Capacity Results for a Primary MAC in the Presence of a Cognitive Radio

The capacity region of the Gaussian cognitive interference network consisting of a primary multiple access channel and a secondary point-to-point system is considered. Its capacity region with weak interference is known. In this paper, the capacity region of a sub-regime of the strong interference regime is studied. An outer bound on the capacity region of this setup with strong interference is derived. An inner bound is shown to coincide with the strong interference outer bound under some conditions, thus characterizing the capacity of this setup for a set of channel parameters.