From the above derivation, we observe that if the orthonormality holds, RLS algorithm can be reduced to a form of LMS algorithm. Since the approximation is applied during the derivation, we expect some performance degradation in the convergence speed. We will show the performance of the proposed algorithm in next section. In (31), there is a division operation when implementing 1/n. To further simplify the proposed algorithm, we can approximate 1/n with a piecewise function δ(n), which is designed as follows