Distributed turbo coding schemes for asymmetric two-way relay communication

We consider the time-division two-way relay communication, where two users wish to communicate to each other with the help of a common relay, for a setup, where the transmission rates of the two users can be asymmetric. All terminals operate in a half-duplex manner. The observed communication consists of three broadcast phases. During the first and second phase, each user in turn broadcasts to the opposite user and the relay. During the third phase the relay broadcasts to both users. We describe three possible schemes for performing joint network-channel coding for this time-division two-way relay channel based on turbo codes, using either network encoding after channel encoding, network encoding before channel encoding or superposition after modulation.