Optimal and robust MMSE channel estimation for MIMO-OFDM systems

In this paper, the minimum mean square error (MMSE) channel estimation for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is investigated. We first propose an optimal MMSE channel estimation algorithm, which can fully exploit the channel correlations over space, time, and frequency domains to estimate the channel frequency response. By the principle of maximum entropy, we then design an efficient robust MMSE channel estimation algorithm, which does not need to know spatial and time correlations and has a complexity only linear in the number of subcarriers. Moreover, computer simulation shows that the robust algorithm has no significant performance degradation in comparison with the optimal algorithm.