EM based channel estimation method for MIMO-OFDM systems

Standard Wiener interpolation for Pilot Aided Channel Estimation (PACE) in OFDM systems does not utilise other available information at the receiver Such its the received signals in the non-pilot sub-channels and the knowledge about the transmitted symbol alphabet. In addition, the standard Wiener interpolation method requires he spacing of the pilot symbols to satisfy the Sampling Theorem, i.e. at least two Pilot subchannels within the coherence bandwidth. This paper presents two novel channel estimation methods aiming at improving and expanding the PACE. The first method is based on the standard Wiener interpolation. and it achieves better performance by feeding hack the posterior probabilities of the detected symbols. The second method is aiming at performing channel estimation with the placement of pilot symbols not necessarily satisfying the Sampling Theorem. Both methods Use the Expectation and Maximisation (EM) algorithm. Copyright (C) 2007 John Wiley & Sons. Ltd.