Bidirectional relay communication with additional private message

The spectral efficiency of wireless networks can be significantly improved by wisely integrating multiple services at the physical layer. Here, we consider physical layer service integration in bidirectional relay networks, in which a relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. In the broadcast phase the relay efficiently integrates an additional private message for one node which requires the study of the bidirectional broadcast channel with additional private message. The corresponding capacity regions for discrete memoryless and MIMO Gaussian channels are derived.