基于射频能量收集的无人机协助的分时段功率分配策略

针对毫微微基站（FBS）在不同时间段用户数量的差异，研究了最大化下行总信息量的功率分配问题.不同时间段包含忙时和闲时2个阶段，忙时用户数量较多，闲时用户数量较少.通过部署一个无人机携带的微微基站（PBS-UAV）为多个FBSs闲时的用户提供服务.FBS和PBS-UAV都具有能量收集功能.在FBS忙时，FBS和PBS-UAV同时从宏基站收集能量，并且向用户发送数据.FBS闲时，由PBS-UAV接替多个FBSs，与用户进行下行通信.将功率分配问题建模为最优化问题，以最大化FBS和PBS-UAV的下行信息量为目标，同时满足FBS和PBS-UAV能量消耗及发射功率的约束条件.由于建立的最优化问题是凸优化问题，可通过引入增广拉格朗日乘子法获得最优解.仿真结果表明，与PBS-UAV参与的等功率及部分功率固定的方法相比，所提出的方法在总信息量方面有不同程度的增加.

UAV-Assisted Time Division Power Allocation Strategy Based on RF Energy Harvesting

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.