This work investigates the phase gain of intelligent reflecting surface (IRS) covert communication over complex-valued additive white Gaussian noise (AWGN) channels. The transmitter Alice intends to transmit covert messages to the legitimate receiver Bob via reflecting the broadcast signals from a radio frequency (RF) source, while rendering the adversary Willie's detector arbitrarily close to ineffective. Our analyses show that, compared to the covert capacity for classical AWGN channels, we can achieve a covertness gain of value 2 by leveraging Willie's uncertainty of phase angles. This covertness gain is achieved when the number of possible phase angle pairs $N=2$. More interestingly, our results show that the covertness gain will not further increase with $N$ as long as $N \ge 2$, even if it approaches infinity.

翻译：本工作研究智能反射面（IRS）在复值加性高斯白噪声（AWGN）信道中实现隐蔽通信的相位增益。发射方Alice旨在通过反射射频（RF）源的广播信号，将隐蔽信息传输给合法接收方Bob，同时使敌手Willie的检测器任意趋近于无效。分析表明，与经典AWGN信道的隐蔽容量相比，通过利用Willie对相位角的不确定性，我们能够获得值为2的隐蔽增益。这一隐蔽增益在可能的相位角对数N=2时实现。更有趣的是，我们的结果表明，当N≥2时，即使N趋近于无穷大，隐蔽增益也不会随N进一步增加。