AI 中文总结
本文针对具备几何感知能力的看守者，提出保留用户到看守者大尺度衰落系数的隐蔽通信框架，推导了检测错误概率等关键指标，开发了低复杂度功率控制算法，验证了空间分散度等因素对协作用户数量的影响。
AI 中文摘要
本文研究隐蔽通信问题，其中单个隐蔽用户得到多个空间分布的非隐蔽用户协助，以对抗具备几何感知能力的看守者。与现有基于以接收机为中心的激活、同质信道或平均几何的工作不同，所提框架在协作用户激活和看守者检测分析中保留了各用户到看守者的大尺度衰落系数。在所采用的大规模用户部署分析框架下，我们建立了一种开-关激活结构，该结构可平衡对Bob（合法接收者）造成的干扰以及对看守者的干扰效果。基于得到的聚合干扰统计量，我们推导了检测错误概率的闭式近似、使该概率最小的检测阈值，以及满足隐蔽约束所需的最小协作用户数量。随后，我们将原始高维功率控制问题简化为一维分段搜索，并开发了一种避免依赖分辨率的网格搜索的低复杂度算法。分析表明，看守者侧更大的空间分散度可减少所需的协作用户数量，而用户到看守者的平均距离更大则会增加所需数量。数值结果验证了分析结论，显示有限样本检测方法趋近于大样本基准，而不完美的用户到Bob信道估计主要通过激活误差降低可达速率。
英文摘要
This paper investigates covert communication in which a single covert user is assisted by multiple spatially distributed non-covert users against a geometry-aware warden. Unlike prior works based on receiver-centric activation, homogeneous channels, or averaged geometry, the proposed framework retains the individual user-to-warden large-scale fading coefficients in both cooperative user activation and the warden's detection analysis. Under the adopted analytical formulation for large-scale user deployments, we establish an on--off activation structure that balances the interference caused at Bob and the interference effectiveness at warden. Based on the resulting aggregate-interference statistics, we derive a closed-form approximation of the detection error probability, the detection threshold that minimizes it, and the minimum number of cooperative users required to satisfy the covert constraint. Then, we reduce the original high-dimensional power-control problem to a one-dimensional piecewise search and develop a low-complexity algorithm that avoids resolution-dependent grid search. The analysis shows that greater warden-side spatial dispersion can reduce the required cooperative users, whereas a larger average user-to-warden distance increases it. Numerical results validate the analysis and show that finite-sample detection approaches the large-sample benchmark, while imperfect user-to-Bob channel estimation mainly reduces the achievable rate through activation errors.
Comments13 pages, 5 figures
