Service integration in multiantenna bidirectional relay networks: Public and confidential messages

To increase the spectral efficiency of next generation wireless networks, it is important to wisely integrate multiple services at the physical layer. Here, we consider physical layer service integration in multiantenna bidirectional relay networks, where 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 additional common and confidential services at the physical layer, which requires the study of the MIMO Gaussian bidirectional broadcast channel (BBC) with common and confidential messages. We establish the secrecy capacity region which unifies previous (partial) results, where the relay provides only some of the services.