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Channel Estimation for Space-Time Block Coded OFDM Systems using Few Received Symbols

A novel subspace channel estimation is proposed for space-time block coded (STBC) multiple-input multiple–output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Considering the zero-padding technique, the signal model of the STBC-OFDM system is first studied. The major drawback of the subspace method is the slow convergence which requires a large number of received symbols to compute the noise subspace. The repetition index scheme is developed here to increase the number of equivalent received symbols. Using the space-time coding property, the forward-backward method is presented to improve the convergence speed further. Moreover, the repetition index scheme transforms the white noise into non-white one. The noise prewhitening technique is proposed to reduce the non-white noise effect. Computer simulations show the effectiveness of the proposed forward-backward method and noise prewhitening technique.