Determine if a convolutional code causes catastrophic error propagation.

Create the trellis for the standard, rate 1/2, constraint length 7 convolutional code.

t = poly2trellis(7,[171 133]);

Verify that the code is not catastrophic.

iscatastrophic(t)

ans = logical
   0

Create a trellis for a different convolutional code using the poly2trellis function.

u = poly2trellis(7,[161 143]);

Verify that the code is catastrophic.

iscatastrophic(u)

ans = logical
   1