有源RIS辅助的半免授权NOMA上行系统安全传输方案OA

To address secure uplink transmission in active reconfigurable intelligent surface(ARIS)-assisted semi-grant-free non-orthogonal multiple access(SGF-NOMA)systems under time-varying channels and eavesdropping channel un-certainty,a secure resource allocation scheme was proposed.First,the amplitude amplification and phase control capa-bilities of ARIS were exploited to compensate for cascaded path loss.The base station receive beamforming,ARIS amplitude-and-phase coefficients,and grant-free user transmit powers were jointly optimized to maximize the long-term secrecy rate.Then,a multi-agent twin delayed deep deterministic policy gradient algorithm based on centralized training with decentralized execution was developed to enable cooperative secure decision-making between the base station and grant-free users.By incorporating twin critic networks,target policy smoothing,and delayed policy updates,the pro-posed algorithm mitigated policy oscillations caused by channel dynamics and eavesdropping channel estimation errors,thereby improving training stability and real-time decision-making capability.Simulation results show that the proposed scheme improves the system secrecy rate by approximately 46％compared with the passive RIS-assisted SGF-NOMA scheme and achieves superior secrecy performance under time-varying and uncertain channel conditions.