Sum Rate Maximization for Self-Sustainable IRS-Assisted UAV Communications

In this letter, we propose a novel time switching (TS) transmission scheme for intelligent reflecting surface (IRS)-assisted unmanned aerial vehicle (UAV)-enabled wireless powered communication network (WPCN). In the energy harvesting (EH) phase, the operation of IRS is switched between energy harvesting and reflecting to improve the energy transfer. In the information transmitting (IT) phase, the operation of IRS is switched between assisted and unassisted IT to avoid the deficient duration of IT phase when the IRS is energy starved. We formulate an achievable sum-rate maximization problem by jointly optimizing the resource allocation, IRS phase shift and location of the UAV. To address the non-convexity resulting from coupling of variables, we divide original problem into three sub-problems and solve them with the block coordinate descent (BCD) method. The numerical results testify that the proposed scheme can obtain the significant sum-rate gain compared to the traditional TS scheme.