The present invention relates to a preamble structure and method for improving symbol timing synchronization estimation performance in an OFDM-FDMA / CDMA / TDMA system. The present invention relates to a symbol timing estimation of a downlink preamble in a system based on an OFDM-FDMA / CDMA / TDMA system. In the method, a preamble structure using a characteristic of symmetry and conjugate complexes to an existing preamble structure (Equation 1, P 1 = [AA]) in which a pattern is repeated once in an existing time domain after passing an inverse fast Fourier transform (IFFT) (math Setting Equation 5, P 2 = [A'B * A'B *]); And a symbol timing estimation algorithm proposed in the preamble structure using the characteristics of the symmetry and conjugate complex numbers (Equation 6, )). Through this, the downlink preamble structure and algorithm proposed by the OFDMA-based system improve the detection probability performance even at the SNR lower than the conventional detection probability performance.;OFDM, FDMA, CDMA, TDMA, Preamble, Time Synchronization, Symbol Timing Estimation
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