A Novel Channel Estimation and Equalization for MIMO-OFDM Systems

Abstract

Multiple-input multiple-output (MIMO) technique combined with orthogonal frequency division multiplexing (OFDM) modulation has a great potential for the coming broadband wireless communications standard. However, MIMO-OFDM system inherits the weakness of the OFDM to channel time-variation. Therefore, channel estimation is a key problem in MIMO-OFDM systems. In this paper, we propose an effective stagger time domain pilot structure, which can avoid the time domain cross interference in pilot section, thus help the channel estimator to obtain uncorrupted channel fading envelopes. Based on these estimates, the cascaded equalizer must eliminate both the ICI and the cross interference among the antennas to recover the transmitted signals. Here, by sufficiently exploiting the underlying structure of system transfer matrix, we propose a downsizing minimum mean square error (MMSE) equalizer, which can not only achieve the satisfied approximation to the conventional MMSE equalizer, but also reduce the computational complexity significantly. The validity of the proposed pilot structure and the downsizing MMSE equalizer is demonstrated by computer simulations.