Patent ID: 7742391

Claim:
A method of estimating a frequency offset by a subscriber station of a communication system in which a plurality of sectors are allocated to a cell, the method comprising: extracting a preamble sequence from a downlink frame signal; estimating a phase offset of a sector to which the subscriber station belongs from among the sectors by using the preamble sequence; calculating autocorrelation values for respective signals of the preamble sequence; compensating the autocorrelation values with the phase offset; and estimating a frequency offset from the sum of phase offset compensated autocorrelation values, wherein estimating of the phase offset comprises: converting the preamble sequence into a preamble signal in the frequency domain; extracting subcarriers of respective sectors from the preamble signal; calculating sizes of the subcarriers of the respective sectors; calculating received power of the respective sectors from the sizes of the subcarriers of the sectors; comparing received power of the respective sectors and detecting a sector to which the subscriber station belongs from among the sectors; and determining the phase offset of the detected sector, and wherein the phase offset is determined by: exp ⁡ ( - j ⁢ ⁢ 2 ⁢ ⁢ π ⁢ ⁢ n × s N ) , where N indicates a number of preamble sequences, n indicates an index of the preamble sequence in a time domain, and s indicates a number for shifting of the detected sector with respect to the reference sector from among the sectors.