Energy-Efficient Cooperation in Cognitive Wireless Powered Networks

In this letter, we consider a cooperative sharing model for cognitive wireless powered communication networks (CWPCNs), which leverages the notion of cooperation between primary and secondary systems in cognitive radio networks to accomplish primary transmission early and vacate opportunity for secondary transmission. With the proposed spectrum sharing model, we investigate the optimal design for such a cooperative CWPCN with both amplify-and-forward (AF) and decode-and-forward (DF) protocols to maximize its uplink energy efficiency. The energy efficiency optimization problem is decomposed into two subproblems for uplink scheduling and cooperative power control. We also propose a suboptimal solution to tackle the unavailable information on channel condition between the primary transmitter and secondary users. The numerical results show that the DF protocol outperforms the AF protocol in general and the suboptimal solution is slightly outperformed by the optimal one.