Spectrum Sensing Optimization in an UAV-Based Cognitive Radio.

In cognitive radio (CR), the detection performance of traditional spectrum sensing may be decreased due to the multipath fading and shadowing effect. However, unmanned aerial vehicle (UAV) can receive a higher strength signal without suffering severe fading and shadowing. In this paper, an UAVbased CR is proposed to improve spectrum sensing performance and access the idle spectrum. The UAV performs circular flight with the PU locating at the center, and the flight period is divided into sensing radian and transmission radian. Only when the absence of the PU has been detected within sensing radian can the UAV access the spectrum. The spectrum sensing optimization is formulated as an optimization problem, which seeks to maximize the effective throughput of the UAV by optimizing the sensing radian subject to the constraint of the interference throughput. Then, virtual cooperative spectrum sensing is proposed to improve sensing performance in fading channel, and the effective throughput is maximized by jointly optimizing local sensing radian and the number of sensing slots. The simulation results show that better UAV transmission performance can be obtained by optimizing spectrum sensing, and the virtual cooperative spectrum sensing outperforms the single spectrum sensing especially in deep fading channel.