Arbitrarily varying multiple-access channels. I. Ericson´s symmetrizability is adequate, Gubner´s conjecture is true

In 1981 Jahn used the elimination technique of the first author to determine the average errors capacity region of an arbitrarily varying multiple-access channel (AVMAC), when this region has a nonempty interior. Here we remove this restriction. In his thesis (1990), Gubner (1990) missed this result because he used the first author´s first approach to the MAC, which is based on conditional decoding, and not the first author´s second approach, which is based on maximum likelihood decoding. This second approach was originally needed for a kind of compound MAC. For the AVMBC the difference between the approaches is naturally even more essential