Space-Time Block Coded MIMO ZP-based OFDM Systems for Complex Input Signals

A novel semi-blind channel estimation is proposed for space-time block code (STBC) multiple-input multiple-output (MIMO) zero-padded orthogonal frequency division multiplexing (ZP-OFDM). With a modified STBC scheme, the channel responses of MIMO STBC-OFDM systems are shown to be identifiable up to two ambiguity matrices by the subspace channel estimation. With the estimated channel, the frequency domain minimum mean-square error (MMSE) filter is then computed to detect the OFDM symbols. Furthermore, we propose a forward-backward averaging technique to enhance the performances of blind channel estimation and MMSE filter. Computer simulations are given to demonstrate the effectiveness of the channel estimation and receiver design for the ST-coded MIMO OFDM system.