Security-Reliability Tradeoff in UAV-Carried Active RIS-Assisted Cooperative Networks

In this letter, we propose an unmanned aerial vehicle (UAV)-carried active reconfigurable intelligent surface (RIS)-assisted cooperative network (UARCN) with a source (S), a trustworthy user (U), and an untrustworthy user (E), which is bridged by multiple half-duplex decode-and-forward relays and an active RIS mounted on a hovering UAV. In the UARCN, both U, E, and relays receive the signal from S through the active RIS merely in the first time slot; then one out of the successful decoding relays is selected to further transmit information via the direct link and RIS in the second time slot. The outage probability and intercept probability are jointly analyzed to investigate the security and reliability tradeoff (SRT) of the system. Simulation results validate our theoretical analysis, revealing that the active RIS can bring greater improvement to the system SRT than passive or hybrid RIS, and its location can be further optimized.