In this letter, we propose a computationally effient equalization technique that employs block minimum mean squared error (MMSE) depending on LDL^H factorization. Parallel interference cancellation (PIC) is executed with pre- obtained output to provide more reliable symbol detection. In particular, the band structure of the frequency domain channel matrix is exploited to reduce the implementation complexity. It is shown through computer simulation that the proposed technique requires lower complexity than the conventional algorithm to obtain the same performance, and that it exhibits better performance than the conventional counterpart when the same complexity is assumed.