New results in the theory of identification via channels

The identification capacity is the maximal iterated logarithm of the number of messages divided by the blocklength that can be reliably transmitted when the receiver is only interested in deciding whether a specific message was transmitted or not. The identification coding theorem of R. Ahlswede and G. Dueck (1989) for single-user discrete memoryless channels states that the identification capacity is equal to the Shannon capacity. A novel method to prove the converse to the identification coding theorem is shown to achieve the strong version of the result. Identification plus transmission (IT) coding, a variant of the original problem of identification via channels, is proposed in the context of a common problem in point-to-multipoint communication, where a central station wishes to transmit information reliably to one of N terminals, whose identity is not predetermined. The authors show that as long as log log N is smaller than the number of bits to be transmitted, IT codes allow information transmission at channel capacity