Two Contributions to Error Exponents for Asynchronous Multiple Access Channel

The following conjectures from previous work of the authors are proven, enhancing the relevance of results there on the subject in the title: (i) The error exponents previously derived assuming that consecutive messages could be encoded using different codebooks, are also achievable with each sender using only one codebook. (ii) In case the senders could be synchronized, controlled asynchronism (a deliberate shift of codewords) may admit to achieve error exponents unachievable by synchronous transmission.