A cognitive two-way relay transmission scheme based on adaptive QAM and wireless network coding

In this paper, we investigate a cognitive radio network design for the Two-way Relay (TWR) Channel, relying on the combination of Adaptive Quadrature amplitude modulation (AQAM) and network coding technique. More explicitly, we extend the AQAM in peer-to-peer transmission scenario to the downlink design of Decode-and-Forward Two-way Relaying (DF-TWR) scenario. On the basis of the bit-error-ratio (BER) bounds, joint power and rate adaptive QAM with network coding scheme is proposed for the purpose of improving the throughput of the relaying system. In addition, Network-coded-aided QAM suffers a modest SNR loss due to the direct current (DC) bias, which will be derived in detail in this paper. Simulation results indicate that our proposed adaptive Network-coded-aided QAM scheme hold the potential of improving the throughput of TWR network, compared to the scheme without adaptation.