Low-Complexity MMSE-SIC Equalizer Employing ${\bf LDL}^{H}$ Factorization for OFDM Systems Over Time-Varying Channels

A low-complexity minimum mean square error (MMSE) equalizer with successive interference cancellation (SIC) for orthogonal frequency-division multiplexing (OFDM) over time-varying multipath channels is presented. The equalization algorithm exploits the property of matrix
$LDL^{H}$
factorization to avoid direct or recursive computation of matrix inversion, thereby reducing the computational complexity. This algorithm also allows us to exploit the band approximation of the frequency-domain channel matrix to further reduce the complexity with minor performance degradation. Theoretical analysis and simulations show that the proposed algorithms reduce the computational complexity of the MMSE-SIC scheme while preserving a good performance.