Patent ID: 7561628

Claim:
A subscriber station (SS) apparatus in a broadband wireless communication system, comprising: a preamble subcarrier acquirer for extracting subcarrier values having a preamble code from a fast Fourier transform (FFT) signal; a multiplier for code-demodulating the subcarrier values by multiplying the subcarrier values by a preamble code; a correlator for calculating n th -order differential correlations by calculating a correlation between two subcarrier values spaced by n over all cases in a code-demodulated signal and summing the calculated correlations, where 1≦n≦n max ; an inverse fast Fourier transform (IFFT) processor for IFFT-processing the n th -order differential correlations from the correlator and outputting an IFFT signal; and a maximum value detector for detecting a maximum value from the IFFT signal and calculating a timing offset using an IFFT output index having the maximum value; wherein if n is a J-point IFFT input index, . . . differential correlations (Z n ) by Z n =. . . .