Blind CFOs Estimation by Capon Method for Multi-User MIMO-OFDMA Uplink System

This letter presents a blind carrier frequency offset (CFO) estimator for multi-user multiple input multiple output-orthogonal frequency division multiple access (MIMO-OFDMA) uplink system by Capon method using covariance matrix decomposition in the presence of Rayleigh fading channel. In this method, a covariance matrix is derived from the received signal, followed by QR factorization of the covariance matrix to get the upper triangular matrix. Then, a cost function is formulated by calculating the inverse of the upper triangular matrix. The proposed estimator does not require channel state information or any pilot symbols, which makes the system spectrum efficient. The exact Cramer Rao lower bound is also derived, establishing a lower limit for the mean squared error of the proposed estimator. Simulation results indicate that our proposed method outperforms existing methods. The proposed method also provides a lower computational complexity.