Decode-and-forward strategies for bidirectional relaying

We consider a three-node network, where a relay node establishes a bidirectional communication between two nodes using a two-phase decode-and-forward protocol. In the first phase the two nodes transmit their messages to the relay node which decodes them. Then the relay broadcasts the information to both nodes in the succeeding phase which we call the bidirectional broadcast channel. In this work we first consider both phases separately and compare existing strategies especially for the second phase. We determine the capacity region of the bidirectional broadcast channel and discuss the impact of multiple antennas and the correlation between the channels on the capacity region. We show how the available spectral resources can be shared between the two phases and compare achievable rate regions for the whole bidirectional communication. Finally, we indicate how the bidirectional relay communication and the knowledge about the corresponding rate region can be advantageously used in cellular systems or cross-layer designs.