ISSN : 1796-2048
Volume : 2    Issue : 2    Date : April 2007

Fast Efficient Coefficient Update for Filtered-X Affine Projection Algorithms
Miguel Ferrer, Alberto Gonzalez, Maria de Diego, and Gema Pinero
Page(s): 83-89
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An efficient version of the affine projection (AP) algorithm, which is called FXAP-AC throughout the
paper, is presented. This algorithm uses the filtered-x structure instead of the modified structure
which is required for the implementation of the AP algorithm when the desired signal is not
available, for instance in Active Noise Control (ANC) applications. The conventional AP algorithm for
ANC, which is based on the modified structure (MFXAP), provides good performance. However the
filtered-x structure is advisable for practical cases since it achieves a meaningful computational
saving avoiding the additional filtering needed by the modified structure without significantly affect
the performance in practice. This fact is specially important in multichannel applications where the
computational resources are limited. Furthermore, different low-cost strategies already proposed in
the conventional AP algorithm such as the fast error vector calculation or the efficient computation of
coefficient update can be applied to the FXAP. Throughout this paper, the efficient computation of
coefficient update is developed for the FXAP (resulting in the FXAP-AC). This strategy can be
meaningfully combined with others previously reported to achieve very fast and robust FXAP
algorithms. Experimental results validate the use of the proposed algorithm for practical

Index Terms
affine projection algorithms, fast algorithms, auxiliary coefficients, filtered-x structure, active noise