On Gaussian Multiple Access Channels with Interference: Achievable Rates   and Upper Bounds
  We study the interaction between two interfering Gaussian 2-user multiple access channels. The capacity region is characterized under mixed strong--extremely strong interference and individually very strong interference. Furthermore, the sum capacity is derived under a less restricting definition of very strong interference. Finally, a general upper bound on the sum capacity is provided, which is nearly tight for weak cross links. 
Anas Chaaban, Aydin Sezgin, Bernd Bandemer, Arogyaswami Paulraj
cs.IT math.IT