Stability analysis of the turbo decoding algorithm using Max-Log-MAP

In this paper we investigate analytically the convergence properties of the iterative turbo decoding with the Max-Log-MAP algorithm for soft-output generation. With respect to the iterative decoding scheme, several equivalent mathematical formulations are derived to facilitate the stability analysis, based on which we show that turbo decoding with Max-Log-MAP has at least one fixed point but is in general suboptimal and may not even converge. Finally, some conditions are given to guarantee the convergence of the iterative turbo decoding.