LOW-RESOURCE DELAYLESS SUBBAND ADAPTIVE FILTER USING WEIGHTED
OVERLAP-ADD

A delayless structure targeted for low-resource implementation is
proposed to eliminate filterbank processing delays in subband adaptive
filters (SAFs). Rather than using direct IFFT or polyphase filterbanks
to transform the SAFs back into the time-domain, the proposed
method utilizes a weighted overlap-add (WOLA) synthesis.
Low-resource real-time implementations are targeted and as such do
not involve long (as long as the echo plant) FFT or IFFT operations.
Also, the proposed approach facilitates time distribution of the adaptive
filter reconstruction calculations crucial for efficient real-time
and hardware implementation. The method is implemented on an
oversampled WOLA filterbank employed as part of an echo cancellation
application. Evaluation results demonstrate that the proposed
implementation outperforms conventional SAF systems since the
signals used in actual adaptive filtering are not distorted by filterbank
aliasing. The method is a good match for partial update adaptive
algorithms since segments of the time-domain adaptive filter are
sequentially reconstructed and updated.