The Capacity Region of a Class of Discrete Degraded Interference Channels

We provide a single-letter characterization for the capacity region of a class of discrete degraded interference channels (DDICs). The class of DDICs considered includes the DADIC studied by Benzel in 1979. We show that for the class of DDICs studied, encoder cooperation does not enlarge the capacity region, and therefore, the capacity region of the class of DDICs is the same as the capacity region of the corresponding degraded broadcast channel.