Subband adaptive equalisation with optimised alignment delays

The multi-rate subband equaliser converts the computationally complex fullband equaliser structure into several parallel low complexity subband equalisers, each operating independently. The fullband equaliser has a minimum mean square error (MMSE) dependent upon the filter coefficients and the relative delay between the desired symbol and received signal. The subband equalisers MMSE performance is also dependent upon the subband adaptive filter (SAF) coefficients and the relative delay between the desired and received subband signal components, referred herein as the alignment delay. We propose a new structure allowing implementation of independent alignment delays for each subband to achieve the MMSE with respect to both the SAF coefficients and the alignment delay. Simulation results show that the use of independent alignment delays in each subband provides significant improvement over the standard subband transversal equaliser.