EM-based enhancement of the Wiener Pilot-Aided Channel Estimation in MIMO-OFDM systems

Pilot Aided Channel Estimation (PACE) in OFDM systems uses training sequences to estimate the channel in a subset of the frequency bins, followed by interpolation to recover the rest of the non-pilot sub-channels. Particularly, the Wiener interpolation method is based on the knowledge about channel statistics in order to find the optimal channel estimate in a frequency bin without pilot symbols in the linear MMSE sense. Nevertheless, the Wiener interpolation does not utilize the other available information at the receiver such as the received signals and the knowledge about the transmitted symbol alphabet. This paper presents a novel Expectation Maximization (EM) algorithm which optimally utilizes all available information at the receiver and thus enhances the Wiener interpolation. The proposed method is tested successfully on MIMO-OFDM systems in realistic channel conditions.