A technique to evaluate an exact formula for the bit error rate of convolutional codes in case of finite length words

A technique for calculating the exact performance of the Viterbi algorithm when applied to a convolutional code is described. More precisely, we propose a suitable modification of the Markov chain, which permits, for any value L of the considered codeword length, to derive easily a closed form expression for the bit error rate as a function of L. Finally some promising applications are also presented in order to evaluate the performance of practical encoding schemes.