On Capacity Regions of Discrete Asynchronous Multiple Access Channels
  A general formalization is given for asynchronous multiple access channels which admits different assumptions on delays. This general framework allows the analysis of so far unexplored models leading to new interesting capacity regions. In particular, a single letter characterization is given for the capacity region in case of 3 senders, 2 synchronous with each other and the third not synchronous with them. 
L\'or\'ant Farkas, Tam\'as K\'oi
cs.IT math.IT