A Cooperative Model for Enhancing Spectral Efficiency in Two-Way Amplify-and-Forward Relaying Networks

In this work, a new cooperative two-way relaying (TWR) model with amplify-and-forward (AF) protocol is proposed in which a primary user (PU) network consisting of two PU sources communicate with each other via a single relay. In addition, a secondary user (SU) source transmits its data to its SU destination via the same PU relay node. In order to mitigate SU interference caused to the PU network, the PU network considers the SU network pairs (i.e., source and destination) as two additional relay nodes helping the original PU relay node in improving the PU network performance via orthogonal space-time block code (OSTBC) technique. As a reward, the PU network allows the SU network to communicate simultaneously via the PU relay node using the decode-and-forward (DF) protocol. A power allocation optimization problem is formulated to minimize the weighted sum of the average symbol error probability of both PU and SU systems. Results show that the error performance of the proposed model outperforms the conventional TWR-AF model.