Precoding for convolutional codes

The study the distance relations between the input sequences and the code sequences in convolutional codes. Namely, starting from some encoder realization of a code, we investigate the effect of inserting a precoder before the encoder. The precoder is a one-to-one operation on input sequences, and it may have memory. We show how the precoder affects the bit error rate of the input and the level of protection of the input subsequences.