Coding Strategies for Bidirectional Relaying for Arbitrarily Varying Channels

In this work we study optimal coding strategies for bidirectional relaying under the condition of arbitrarily varying channels. We consider a three-node network where a relay node establishes a bidirectional communication between two nodes using a spectrally efficient decode-and-forward protocol. In the first phase the two nodes transmit their messages to the relay node, which decodes them. In the succeeding bidirectional broadcast phase the relay node broadcasts an optimal re-encoded composition of them so that both nodes can decode the intended message using their own message as side information. We assume that the whole communication is affected by channels which vary in an unknown and arbitrary manner during the transmission so that all nodes have only imperfect channel state information. For both phases of the bidirectional relaying protocol we present robust coding strategies, which mitigate the uncertainty in channel state information so that reliable communication can be guaranteed. Further, we characterize the corresponding capacity regions for random and deterministic coding strategies.