Timing Synchronization for MIMO-OFDM WLAN Systems

In the paper, a novel timing synchronization method is proposed for MIMO-OFDM based wireless local area networks (WLAN) systems. For coarse timing synchronization, a sliding window differentiator is used after a conventional autocorrelation device so that the timing ambiguity caused by the auto-correlation metric plateau can be removed. For fine timing synchronization, a metric called signal-to-interference ratio (SIR) is devised. Based on this metric, a fine timing synchronization method is developed to improve the timing precision. Compared with the conventional cross-correlation synchronization methods, this method is more robust to multipaths and pseudo multipaths caused by the cyclic delay diversity (CDD) scheme, which may be adopted in the next generation WLAN IEEE 802.11n system. At last, the timing is refined to precisely estimate the time of arrival for location applications by searching the cross-correlation peak in a small window around the fine timing estimation.