Joint fine time synchronization and channel estimation for MIMO-OFDM WLAN

Fine time synchronization for the OFDM (orthogonal frequency division multiplexing) system is carried out by taking correlation between the received sequence and a reference sequence. This conventional method shows unsatisfactory performance in a WLAN (wireless local area network) environment due to the large value of RMS delay spread. The paper proposes an algorithm to improve the performance of the estimator by exploiting the characteristics of the channel. We also present a channel estimation algorithm in the time domain for MIMO-OFDM (multiple-input multiple-output OFDM) with the same complexity as that in a single antenna system. The simulation results show: (1) for symbol time synchronization, the probability of incorrect timing in the proposed algorithm is hundreds of times lower than that in the conventional algorithm; (2) for channel estimation, with the use of two consecutive training sequences as in standard IEEE 802.11a, there is 3 dB decrease in SNR to achieve the same MSE as in the case of only one training sequence.