On identification via multiway channels with feedback

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