Abstract: Aiming at the difference of users in different time periods for the femto base station (FBS),the power allocation problem of maximizing the total downlink information is investigated.The different time periods include busy time and spare time.There are more users in the busy time and less users in the spare time.By deploying a pico base station carried by unmanned aerial vehicle (PBS-UAV),it provides services for users of multiple FBSs in spare time.Both the FBS and PBS-UAV have energy harvesting function.During the busy time,the FBS and PBS-UAV simultaneously harvest energy from the macro base station,and FBSs transmit data to users.During the spare time,multiple FBSs are replaced by the PBS-UAV to communicate with users in downlink.The power allocation problem is modeled as an optimization problem.The objective is to maximize the amount of downlink information of FBSs and PBS-UAV while satisfying the constraints of FBS and PBS-UAV energy consumption and transmission power.Because the formulated optimization problem is a convex optimization problem,the optimal solution is obtained by using an augmented Lagrange multiplier method.Simulations show that compared with the equal power method and partial fixed power method with PBS-UAV,the proposed method has an increase in terms of total information to different degrees.

Key words: energy harvesting, power allocation, unmanned aerial vehicle