Time and frequency selective channels or doubly selective channels leads to inter-carrier interference(ICI) in orthogonal frequency division multiplexing (OFDM) systems. We investigate how effectively turbo equalization could reduce the complexity burden of frequency domain equalization in the presence of doubly selective fading channels. We split the frequency domain matrix into several small sub-matrices that contain significant channel information and combine the MMSE equalization and the MAP decoding for iterative structure based on sub-matrices of frequency domain channel matrix. Simulation results show how much complexity reduction the iterative method can offer with better BER performance than that of the non iteration method. The iterative method has 70% computational complexity reduction with achieving IdB performance improvement in our simulations.