Patent ID: 8737543

Claim:
An apparatus for recovering an estimated velocity of a mobile station in a communication system, the apparatus comprising: a searcher for determining a Doppler shift value representing the estimated velocity of the mobile station by using a channel impulse response of a preamble signal received at a regular interval of time; a detector for determining a reference Doppler value for compensating the Doppler shift value by using correlation ratios between channel values of symbols to which data for the mobile station are allocated according to subcarriers in a data allocation field of a frame including the preamble signal; and a compensator for determining a compensated Doppler shift value by using the reference Doppler value to compensate the Doppler shift value for a folding value, wherein the folding value represents a difference between the estimated velocity and a true velocity of the mobile station, wherein the compensator sets a maximum value representing a maximum allowable value of the Doppler shift value, determines a folding frequency representing a frequency position where aliasing occurs, determines frequency-domain folding intervals having a spacing of the folding frequency, in which the Doppler shift value is to be compensated for the folding value within a range up to the maximum value, determines if the reference Doppler value falls within each of the folding intervals, and if the reference Doppler value falls within a corresponding folding interval, determines the compensated Doppler shift value by using the folding frequency, an index of the corresponding folding interval, and the Doppler shift value, and wherein each of the folding intervals represents an interval that is equal to or greater than the folding frequency times the index of the corresponding folding and is less than the folding frequency times the index plus 1, and the folding frequency is determined as a reciprocal number of two times the regular interval of time.