Cognitive spectrum sharing with two-way relaying systems

Dynamic spectrum-sharing protocols are gaining attention due to the need for improved spectrum utilization. We propose a spectrum-sharing protocol with two-way relaying systems, where two licensed primary users A and B communicate with each other with the assistance of an unlicensed secondary transceiver C, which acts as a relay. The secondary transceiver C gains spectrum sharing by using a decode-and-forward (DF) relay protocol and superposing the secondary transmission on network-coded primary signals. We analytically derive the outage probabilities for both the primary and secondary systems under the proposed cognitive two-way relaying (CTR) protocol. Our results show that a spectrum-sharing region exists such that, as long as C is located within this region, there will be a power-allocation threshold above which the proposed CTR protocol is able to provide a better (or an equal) outage performance for the primary system and, at the same time, achieve secondary spectrum sharing.