For the case of complete feedback, a fairly unified theory of identification is presented. Its guiding principle is the discovery that communicators (sender and receiver) must set up a common random experiment with maximal entropy and use it as randomization for a suitable identification technique. It is shown how this can be done in a constructive manner. The proof of optimality (weak converse) is based on a novel entropy bound, which can be viewed as a substitute for Fano's lemma in the present context. The single-letter characterization of (second-order) capacity regions now rests on an entropy characterization problem, which often can be solved. This is done for the multiple-access channel with deterministic encoding strategies, and for the broadcast channel with randomized encoding strategies.>

An inner bound to the capacity region for identification via a broadcast channel with feedback and a soft outer bound to the capacity region of a general broadcast channel without feedback are established, allowing randomized encoding in both cases. These results can be combined to determine the identification capacity region for the deterministic broadcast channel; the set of achievable second-order rate pairs (R/sub 1/,R/sub 2/) for the deterministic broadcast channel is given by the constraints 0>