Energy-Efficient Power Control for Cognitive Satellite-Terrestrial Networks With Outdated CSI

Taking account of the limited energy and large feedback delay in satellite communications, in this article, we propose an energy-efficient power control scheme for cognitive satellite-terrestrial networks with outdated channel state information (CSI), where satellite network reuses the spectrum resources of terrestrial networks. Specifically, to guarantee reliable communications for both networks, we first formulate the power control scheme as an energy efficiency (EE) maximization problem subjected to interference power constraints imposed by terrestrial communications and rate constraints of satellite communications. Moreover, we solve the nonlinear concave optimization problem and derive the average transmit power for theoretical performance evaluation. Simulation results reveal the impacts of various key parameters on satellite communications.