An algorithm for determining if a rate (n-1)/n punctured convolutional encoder is catastrophic

The algorithm determines whether or not the punctured state diagram contains a zero-weight cycle. The punctured encoder is assumed to be obtained from a rate 1/b, b⩽n, antipodal encoder of a given constraint length. The algorithm is much simpler to implement in software than the previously known method of calculating the GCD of the determinants of the n distinct (n-1)×(n-1) submatrices of the generator matrix. The computational complexity of the algorithm is no worse than the computational complexity of the GCD method for relatively short constraint lengths, that is, the constraint lengths for which the Viterbi algorithm is implemented