Detection Threshold Optimization for RF-powered Full-duplex Cognitive Radio Networks

In RF-powered full-duplex cognitive radio networks (FD CRNs), with the help of FD technique and energy harvesting capability, secondary users (SUs) can conduct spectrum sensing, utilize the spectrum opportunistically and harvest energy from RF signals simultaneously. Since the circumstances whether secondary transmitters (STs) are transmitting or not are different, two detection thresholds for energy detector are employed. In this paper, we investigate the problem of optimizing detection thresholds to maximize both energy efficiency (EE) and harvesting efficiency (HE) in RF-powered FD CRNs under the constraint that the primary user (PU) is protected. We define a new objective function, i.e., the weighted sum of EE and HE and formulate the optimization problem mathematically. Further we optimize the defined objective function and obtain the optimal detection thresholds and the corresponding EE and HE. Simulation results are given to verify the proposed optimization scheme and the theoretical analyses.