Fast Subspace-based Blind and Semi-Blind Channel Estimation for MIMO-OFDM Systems

This paper deals with the problem of blind and semi-blind subspace-based channel estimation, when considering MIMO-OFDM communications systems. The proposed solution offers a reduced computational complexity, mainly by a factor of the number of subcarriers, while guaranteeing accurate channel estimation as compared to state-of-the-art techniques. By exploiting the orthogonality property of the OFDM modulation, covariance matrix and noise subspace are estimated for each subcarrier in a parallel scheme, then a global cost function is minimized to obtain channel coefficients estimates. Besides, conditions for channel identifiability as well as the minimum number of subcarriers to be used for the uniqueness of the solution are investigated with various numerical simulations to corroborate our analysis.