We aim to achieve keyless covert communication with a positive-rate in Rayleigh block-fading channels. Specifically, the transmitter and the legitimate receiver are assumed to have either causal or non-causal knowledge of the \ac{CSI} for both the legitimate and the warden channels, while the warden only knows the statistical distribution of the \ac{CSI}. Two problem formulations are considered in this work: (a) Power allocation: maximizing the sum covert rate subject to a maximum power constraint, and (b) Rate allocation: minimizing the power consumption subject to a minimum covert rate constraint. Both problems are formulated based on recent information theoretical results on covert communication over state-dependent channels. When the \ac{CSI} of each fading block is known non-causally, we propose a novel three-step method to solve both the power and rate allocation problems. In the case where the \ac{CSI} is known causally, the power allocation problem can be formulated as \ac{MDP} and be solved using a \ac{DDQN} approach. Although the rate allocation problem under causal \ac{CSI} does not directly conform to an \ac{MDP} structure, it can be approximately solved using the \ac{DDQN} trained for power allocation. Simulation results demonstrate the effectiveness of the proposed power and rate allocation methods and provide comprehensive performance comparisons across different allocation schemes.

翻译：本文旨在瑞利块衰落信道中实现无密钥的正速率隐蔽通信。具体而言，假设发射机与合法接收机对合法信道及窃听信道的信道状态信息具有因果或非因果知识，而窃听者仅知晓信道状态信息的统计分布。本文考虑两种问题建模：(a) 功率分配：在最大功率约束下最大化总隐蔽速率；(b) 速率分配：在最小隐蔽速率约束下最小化功耗。两种问题均基于近期关于状态相关信道上隐蔽通信的信息论研究成果构建。当每个衰落块的信道状态信息以非因果方式已知时，我们提出一种新颖的三步法来解决功率与速率分配问题。在信道状态信息以因果方式已知的情况下，功率分配问题可建模为马尔可夫决策过程，并采用双深度Q网络方法求解。尽管因果信道状态信息下的速率分配问题不直接符合马尔可夫决策过程结构，但可通过为功率分配训练的双深度Q网络进行近似求解。仿真结果验证了所提功率与速率分配方法的有效性，并对不同分配方案进行了全面的性能比较。