A subspace method for channel estimation in soft-iterative receivers

In this paper we propose a new soft method for the estimation of block-fading channels based on multi-block (MB) processing. The MB estimator [1] exploits the invariance of the subspace spanned by the multipath components of the channel and it estimates the channel subspace by sample averaging over a frame of blocks. Here the MB method is extended to incorporate also soft information, which is available in iterative (turbo) equalizers. The mean square error (MSE) of the soft-based estimate is evaluated analytically and validated by simulations. The comparison with the conventional training-based block-by-block estimate shows the benefits of the proposed approach on the turbo equalizer convergence