Filter bank constraints for subband and frequency-domain adaptive filters

For many years now, subband and frequency-domain adaptive filtering techniques have been proposed for the cancellation of long acoustic echoes. Classical LMS based algorithms are less attractive as their computation load is higher and the convergence behaviour for coloured far-end inputs is worse. We specify 3 realization conditions for DFT modulated subband schemes. Standard subband adaptive filters cannot fulfil all conditions. We show that frequency-domain based algorithms can be considered as a special case of subband adaptive filtering and that the realization conditions can be fulfilled in this case.