Covert communication prevents legitimate transmission from being detected by a warden while maintaining certain covert rate at the intended user. Prior works have considered the design of covert communication over conventional low-frequency bands, but few works so far have explored the higher-frequency millimeter-wave (mmWave) spectrum. The directional nature of mmWave communication makes it attractive for covert transmission. However, how to establish such directional link in a covert manner in the first place remains as a significant challenge. In this paper, we consider a covert mmWave communication system, where legitimate parties Alice and Bob adopt beam training approach for directional link establishment. Accounting for the training overhead, we develop a new design framework that jointly optimizes beam training duration, training power and data transmission power to maximize the effective throughput of Alice-Bob link while ensuring the covertness constraint at warden Willie is met. We further propose a dual-decomposition successive convex approximation algorithm to solve the problem efficiently. Numerical studies demonstrate interesting tradeoff among the key design parameters considered and also the necessity of joint design of beam training and data transmission for covert mmWave communication.

中文翻译：

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隐蔽毫米波通信的联合波束训练和数据传输设计

隐蔽通信防止合法传输被管理员检测到，同时在预期用户处保持一定的隐蔽速率。先前的工作已经考虑了在传统低频段上进行隐蔽通信的设计，但迄今为止很少有工作探索更高频率的毫米波 (mmWave) 频谱。毫米波通信的定向特性使其对隐蔽传输具有吸引力。然而，如何以隐蔽的方式首先建立这种定向链接仍然是一个重大挑战。在本文中，我们考虑了一个隐蔽的毫米波通信系统，其中合法方 Alice 和 Bob 采用波束训练方法进行定向链路建立。考虑到训练开销，我们开发了一个新的设计框架，共同优化波束训练持续时间，训练功率和数据传输功率，以最大化 Alice-Bob 链路的有效吞吐量，同时确保满足守望者 Willie 的隐蔽性约束。我们进一步提出了一种双分解逐次凸逼近算法来有效地解决这个问题。数值研究表明，在考虑的关键设计参数之间进行了有趣的权衡，也证明了联合设计波束训练和数据传输用于隐蔽毫米波通信的必要性。