无人机（unmanned aerial vehicles,UAVs）凭借高机动性与快速部署能力，可在复杂军事对抗区域通过中继辅助方式显著扩展隐蔽通信的覆盖范围。然而，传统无人机中继辅助隐蔽通信受隐蔽性约束影响，导致长距离通信速率较低。为解决该问题，本文提出一种双无人机双辅助隐蔽通信的位置优化方法。该方法在利用一架无人机作为中继辅助设备进行隐蔽信号转发的同时，引入另一架无人机作为友好干扰辅助设备以提高检测方的不确定性。具体地，首先构建双无人机双辅助隐蔽通信模型，分析该模型下检测方的检测错误概率，并推导隐蔽性约束条件；然后采用块坐标下降（block coordinate descent,BCD）法，在隐蔽性约束和发射功率约束下联合优化干扰无人机和中继无人机的位置，最大限度地提高系统的隐蔽传输速率。仿真结果表明，相较于现有方法，所提方法能够显著提高隐蔽传输速率。
Due to their high mobility and rapid deployment, unmanned aerial vehicles (UAVs) can significantly expand the coverage of covert communication by relay-assisted methods in complex military confrontation areas. However, traditional UAV relay-assisted covert communication suffers from low transmission rates over long distances due to covert constraints. To this end, this paper proposed a position optimization method for dual-UAV double-assisted covert communication. While employing one UAV as a relay to forward covert signals, this method introduces an additional UAV as a friendly jammer to increase the uncertainty at the detector. Specifically, a dual-UAV double-assisted covert communication model was built, the detection error probability of the detector under this model was analyzed, and the covert constraint was derived. Then, the block coordinate descent (BCD)method was employed to jointly optimize the positions of the jamming UAV and the relay UAV under covert and transmission power constraints, aiming to maximize the system’s covert transmission rate. Simulation results demonstrate that the proposed method can significantly improve the covert transmission rate compared to existing methods.
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