Covert Non-Orthogonal Multiple Access Communication Assisted by Multi-Antenna Jamming

As the Internet of Things (IoT) becomes increasingly popular, the amount of information transmitted through the IoT network has increased significantly. Therefore, the privacy and security problem of the transmitted information has become a major area of focus. Motivated by this, this paper considers the covert communication based on non-orthogonal multiple access (NOMA), which consists of a transmitter, a legal user, a warden with power detection function and a multi-antenna jammer. To realize the covert communication between the transmitter and the legitimate user, the detection error probability of the warden is firstly derived, and then the optimal detection threshold and the minimum detection error probability (MDEP) are obtained. In addition, with the aim of designing this system, the average MDEP of the warden is calculated, and the closed form solution for the outage probability (OP) of the communication link is obtained. Then, a scheme is proposed to optimize the covertness of this system under the covertness constraint and interruption constraint, through which the maximum covert throughput of the system can be obtained. The simulated numerical results validate the theoretical analysis, and testify that: i) the detection performance of the warden can be reduced by increasing the maximum jamming power of the jammer or reducing the transmitting power of the transmitter; ii) by optimizing the power allocation factor, the maximum covert throughput of the system can be obtained under the premise of satisfying the covertness constraint and interruption condition; iii) the proposed optimization scheme can enhance the covertness performance of this system.