Fluid Antenna In-Built Secure Joint Transmitter-Spatial and Receiver-Port Index Modulation

To address the physical layer security issues for the next generation wireless, we introduce and investigate a novel fluid antenna assisted secure joint transmitter-spatial and receiver-port index modulation (FA-SJIM) system. Specifically, we detail two schemes to enhance both the transmission efficiency and secrecy. The schemes are based on the continuous random phase and discrete random phase distortions at the transmitter and the constructive phase-aligning manipulations at the RIS, respectively. Furthermore, we derive the semi-closed-form secrecy outage probability (SOP) results of the proposed schemes with the maximum likelihood detection, so as to facilitate the evaluation of the system secrecy. Finally simulated and numerical performance results are characterized to reveal the high accuracy of SOP derivations, and the superiority of the FA-SJIM in terms of transmission efficiency and secrecy.