An algebraic construction of rate1/v-ary codes; algebraic construction (Corresp.)
JØrn Justesen · IEEE Transactions on Information Theory · 1975
If the constraint length of a convolutional code is defined suitably, it is an obvious upper bound on the free distance of the code, and it is sometimes possible to find codes that meet this bound. It is proved here that the length of a rate1/ u q-ary code with this property is at mostq u, and we construct a class of such codes with lengths greater thanq u/3.