New viewpoint on communication channel capabilities

A channel modeling technique is described that looks at the communication problem from a new viewpoint. A quantity called unfolding capacity--the capacity of a channel as it happens to unfold--is defined. A theorem is derived that proves for the assumed channel model, a feedback scheme can be devised that for sufficiently large
N
, achieves arbitrarily Iow probability of error at any rate less than unfolding capacity, no matter what capacity happens to unfold. The theorem also proves that this type of performance can not be achieved without feedback.