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 LDLH 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.