Covert communications for AAV aided multi-antenna STAR-RIS-NOMA systems with imperfect CSI

This study investigates covert communication for a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-assisted multi-antenna non-orthogonal multiple access (NOMA) system in the context of imperfect channel state information (CSI). In this setup, a source transmits a NOMA signal with both public and covert information to an autonomous aerial vehicle relay, which then forwards it to both covert and public users via a direct link as well as the reflected or transmitted one from the STAR-RIS in the presence of multiple wardens attempting to detect whether the covert information being transmitted or not. Considering imperfect CSI scenario, analytical expressions for the detection error probability at the warden are derived and validated through Monte-Carlo simulations in the presence of two typical detection scenarios. Furthermore, the optimal detection threshold and the maximum effective covert rate are also investigated and discussed.