Cooperative spectrum sharing-based relaying protocols with wireless energy harvesting cognitive user

In this study, the authors consider an energy-constrained secondary user which harvests energy from the primary signal and forwards this latter with the guarantee of spectrum access. Two key protocols are proposed, namely time-splitting cooperative spectrum sharing (TS-CSS) and power-sharing cooperative spectrum sharing (PS-CSS), based on time splitting and power sharing at the relay, respectively. Assuming a Nakagami-m fading model, exact closed-form expressions for the outage probabilities of the primary and secondary users are derived in decode-and-forward and amplify-and-forward relaying modes. From the obtained results, it is shown that the secondary user can carry its own transmission without any adverse impact on the performance of the primary user and that the PS-CSS protocol outperforms the TS-PSS protocol in terms of outage probability over a wide range of signal-to-noise ratio. Furthermore, the effect of various system parameters, such as splitting ratio, distance between nodes and harvesting efficiency, on the system outage performance on employing the proposed protocols is investigated and several insights are drawn.