The Strong Interference Channel With Common Information

Transmitter cooperation enabled by dedicated links with finite capacities allows for a partial message exchange between encoders. After cooperation, each encoder will know a common message partially describing the two original messages, and its own private message containing the information that the encoders were not able to exchange. We consider the interference channel with both private and common messages at the encoders. A private message sent at an encoder is intended for a corresponding decoder whereas the common message is to be received at both decoders. We derive conditions under which the capacity region of this channel coincides with the capacity region of the channel in which both private messages are required at both receivers. We show that the obtained conditions and the strong interference conditions determined by Costa and El Gamal for the interference channel with independent messages are satisfied by the same class of interference channels.