On classes of convolutional codes that are not asymptotically catastrophic

Denote by w 0 the minimum average weight per edge over all nonzero cycles in the state diagram for a convolutional code, and assume that a technique is available for generating canonical parity-check matrices for codes with increasing degree m. The obtained class of codes is asymptotically catastrophic if w 0 approaches zero for large m. In this paper we prove the existence of convolutional code classes that are not asymptotically catastrophic by providing explicit constructions of codes with nonzero w 0 for all m.