Full-Duplex Based Spectrum Sharing in Cognitive Two-Way Relay Networks

Considering that full-duplex relaying (FDR) can achieve higher spectral efficiency than traditional half-duplex relaying (HDR), a spectrum sharing protocol based on FDR is proposed in this paper. We investigate a two-phase FDR spectrum sharing protocol in cognitive two-way relay networks. Analytical expressions for the outage probabilities of the primary and secondary systems under the proposed protocol are derived in a closed form. Monte-Carlo simulations are carried out to confirm the analytical expressions. Results show that the performance of our two-way FDR spectrum sharing protocol depends on the residual loop interference (LI) at the relay node. When the residual LI is small, the proposed FDR spectrum sharing protocol can significantly improve the outage performance. Furthermore, if the residual LI is small enough, the two-way FDR spectrum sharing scheme can outperform its HDR counterpart, both for the primary system and the secondary system.