能效最优准则下的无人机中继系统的功率分配算法

由于无人机（Unmanned aerial vehicle，UAV）机动性好且部署简单，基于无人机中继的传输技术受到了广泛关注。功率作为通信系统的重要资源，其分配问题直接影响各条链路的性能和整个通信系统的能量效率。本文以莱斯衰落信道为背景，提出了一种在系统能效准则下的无人机中继通信系统的功率分配算法。首先在双跳放大转发（Amplify-and-forward，AF）中继传输模型的基础上建立功率分配的优化模型，将功率分配问题转化为求解最大系统能效的优化问题。在最优功率分配的求解过程中，先固定发射信号功率，获得波束形成优化方案；然后通过大信噪比区间近似，将非凸优化问题转化为凸优化问题；最后利用KKT（Karush-Kuhn-Tucker）条件，计算得出功率分配方案的闭式解。仿真实验表明，本文算法相对于迭代算法降低了算法复杂度。

Optimal Energy Efficiency Based Power Allocation Algorithm for UAV Relay Communication System

Since the unmanned aerial vehicle (UAV) has high maneuverability and simple deployment, the UAV-based transmission technology has received much attention. As an important resource of the communication system, power allocation will affect the each link performance and the energy efficiency. In this paper, taking the energy efficiency as a criterion, a power allocation algorithm is proposed for UAV relay communication system under rician fading channel. First, the problem of power allocation is formulated as an optimization model for amplify-and-forward (AF) relay transmission model. Then the beamforming optimization scheme is obtained with the fixed transmission power. Next, the original non-convex optimization problem is transformed into convex optimization problem through large signal to noise ratio interval approximation. Finally, Karush-Kuhn-Tucker (KKT) condition is used to calculate the closed form of the optimal power allocation. Simulation results show that the performance of proposed algorithm is very close to that of the iterative method. But the computational complexity is lower. Compared with the average algorithm, the proposed algorithm has more larger energy efficiency which can lead to system performance improvement.