Analysis of Covert Communication in NOMA Systems: Impact of Transmit Power Distribution

In the research on covert communication, some studies have taken the perspective of the warden based on power detection and adjusted the power characteristics of the sender to reduce the probability of detection by the warden in order to realize covert communication. This letter studies the impact of transmit power distributions on the performance of covert communication in downlink NOMA communication systems. It explores the relationship between the minimum detection error probability (DEP) and the covert transmission rate, and achieves the joint optimization of the two by adjusting the power allocation parameters. The numerical results demonstrate that reducing the power allocated to the covert user effectively reduces the detection performance of the warden (Willie). Meanwhile, increasing the transmit power upper limit significantly improves the covert transmission rate. In addition, the variation of the power allocation parameters gives a tendency for the covert transmission rate to increase and then decrease, suggesting that the power allocation needs to be precisely regulated in the performance optimization.