Encoded Jamming Secure Communication for RIS-Assisted Systems

This paper investigates a cooperative jamming (CJ)-aided secure wireless communication system. Conventional CJ schemes transmit Gaussian noise (GN) to improve security, which inherently degrades the legitimate receiver's performance. While the encoded jamming (EJ) scheme mitigates this interference, its advantage over the GN scheme is highly channel-dependent. To address this limitation, we introduce a reconfigurable intelligent surface (RIS)-assisted secure design based on the EJ scheme for secrecy-rate maximization. Starting from the multiple-input multiple-output (MIMO) secrecy-rate expressions for the EJ and GN schemes, we identify the jamming-channel conditions under which the EJ scheme may be limited. For the general MIMO setup, we develop a weighted minimum mean-square error (WMMSE)-based framework for joint precoder and RIS phase optimization. We further provide a large-RIS asymptotic benchmark showing that a jamming-aligned EJ construction achieves a positive gap over a signal-aligned GN benchmark in the considered multiple-input single-output (MISO) setting. Simulation results support the analysis and show that, under the evaluated settings, the RIS-assisted EJ scheme can alleviate the identified spatial bottlenecks and improve the secrecy rate relative to the considered baselines.