Analysis of the Convergence Process by EXIT Charts for Parallel Implementations of Turbo Decoders

Iterative process is a general principle in decoding powerful FEC codes such as turbo codes. However, the mutual information exchange during the iterative process is not easy to analyze and to describe. A useful technique to help the designer is the EXtrinsic Information Transfer (EXIT) chart. Unfortunately, this method cannot be directly applied to the decoding convergence analysis if parallel processing has to be exploited for the design of turbo decoders. In this letter, an extension of the EXIT charts method is proposed in order to take into account the constraints introduced by parallel implementations. The corresponding analysis associated with Monte-Carlo simulations gives additional understanding of the convergence process for the design of parallel architectures dedicated to turbo decoding.