Fractionally-spaced subband and multiresolution adaptive filters

The topic of adaptive filtering is addressed for the case when the input and desired-response signals are split into several subbands, leading to a decomposition into multiple smaller adaptive filtering problems. The use of fractionally spaced adaptive filters to overcome the aliasing problem is proposed. This concept is shown to apply to the subband filtering setup. The fractional spacing idea is applied to several existing alternative approaches to the aliasing problem, leading to more economical solutions. Tree structures of subband filters are introduced to obtain multiresolution filters, and it is proposed to apply these filters to the demanding problem of acoustic echo cancellation. A three-fold gain, involving the modeling, tracking, and criterion (perception) issues, is obtained