Blind channel identification for cyclic-prefixed MIMO-OFDM systems with virtual carriers

This paper applies the repetition index scheme (RIS) to the channel identification of cyclic prefixed (CP) multiple-input Multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with virtual carriers (VCs) in the environment of the number of receive antennas being no less than that of transmit antennas. The VCs will cause a rank deficiency problem in computing the subspace information. With the subcarrier mapping matrix, the received signal is simplified to remove the rank deficiency. We use the RIS scheme to generate many times of equivalent symbols so the channel identification can converge with few received OFDM blocks. The RIS scheme will convert the white noise into non-white noise. With the Cholesky factorization, a noise whitening technique is developed to turn the non-white noise back to white noise. We further analyze the necessary conditions of identifiability of channel estimation. Simulations are performed to show the superiority of the proposed method.