说明：  Orthogonal Frequency Division Multiplexing (OFDM) systems are more sensitive to timing and frequency offsets than single carrier systems. This Paper presents a method of joint time and frequency synchronization for OFDM systems. The synchronization technique is examined in both AWGN and multipath fading environments. Compared with conventional schemes, the proposed schemes can achieve smaller mean and mean square error (MSE) obtained by simulations.