Abstract:

Aiming at the problems of energy limitation and secure communication of Unmanned Aerial Vehicle （UAV） communication， by jointly optimizing the transmitting power and flight trajectory of UAV， and aiming at the maximization of average secrecy capacity of the system， a security scheme of mobile edge computing system based on UAV Wireless Power Transfer （WPT） was proposed. In this scheme， due to the non-smooth nature of the objective function， it is difficult to solve directly. To solve the above problems， firstly， the non-smooth objective function was reconstructed into an equivalent smooth objective function. Then， the reconstructed objective function was decoupled into two sub-problems， namely， optimizing the transmitting power for a given flight trajectory and optimizing the flight trajectory for a given transmitting power. And the optimal solutions of the two sub-problems were solved using the two-dimensional binary search method and the successive convex approximation algorithm respectively. Finally， the suboptimal solution of the problem was found through the block coordinate descent method， and the two sub-problems were solved iteratively and alternately. The results of comparing the proposed scheme with the trajectory optimization scheme without transmitting power control， the optimal trajectory optimization scheme with transmitting power control， and the optimal trajectory optimization scheme without transmitting power control show that： as the flight time increases， the average secrecy rate of the proposed scheme is increased by 36.0%， 9.2%， and 34.8%， respectively； as the transmitting power increases， the average secrecy rate of the proposed scheme is increased by 12.4%， 3.0%， and 14.4%， respectively. So the proposed scheme can effectively improve the average secrecy rate of the system.

Key words: Unmanned Aerial Vehicle (UAV) communication, Physical Layer Security (PLS), secrecy rate, Wireless Power Transfer (WPT)

摘要：

针对无人机（UAV）通信的能量受限和安全通信问题，通过联合优化UAV的发射功率和飞行轨迹，以最大化系统平均保密容量为目标，提出一个基于UAV无线能量传输（WPT）的移动边缘计算系统安全方案。但该方案的目标函数是非光滑的，难以直接求解。为了解决上述难题，首先，将非光滑的目标函数重构为等价的光滑目标函数；其次，将重构的目标函数解耦为给定飞行轨迹优化发射功率和给定发射功率优化飞行轨迹两个子问题，并分别通过二维二分搜索法和连续凸逼近法求解这两个子问题的最优解；最后，通过块坐标下降法找到问题的次优解，并以迭代的方式交替求解两个子问题。与无发射功率控制的轨迹优化方案、发射功率控制的最佳轨迹优化方案以及无发射功率控制的最佳轨迹优化方案进行对比的实验结果表明：随着飞行时间的增长，所提方案的平均保密率分别增加了36.0%、9.2%和34.8%；随着发射功率的增大，所提方案的平均保密率分别增加了12.4%、3.0%和14.4%。所提方案能有效提高系统的平均保密率。

关键词: 无人机通信, 物理层安全, 保密率, 无线能量传输