Fig. 5(a) indicates that RLS algorithm converges quickly and steady. In addition, the RLS algorithm with orthonormal polynomials converges faster than that with conventional polynomials as the orthonormal basis functions can improve the numerical stability. LMS algorithm converges quickly but unsteady when the step size δ =0.05. On the contrary, LMS algorithm converges steady but slowly when the step size δ =0.005. The proposed algorithm achieves almost the same performance as that of the RLS algorithm. Moreover, the proposed algorithm with δ(n) converges a bit slowly than the proposed algorithm with 1/n does.