Decoding options for trellis codes in the two-way relay channel

We study the application of trellis codes to physical-layer network coding in the two-way relay channel. In particular, we consider quaternary decoding on a combined trellis as an alternative to binary decoding and evaluate its gain in several scenarios, including asymmetric channels and the combination of different codes. We focus on the multiple-access phase, in which both terminals transmit their messages simultaneously, while in the second phase the relay retransmits the network-coded combination of both messages. We also evaluate the performance of both options when decoding the individual message of each terminal.