An Energy-efficient Adaptive Spectrum Sharing Scheme For Full Duplex Cognitive Radios

In traditional cognitive radio networks, the spectrum sharing schemes are spectrum-efficient in specific circumstances. In order to improve the robustness of spectrum sharing schemes in a dynamic environment from the perspective of energy efficiency, an adaptive spectrum sharing scheme is proposed for full duplex cognitive radios in this work. The proposed schemes allow secondary users (SUs) to adapt their way of accessing the licensed spectrum according to the behaviors of primary users (PUs). The SUs adaptively decide to access the licensed spectrum in the transmit phase, provided that PUs' traffic arrives at a low rate and energy efficiency gains exist. Based on the intermittent nature of the arrival and departure processes of PUs' traffic, the closed-form expressions of energy efficiency for the traditional and the proposed schemes are investigated. By defining energy efficiency gain and energy efficiency loss, the impacts of the spectrum sensing error and channel estimation error are analyzed to evaluate the energy efficiency of the proposed scheme. It shows that the proposed adaptive spectrum sharing scheme improves the overall energy efficiency. The numerical results validate the energy efficiency improvements and the robustness of the proposed scheme.