The concept of bidirectional relaying is becoming more and more attractive since it has the potential to significantly improve the overall performance and coverage in wireless networks such as ad-hoc, sensor, and even cellular systems. This is mainly based on the fact that it advantageously exploits the property of bidirectional communication to reduce the inherent loss in spectral efficiency induced by half-duplex relays.
Bidirectional relaying applies to three-node networks, where a half-duplex relay node establishes a bidirectional communication between two other nodes using a decode-and-forward protocol. There, in the initial multiple access (MAC) phase, two nodes transmit their messages to the relay node, which decodes them. In the succeeding bidirectional broadcast (BBC) phase, the relay re-encodes and transmits both messages in such a way that both receiving nodes can decode their intended message using their own message from the previous phase as side information. It is shown that capacity is achieved by a single data stream that combines both messages based on the network coding idea. This concept breaks with the common model to regard information flows as "fluids" and constitutes a paradigm shift.