On delayless subband adaptive filtering by subband/fullband transforms

Delayless subband adaptive digital filters (ADFs) have been proposed to avoid the drawbacks of the conventional subband ADF, which are transmission delay associated with the filterbank and degradation of the performance due to aliasing effects. In the delayless subband ADF, the tap-weight vectors are computed in subbands and then they are transformed into the tap-weight vector in fullband by a certain transform. In this letter, a general formulation for the delayless subband ADF is proposed, and some requirements on the fullband/subband transform are investigated.