On maximal error capacity regions of Symmetric Gaussian Multiple-Access Channels

We prove a computable inner bound for the maximal error capacity region of a Symmetric Gaussian Multiple-Access Channel (SGMAC). The main idea behind our results is successive cancellation in decoding involving decoding of only one message set first while regarding the other message set as interference followed by a cancellation of the effect of the decoded message. Specifically, the inner bound is obtained through a connection between the SGMAC and another point-to-point Gaussian Channel with Interference (GCI) model introduced here. The bound takes the form of a pentagon strictly inside the average error capacity region.