherein the RF signals which have different frequencies from each other are generated by at least one of a frequency divider and a frequency multiplier using a signal output from a phase-locked loop (PLL) circuit.

17. A computer readable recording medium having recorded thereon a computer program for executing a method of receiving a digital signal, the method comprising:

receiving subcarrier groups modulated using radio frequency (RF) signals which have different frequencies from each other;

demodulating each of the subcarrier groups so that all subcarriers of each of the subcarrier groups are arranged adjacent to each other at baseband;

performing fast Fourier transformation (FFT) on each of the demodulated subcarrier groups independently; and

combining the subcarrier groups on which the FFT is performed.

18. An apparatus for receiving a digital signal, the apparatus comprising:

a radio frequency (RF) receiver which receives subcarrier groups modulated using RF signals which have different frequencies from each other;

a demodulator which demodulates each of the subcarrier groups so that all subcarriers of each of the subcarrier groups are arranged adjacent to each other at baseband;

a plurality of fast Fourier transformation (FFT) units which performs FFT on each of the demodulated subcarrier groups independently; and

a combiner which combines the subcarrier groups on which the FFT is performed.

19. The apparatus for receiving a digital signal of claim 18, wherein the demodulator comprises:

a plurality of mixers which frequency down-converts each of the subcarrier groups independently using the RF signals which have different frequencies from each other; and

a plurality of low-pass filters which low-pass-filters each of the frequency down-converted subcarrier groups according to a bandwidth of each of the subcarrier groups.

20. The apparatus for receiving a digital signal of claim 19, the apparatus further comprising:

a phase-locked loop (PLL) circuit which generates an RF signal; and

at least one of a frequency divider and a frequency multiplier which generates the RF signals which have different frequencies from each other using the RF signal output from the PLL circuit,

wherein the mixers modulates the subcarrier groups using the RF signals which have different frequencies from each other.