Method and apparatus for compensating for residual frequency offset in an OFDM system
Disclosed is a method for compensating for a residual frequency offset in an orthogonal frequency division multiplexing system comprising the steps of: a) performing a fast fourier transform for an input signal to convert the input signal into a serial signal; b) detecting signal power of the serial signal to control the passthrough a signal greater than a predetermined critical value; c) selecting each section of a quadrant for each passed signal; d) estimating a phase error in each section of the quadrant for one orthogonal frequency division multiplexing symbol with respect to the selected section of the quadrant; and e) frequency-oscillating a signal based on the estimated phase error, generating the input signal by multiplying an oscillated signal by a band-passed signal, and then returning to step a).
1. A method for compensating for a residual frequency offset in an orthogonal frequency division multiplexing system, comprising the steps of:
a) performing a fast Fourier transform for an input signal to convert the input signal into a serial signal;
b) detecting signal power of the serial signal to control the pass through of a signal greater than a predetermined critical value;
c) selecting a section of a quadrant for each passed signal;
d) estimating a phase error in each section of the quadrant for one orthogonal frequency division multiplexing symbol with respect to the selected section of the quadrant; and
e) frequency-oscillating a signal based on the estimated phase error, generating the input signal by multiplying an oscillated signal by a band-passed signal, and returning to step a).
2. The method as claimed in claim 1 , wherein step a) includes the steps of:
f) converting the input signal into a digital signal;
g) converting the digital signal into parallel signals; and
h) performing a fast Fourier transform on the parallel signals and converting the parallel signals into a serial signal.
3. The method as claimed in claim 1 , wherein the power detection in step b) is performed by,
|Y m (k)| 2 >τ,
where Y m (k) represents an k th subcarrier signal of an m th orthogonal frequency division multiplexing symbol and τ represents a critical value.
4. The method as claimed in claim 2 , wherein the power detection in step b) is performed by,
|Y m (k)| 2 >τ,
where Y m (k) represents an k th subcarrier signal of an m th orthogonal frequency division multiplexing symbol and τ represents a critical value.
5. An apparatus for compensating for a residual frequency offset in an orthogonal frequency division multiplexing system, the apparatus comprising:
a fast Fourier transform unit for performing a fast Fourier transform for an input signal to convert the input signal into a serial signal;
a power detector for detecting signal power of an output signal of the fast Fourier transform unit to control the passthrough of a signal greater than a predetermined critical value;
a quadrant detector for selecting a section of a quadrant for each passed signal;
a phase error estimation unit for estimating a phase error in each section of the quadrant for one orthogonal frequency division multiplexing symbol with respect to the selected section of the quadrant; and
a voltage controlled oscillator for frequency-oscillating a signal based on the estimated phase error, generating the input signal by multiplying an oscillated signal by a band-passed signal, and inputting the input signal to the fast Fourier transform unit.
6. The apparatus as claimed in claim 5 , wherein the phase error estimation unit estimates the phase error by using a SNR signal greater than a predetermined critical value and a representative signal located on a diagonal axis of a constellation plot.
7. A computer program device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform the method steps for a method for compensating for a residual frequency offset in an orthogonal frequency division multiplexing system, comprising the steps of:
a) performing a fast Fourier transform for an input signal to convert the input signal into a serial signal;
b) detecting signal power of the serial signal to control the pass through of a signal greater than a predetermined critical value;
c) selecting a section of a quadrant for each passed signal);
d) estimating a phase error in each section of the quadrant for one orthogonal frequency division multiplexing symbol with respect to the selected section of the quadrant; and
e) frequency-oscillating a signal based on the estimated phase error, generating the input signal by multiplying an oscillated signal by a band-passed signal, and returning to step a).