#### STEPSIZE CONTROL IN BLIND SOURCE SEPARATION

Thomas P. von Hoff 1 , Allen G. Lindgren 2 , and August N. Kaelin 1

fvonhoff, kaeling@isi.ee.ethz.ch lindgren@ele.uri.edu

The behavior of the classic algorithm for blind source sep
aration (BSS) is detailed for a fixed step size. To improve
the algorithm in speed and exactness, essential in tracking a
timevarying mixing environment, a variable step size must
be employed. The ideal step size should decrease or in
crease as the overall system error decreases or increases. It
is shown analytically that the coefficients of the estimating
function provide a "measure of error" that is available to
automatically control the algorithm step size. This paper
proposes a selfadjusting, timevarying step size that is built
from the square of the running average of the coefficients of
the estimating function. Error free convergence is achieved
for a timeinvariant environment. The ability of the algo
rithm to improve the convergence in a timeinvariant mixing
environment and to track a changing mixing environment is
demonstrated by extensive simulation results.