无人机网络中人工噪声增强的短包隐蔽通信

考虑无人机（Unmanned Aerial Vehicle， UAV）网络中人工噪声（Artificial Noise， AN）增强的隐蔽无线通信，其中UAV工作在全双工状态，不仅接收Alice发送的隐蔽信息，而且产生AN恶化Willie的探测性能。构建了UAV的三维位置部署和AN发射功率以及Alice发射功率设计的联合优化问题。所构建的优化问题是非凸的且其优化变量相互耦合，这导致该优化问题很难直接求解。为了求解该优化问题，首先根据优化问题隐含的特性，将其等价地转换为更易处理的形式。随后，推导了Alice发射功率和AN发射功率的最优解析表达式。随后证明了UAV的最优水平位置一定位于Alice和Willie的连线上。在此基础上，推导了UAV的最优三维放置位置。仿真结果表明，与无AN方案相比，所提方案可以显著的提高系统的隐蔽传输性能。 

Artificial Noise Enhanced Short-Packet Covert Communications for UAV Networks

? ?This work we consider an artificial noise （AN） enhanced unmanned aerial vehicle （UAV） covert communications， where the UAV working in full-duplex mode not only receives covert information transmitted by Alice， but also generates AN to degrade Willie’s detection. We formulate an optimization problem of the UAV’s three-dimensional （3D） placement and UAV’s AN transmit power together with Alice’s transmit power. The formulated optimization problem is non-convex and the involved optimization variables are coupled each other closely， which makes it difficult to solve the optimization problem directly. To overcome this difficulty， we first equivalently transform it into a more tractable form according to the implicit characteristics of the optimization problem. Then， we derive analytical expressions for Alice’s transmit power and UAV’s AN transmit power. We next prove that the UAV’s optimal horizontal location must lie on the straight line connecting the Alice and Willie， based on which we derive the UAV’s optimal 3D location. Our simulation results show that the proposed AN scheme can obtain a significant covert transmission performance gain compared with the scheme without AN.