Capacity of a Class of Cognitive Radio Channels: Interference Channels With Degraded Message Sets

This correspondence is motivated by two different scenarios. The first is a cognitive radio system where a cognitive radio knows a ldquodumbrdquo radio's message and the second is a sensor network in a correlated field where sensors possessing a nested message structure assist one another's information transmission. Both scenarios are modeled using the framework of discrete memoryless interference channels with degraded message sets (IFC-DMS), a setting where one of the two transmitters in an interference channel knows both the messages to be conveyed to the receivers. Both inner and outer bounds are provided for a class of IFC-DMS channels. The case of the Gaussian interference channels with degraded message sets is also investigated. In this case, achievability and converse arguments are presented for a class of ldquoweakrdquo interference channels, resulting in a characterization of this class' capacity region.