The LMS algorithm is considered to be robust to small disturbances if $0<mi>\backslash </mi>$mu $<mi>(</mi><mn>1</mn><mi>)</mi><mi>/</mi><mi>(</mi><mi>|</mi><mi>|</mi>$x$($n$)||^(2)).$ What

is the condition for robustness of the normalized LMS algorithm whose update formula is

hat$($w$)($n$)=$hat$($w$)($n$-1)+$tilde$(\backslash$mu $)($x$($n$))/(||$x$($n$)||^(2))$e$($n$)?$