An efficient preamble design for timing synchronization in MIMO-OFDM systems

In this paper, we propose an efficient preamble structure for improving the timing synchronization in Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. The proposed short preamble symbol consists of four equal duration sub symbols, the first and third of which are CAZAC sequences. The second sub symbol is comprised of PN sequences. The fourth sub symbol consists of CAZAC sequence weighted with PN sequence which has been multiplied by a scrambling function. The additional scrambling operation is performed to improve the performance of the system. The correlation property of the sequences used as training symbol ensures that the proposed timing metric has its peak value at the correct symbol starting point. When compared with the conventional Schmidl´s and Minn´s methods, the simulation result of the proposed method could provide sharper correlation peak in both AWGN and Rayleigh channels. Hence a better timing synchronization can be achieved. The estimation performance is also evaluated by computing the Correct Detection Rate (CDR).