An error propagation prevention method for MIMO-OFDM RLS-DDCE-algorithms

In this paper issues in the implementation of a recursive least squares (RLS) multiple-input multiple-output (MIMO) decision-directed channel estimation (DDCE) and tracking algorithm for spatial multiplexing are discussed. Problems addressed are a simple calculation of the inverse autocorrelation matrix and schemes of training data or pilot symbols. While there is much work spend in evaluating pilot performances, the choice of pilot symbols cannot be decided based only on simulations. Three proposed schemes are discussed regarding off-the-shelf RF components´ compatibility of an experimental MIMO system where polyphase pilots fail to yield good results. Because decision-directed channel estimation is prone to error propagation, we propose a scheme which makes a check on recovered symbol plausability by using the result from the channel decoder thus preventing error propagation.