Energy Efficiency Optimization of IRS-Assisted UAV Networks Based on Statistical Channels

In this letter, intelligent reflecting surface (IRS) is adopted to assist unmanned aerial vehicle (UAV) to achieve energy-efficient transmission. Specifically, the energy efficiency is maximized by jointly optimizing the UAV trajectory, transmit power and IRS phase shifts based on the statistical channel state information (CSI), since the instantaneous CSI is difficult to obtain due to the mobility of UAV and the passive structure of IRS. The non-convex problem is decomposed into two sub-problems of the trajectory and transmit power optimization, and the phase-shift optimization. To deal with the non-convexity of the first one, the successive convex approximation and Dinkelbach's algorithm are utilized. For the second one, a closed-form solution is derived directly through equivalent transformations. Then, the two sub-problems are solved iteratively to obtain an effective solution to the original problem. Simulation results are presented to validate the effectiveness of the proposed scheme.