On the Capacity of the 2-user Gaussian MAC Interfering with a P2P Link

A multiple access channel and a point-to-point channel sharing the same medium for communications are considered. We obtain an outer bound for the capacity region of this setup, and we show that this outer bound is achievable in some cases. These cases are mainly when interference is strong or very strong. In the low interference regime, a simple strategy using Gaussian codes and treating interference as noise is considered. An upper bound on the sum capacity is derived and shown to be tight (but not coinciding) with the sum-rate achievable using this scheme.