Research on Fundamental Performance Limit of Covert Visible Light Communications

Facing the development needs of the sixth-generation mobile communication, Visible Light Communication (VLC) is a promising indoor coverage candidate. Due to the open and broadcast features, the information security of VLC can not be ignored. As a novel information security technology, covert wireless communication has been widely investigated in recent years. However, there are significant differences between VLC and radio frequency wireless communication. The results of covert wireless communication can not be directly applied to covert VLC. In view of this, the basic theory of covert VLC is studied in this paper. First, under the constraints of covertness, nonnegativity and average optical power, a functional optimization problem is established. The optimal input distribution is obtained as an exponential distribution, which provides a reference for the signal design of covert VLC. Using the covertness constraint, the condition which should be satisfied by the transmitter's average optical power is obtained, it provides a basis for the transmitter to set the transmit power. Then, when the transmitter has or has not the knowledge of the warden's information, the maximum amounts of information that can be covertly transmitted by covert VLC are derived, which reveals the fundamental performance limit of covert VLC. Finally, numerical results verify the theoretical analysis.