An Intelligent Reflecting Surface Assisted Covert Communication System with a Cooperative Unmanned Aerial Vehicle
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摘要: 隐蔽通信可以在被监控的情况下安全传输数据,是网络安全领域重要分支。然而,实际通信系统具有通信环境复杂、覆盖范围广等特点,这使得隐蔽通信很难部署。为此,该文提出一种基于智能反射面(IRS)与无人机(UAV)辅助的无线隐蔽通信系统。引入智能反射表面作为中继节点转发发送者的信号,使用无人机作为发送者的友元节点,该友元节点通过发送人工噪声来干扰恶意用户对隐蔽通信的检测。在监听者接收噪声不确定的情况下,推导了最小错误检测概率,并与中断概率作为约束,以最大化隐蔽通信速率为目标 ,建立了系统的优化问题,采用Dinkelbach算法求解。仿真结果表明,当智能反射阵元的相位、干扰无人机的发射能量取得最优时,所提系统的隐蔽通信速率比单独配置智能反射表面的无线通信系统平均提高了37.9%,比单独配置无人机的系统评价速率提高了1.17倍。Abstract: Covert communication is considered an important branch in the field of network security, which allows for secure data transmission in monitored environments. However, challenges such as complex communication environments and wide coverage areas are encountered in practical communication systems, making the deployment of covert communication difficult. To address this issue, a wireless covert communication system assisted by Intelligent Reflective Surfaces (IRS) and Unmanned Aerial Vehicle (UAV) is proposed in this paper. In this system, IRS is introduced as relay node to forward signals from the transmitter. UAV is utilized as a friendly node for the transmitter, and artificial noise is transmitted to disrupt malicious users’ detection of covert communication. Under the condition of receiver uncertainty regarding the received noise, the minimum error detection probability is derived, and the optimization problem of the system is established with the objective of maximizing the covert communication rate while considering interruption probability as a constraint. The Dinkelbach algorithm is employed to solve the optimization problem. Simulation results demonstrate that the maximum covert communication rate can be achieved when the phase shift of the IRS elements and the UAV’s transmission power are optimized.
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1 基于SCA和Dinkelbach技术的交替优化算法
(1) 初始化,Rb,0, $ \eta $和迭代索引参数k=1; (2) 利用式(26)得到最优$ {\boldsymbol{\varTheta}} $。 (3) 重复 (4) 通过得到$ \left( {{{\boldsymbol{Q}}_{k - 1}},{\boldsymbol{\varTheta}} } \right) $,解决式(33)更新$ \left( {{P_k},{{\hat P}_{{\text{U}},k}}} \right) $; (5) 根据求出的$ \left( {{P_k},{{\hat P}_{{\text{U}},k}}} \right) $,利用式(31)更新因子$ \eta $; (6) 通过得到的$ \left( {{\boldsymbol{\varTheta}} ,{P_k},{{\hat P}_{{\text{U}},k}}} \right) $,利用式(24a)更新RB,k; (7) 设置k$ \leftarrow $k+1; (8) 直到$ \left| {{R_{B,k}} - {R_{B,k - 1}}} \right| \le \kappa $。 表 1 仿真的具体参数设置
参数 参数描述 取值 N 无人机飞行时间 30 s T 无人机飞行时隙个数 30 L 每个时隙持续时间 1 s H 无人机的固定飞行高度 50 m M 智能反射面反射单元个数 30 Vmax 无人机的最大飞行速度 50 m/s D 无人机每个时隙最大移动距离 50 m β0 信道距离为1米时的信道增益 –50 dB $ \alpha $ 路径损耗指数 2.2 D 天线间距 $ {\lambda \mathord{\left/ {\vphantom {\lambda 2}} \right. } 2} $ Pmax Alice的发射功率上限 1 W $ {\hat P_{{\text{U}},\max }} $ 无人机的最大AN功率上限 1 W $ \sigma _{\text{W}}^2 $ Willie处噪声功率方差 –120 dBm $ \sigma _{\text{B}}^2 $ Bob处噪声功率方差 –120 dBm $ \varepsilon $ Willie确定所需隐蔽性的特定值 0.01 $ \kappa $ 循环阈值 10–5 wB Bob的地面坐标(m) [–100,100]T wW Willie的地面坐标(m) [100,100]T wA 基站的地面坐标(m) [–100,0]T qA 无人机起点坐标(m) [–300,20]T qF 无人机终点坐标(m) [300,20]T -
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