Décodage par le treillis de codes polynomiaux: un écueil à éviter

We give a simple proof of a well known property of the maximum likelihood decoding of polynomial block codes: the systematic version of the code results in fewer decoding errors than the non systematic version. As a practical result, it is interesting to decode the systematic version of the code on the treillis of the non systematic version, because the non systematic version of the code exhibits a more regular trellis, and both version generate the same codewords.