Joint Power Control and Time Allocation for Wireless Powered Underlay Cognitive Radio Networks

This letter considers a wireless powered underlay cognitive radio network where secondary users (SUs) first harvest energy in the downlink wireless power transfer (WPT) phase and then use the energy for data transmission in the uplink wireless information transmission phase adopting the time-division multiple access. Our aim is to maximize the sum rate of the SUs under the interference power constraint enforced by the primary user and the transmit power constraints. The optimal joint power control for the WPT phase and time allocation among the SUs is obtained. Simulation results show that the obtained optimal scheme outperforms the scheme that employs only the optimal time allocation or the optimal power control.