A low-complexity symbol time estimation for OFDM systems

Conventional symbol time (ST) synchronization algorithms for orthogonal frequency-division multiplexing (OFDM) systems mostly are based on maximum correlation result of the cyclic prefix. Due to the channel effect, one needs to further identify the channel impulse response (CIR) so as to obtain a better ST estimation. Overall, the required computational complexity is high because it involves correlation operation, as well as the fast Fourier transform (FFT) and inverse FFT (IFFT) operations. In this work, without the FFT/IFFT operations and the knowledge of CIR, a low-complexity time-domain ST estimation is proposed. We first characterize the frequency-domain interference effect as a function of the ST by deriving some analytical equations considering the channel effect. Based on the derivation, the new method locates the symbol boundary at the sampling point with the minimum interference in the frequency-domain. Moreover, for reducing the computational complexity, the proposed frequency-domain minimum-interference metric is converted into a low- complexity time-domain metric by utilizing the Parseval´s theorem and the sampling theory. Simulation results exhibit high performances for the proposed algorithm in the multipath fading channels.