Robust RIS-aided secure NOMA-ISAC system for post-disaster management

Our paper focuses on a generalized reconfigurable intelligent surface (RIS) assisted secure non-orthogonal multiple access (NOMA) integrated sensing and communication (ISAC) system. Specifically, we analyze the combined impact of hardware impairments for transceivers at the ISAC-enabled base station, phase errors at the RIS, and aggregated distortion noise at the NOMA users. Additionally, we integrate channel estimation errors for all links into the analysis of achievable rates and secrecy performance in the proposed scheme. Furthermore, a RIS phase optimization framework is developed to maximize the achievable secrecy rate under practical hardware impairments (HWI), where particle swarm optimization (PSO), grey wolf optimization (GWO), and manifold optimization (MO) are employed and comparatively evaluated. The sensing performance of the proposed system is further characterized by deriving the sensing SINR under HWI, and the detection probability is evaluated via Monte Carlo simulation using a Swerling I target model with a constant false alarm rate (CFAR) detector. To validate our findings, we present simulations across various parameters, examining the analytical results over Rician fading channels. Moreover, the proposed RIS-assisted NOMA-ISAC architecture is intended to support resilient connectivity, situational awareness, and physical-layer security in post-disaster management scenarios, where communication infrastructures are severely damaged or unavailable.