Turbo-decoding as a numerical analysis problem

After recognizing classical turbo-decoding as fix-point iteration, alternative numerical methods such as Gauss-Seidel iteration, Jacobi over-relaxation iteration, the damped substitution method, and Newton-type methods are evaluated. None of these methods seem to perform better than fix-point iteration, and it is noticed that not even Newton's method performs better due to the presence of a random interleaver.