Iterative DFT-based Channel Estimation for MIMO-OFDM Systems

In multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, the conventional channel estimation techniques using comb-type preambles and interpolation between pilot subcarriers give relatively large mean square errors (MSEs) at the edge subcarriers. Furthermore, the spacing between pilot subcarriers in the frequency domain has to be close enough according to sampling theorem. To solve these problems, an DFT-based channel estimation using phase-shifted preambles in the frequency domain is proposed in this paper. At the receiver, the channel impulse responses (CIRs) of different channels can be easily distinguished in the time domain instead of in the frequency domain. Furthermore, the complete channel frequency responses (CFRs) including virtual subcarrier positions can be estimated by iterative method. Simulation results show that the proposed algorithm outperforms the conventional linear minimum mean square error (LMMSE) algorithm using comb-type preamble