Abstract
Summary form only given. The authors let the number of fundamental paths of weight d in a convolutional code be denoted by Ad and let α be defined by lim sup log A d /d = log α as d → α. They have observed experimentally that the α's for codes of fixed constraint length and rate are very nearly equal and seem to approach a limit for very large constraint length. To explain this, they have studied the ensemble of fixed convolutional codes as a subset of the ensemble of time-varying convolutional codes.