Robust Timing Synchronization Preamble for MIMO-OFDM Systems Using Mapped CAZAC Sequences

Orthogonal frequency division multiplexing system provides a promising physical layer for 4G and 3GPP LTE systems in terms of efficient use of bandwidth and high data rates, this technology suffers from Inter Symbol Interference and Inter Carrier Interference. On the other hand, multiple input multiple output system is deployed along with orthogonal frequency division multiplexing in the new 802.11n standard, which offers many advantages over conventional standards such as 802.11g Wireless LAN. The main challenge of such system is the synchronization between the transmitter and the receiver [1]. A bad timing synchronization causes the loss of a lot of information in a MIMO-OFDM system. In this paper, a robust timing synchronization method is proposed for a MIMO-OFDM systems up to 8 × 8 as well, where Nt is the transmit antennas and Nr is the receive antennas. The proposed method is based on transmit a mapped orthogonal constant amplitude zero auto correlation sequences over different transmit antennas. The simulations results show that the proposed method has high performance to detect the timing synchronization even at very low signal to noise ratio in additive white Gaussian noise and multipath fading Rayleigh channels. Furthermore, simulation results for our proposed method present a robust timing synchronization against existing methods at a low SNR and for MIMO-OFDM system up to 8×8, which the coarse and fine timing synchronization are done at the same time at each receive antenna due to the orthogonality of different training sequences transmitted over different transmit antennas.