Communication method and transmission apparatus

1. An electronic device comprising:

circuitry configured to

perform an inverse fast Fourier transform (IFFT) on N (N is an integer equal to or larger than 2) orthogonal frequency-division multiplexed (OFDM) transmission signals by IFFT circuitry of the circuitry;

perform a fast Fourier transform (FFT) on the N transmission signals which have been subjected to the IFFT;

detect phases of the N transmission signals which have been subjected to the FFT;

switch the N transmission signals away from a transmission antenna to form a feedback path between the IFFT circuitry and delay detector circuitry of the circuitry;

detect, by the delay detector circuitry, relative delay amounts of the N transmission signals from the feedback path based on the detected phases of the N transmission signals; and

adjust a timing at which at least one of the N transmission signals is subjected to the inverse fast Fourier transform based on the detected relative delay amounts.

2. The electronic device of claim 1 , wherein the circuitry is configured to supply, to N antenna elements, the N transmission signals which have been subjected to the IFFT.

3. The electronic device of claim 1 , wherein

reference signals are included in a same frequency component and a same time slot of each of the N transmission signals, and

the circuitry is configured to detect the relative delay amounts based on the reference signals included in the N transmission signals.

4. The electronic device of claim 1 , wherein the circuitry is configured to perform N− 1 division calculations on the N transmission signals and perform the FFT on an result of the N− 1 division calculations.

5. The electronic device of claim 1 , wherein the circuitry is configured to

demodulate the N transmission signals;

perform a division calculation on the N transmission signals; and

perform the FFT on a result of the division calculation.

6. The electronic device of claim 1 , wherein

reference signals are included in a same time slot of a first transmission signal and a second transmission signal,

the first transmission signal includes reference signals at a first frequency component (f 0 ) and a second frequency component (f 2 ) in the same time slot, and

the second transmission signal includes a reference signal at a third frequency component (f 1 ) in the same time slot.

7. The electronic device of claim 6 , wherein the circuitry is configured to detect a phase difference between the first transmission and the second transmission signal according to the following formula:

Phase Difference=[((Phase of f1)−(Phase of f0))/f1-f0]×(f2-f0) −(Phase of f2).

8. The electronic device of claim 7 , wherein the circuitry is configured to obtain a phase reference according to the following formula:

Phase Reference =(360 ×f0)/IFFT size.

9. The electronic device of claim 8 , wherein the circuitry is configured to adjust the timing based on a phase correction value which is obtained according to the following formula:

Phase Correction Value=mod(Phase Difference/Phase Reference), wherein

mod denotes a residue of the division between the phase difference and the phase reference.

10. The electronic device of claim 1 , wherein reference signals are assigned to a same frequency component but different successive time slots in the N transmission signals.

11. The electronic device of claim 10 , wherein the circuitry is configured to successively subject each of the N transmission signals to the FFT.

12. The electronic device of claim 11 , wherein the circuitry is configured to successively detect the relative delay amounts of the N transmission signals from differences between the N transmission signals that have successively been subjected to the FFT and a reference phase.

13. A method performed by an electronic device, the method comprising:

performing an inverse fast Fourier transform (IFFT) on N (N is an integer equal to or larger than 2) orthogonal frequency-division multiplexed (OFDM) transmission signals by IFFT circuitry of the electronic device;

performing a fast Fourier transform (FFT) on the N transmission signals which have been subjected to the IFFT;

detecting, by circuitry of the electronic device, phases of the N transmission signals which have been subjected to the FFT;

switching the N transmission signals away from a transmission antenna to form a feedback path between the IFFT circuitry and delay detector circuitry of the electronic device;

detecting, by the delay detector circuitry, relative delay amounts of the N transmission signals from the feedback path based on the detected phases of the N transmission signals; and

adjusting, by the circuitry, a timing at which at least one of the N transmission signals is subjected to the inverse fast Fourier transform based on the detected relative delay amounts.

14. The method of claim 13 ,

reference signals are included in a same frequency component and a same time slot of each of the N transmission signals, and

the relative delay amounts are detected based on the reference signals included in the N transmission signals.

15. The method of claim 13 , wherein

reference signals are included in a same time slot of a first transmission signal and a second transmission signal,

the first transmission signal including reference signals at a first frequency component (f 0 ) and a second frequency component (f 2 ) in the same time slot, and

the second transmission signal including a reference signal at a third frequency component (f 1 ) in the same time slot.

16. The method of claim 15 , further comprising:

detecting a phase difference between the first transmission and the second transmission signal according to the following formula:

Phase Difference=[((Phase of f1) −(Phase of f0))/ f1- f0]×(f2-f0) −(Phase of f2);

obtaining a phase reference according to the following formula:

Phase Reference =(360×f0)/IFFT size; and

adjusting the timing based on a phase correction value which is obtained according to the following formula:

Phase Correction Value =mod(Phase Difference/Phase Reference), wherein

mod denotes a residue of the division between the phase difference and the phase reference.

17. The method of claim 13 , wherein reference signals are assigned to a same frequency component but different successive time slots in the N transmission signals, and the method further comprises:

successively subjecting each of the N transmission signals to the FFT; and

successively detecting the relative delay amounts of the N transmission signals from differences between the N transmission signals that have successively been subjected to the FFT and a reference phase.