Robust second-order blind equalization of polyphase channels

This work deals with the problem of linear polyphase blind equalization (BE), i. e. we are interested in equalizing the output of a single-input-multiple-output (SIMO) channel, without observing its input. A recent result by Liu and Dong [1] showed that if the sub-channel polynomials are co-prime, the equalizer output whiteness suffices for the equalization of a white input. Based on this observation, we propose a simple decorrelation criterion for second-order based blind equalization. Due to its second-order nature, this criterion is insensitive to the distance of the input from Gaussianity, hence it performs BE even for Gaussian or non-Gaussian inputs. Moreover, unlike other second-order techniques, our approach bypasses channel estimation and computes directly the equalizer. By doing so, it avoids the problem of ill-conditioning due to channel order mismatch which is crucial to other techniques. Combined to its good convergence properties, these characteristics make the proposed technique an attractive option for robust polyphase BE, as evidenced by both our analysis and computer simulation results.