On the Capacity of Type I Broadcast-Z-Interference Channels

The capacity of a network in which a degraded broadcast channel generates interference to a single-user channel is studied. An achievable rate region based on superposition coding and joint decoding is derived for the discrete case. Outer bounds on the capacity region are obtained for different degradedness conditions. For the Gaussian case, the capacity regions are obtained for very strong and slightly strong interference cases. When the interference is moderate or weak, some boundary points of the capacity regions are determined. For all the obtained capacity results, it is shown that to achieve the capacity, the interference should be fully decoded when it is strong, partially decoded when it is moderate, and treated as noise when it is weak.