Turbo Decoding: Why Stopping Criteria do Work

The convergence of iterative decoding schemes is considered. The class of dually coupled codes is recalled, being a super class to both Turbo and LDPC codes. It is proven that the output L-values of a Turbo decoder cannot grow to in?nity, while those of an LDPC decoder can. Finally, a new decoder parameter is introduced by which the convergence behavior can be controlled.