Adaptive constellation scheme for two-way relay communications

In this paper, an adaptive constellation scheme for two-way relay communication systems with asymmetric channels is proposed. In this scheme, each node transmits codeword generated by the same turbo encoder to a relay node using different signal power and the relay node decodes the received codeword from each node. Then, the relay node re-encodes and combines these two decoded data sequences using new constellation mapping and broadcasts the resulting signal to each node. This new constellation scheme adaptively adjusts the power level for each user's data by considering the channel conditions. It is shown that the proposed scheme has better frame error rate than the fixed constellation case and XOR case.