On the Secrecy Performance of RIS-Enhanced Aerial Communication Under Imperfect CSI

In this paper, we consider the reconfigurable intelligent surface (RIS) enhanced aerial communication system, where an unmanned aerial vehicle (UAV) intends to deliver confidential information to the legitimate user in the presence of an eavesdropper with the aid of an RIS. For accurate performance analysis, we consider the practical constraints of imperfect channel state information (CSI) and discrete phase shifts for the RIS-enhanced system. Furthermore, in order to compensate for the secrecy loss due to the practical constraints, we formulate a secrecy rate maximization problem under the target secrecy rate constraint to optimize the number of RIS elements. Our extensive simulation results demonstrate the impact of various factors, namely the channel estimation error, RIS phase shift design, number of RIS elements, and transmit power, on the secrecy performance of the considered system. Moreover, the simulation results reveal that the secrecy performance degrades to a great extent in the case of imperfect channel estimation of the RIS to legitimate user's link.