Tap-length optimization of adaptive filters used in stereophonic acoustic echo cancellation

An adaptive filter with a large number of weights or taps is necessary for stereophonic acoustic echo
cancellation (SAEC), depending on the room impulse response and acoustic path where the cancellation
is performed. However, a large tap-length results in slow convergence and increases the complexity of
the tapped delay line structure for FIR adaptive filters. To overcome this problem, there is a need for an
optimum tap-length-estimation algorithm that provides better convergence for the adaptive filters used
in SAEC. This paper presents a solution to the problem of balancing convergence and steady-state performance
of long length adaptive filters used for SAEC by proposing a new tap-length-optimization algorithm.
The optimum tap length and step size of the adaptive filter are derived considering an impulse
response with an exponentially-decaying envelope, which models a wide range of acoustic echo paths.
The tap-length optimization is applied to a single long adaptive filter with thousands of coefficients to
decrease the total number of weights, which in turn reduces the computational load. To further increase
the convergence rate, the proposed tap-length-optimization algorithm is applied to an existing multiple
sub-filter-based echo canceller, for which we present a convergence analysis. Computer simulations are
also presented, comparing the proposed approach with related work.