BackCom-Aided NOMA Systems: A Simultaneous Process of Covertness and Information at Tag

In this letter, we achieve a simultaneous process of covertness and information by using the backscatter node (Tag) in uplink non-orthogonal multiple access (NOMA) systems. To reach this goal, we employ the best antenna pair scheme for decoding and formulate the multiobjective optimization problem for both the covert user’s effective covertness rate and Tag’s effective transmission rate. As a result, Tag is capable of both transmitting information and performing a covertness function. Adopting Tag for covertness presents outstanding performance in comparison to using an energy harvesting jammer. Under the Tag scheme, the use of a large number of antennas for legal decoding is an efficient way to enhance covertness performance. In addition, the public user plays an active role in covert communications by increasing the transmit power in a controlled manner.