Fast semi-blind channel estimation for MIMO-OFDM systems with virtual carriers

Novel blind and semi-blind subspace channel estimations are proposed for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems in the presence of virtual carriers (VC). Slow convergence rate is a drawback of subspace method in deriving the noise/signal subspaces from the second-order statistics of received signals, especially when the dimension of received signals is large. In this paper, the block matrix scheme is proposed to generate a group of sub-vectors from each OFDM symbols. The dimension of sub-vectors is reduced and the number of equivalent signals is increased, and therefore, the convergence rate of channel estimation is enhanced. The semi-blind method is also developed by incorporating the subspace technology with pilot information. Computer simulations show that the proposed blind and semiblind methods converge very well in channel estimation and equalization.