Patent ID: 7643566

Claim:
An apparatus for estimating a frequency offset in an Orthogonal Frequency Division Multiplexing (OFDM) system, comprising: an observation-window setting unit for outputting at least two time domain signals comprising a delay time difference from a received signal through first and second observation windows with different delay times; a first compensator for compensating the two time domain signals using at least one candidate frequency offset of a plurality of candidate frequency offsets; a Fourier transformer for transforming the two compensated time domain signals to two frequency domain signals; a second compensator for compensating the frequency domain signal for the second observation window using the at least one candidate frequency offset and compensating the compensated frequency domain signal for a phase difference based on the delay time difference; a comparator for comparing the frequency domain signal for the first observation window with the compensated frequency domain signal for the second observation window, and outputting a magnitude difference value; and a controller for controlling frequency compensations of the first and second compensators with the plurality of candidate frequency offsets, and estimating a candidate frequency offset, mapped to a minimum difference value among difference values output from the comparator, as an optimal frequency offset; wherein the difference values are mapped to the plurality of candidate frequency offsets.