Sensing-Communication-Security Enhanced Integrated Satellite and Terrestrial Network with Active Reconfigurable Intelligent Surface

Integrated satellite and terrestrial network (ISTN), while beneficial, faces security vulnerabilities due to wireless communication's open nature, leading to potential eavesdropping and interference. This paper addresses these challenges by leveraging the characteristics of low-Earth orbit (LEO) satellites and active reconfigurable intelligent surfaces (RIS). LEO satellites' periodic coverage gaps reduce the need for continuous interference with eavesdroppers. Active RIS, capable of amplifying and optimizing reflected signals, mitigates multiplicative fading without increasing transmission power. The proposed scheme enhances the security and energy efficiency of ISTNs. An alternating optimization algorithm, based on Block Coordinate Descent (BCD) and Successive Convex Approximation (SCA), balances the active RIS's power constraints and the need for secure and efficient communication. Furthermore, the integration of Dual-Function Radar Communications (DFRC) base stations with Integrated Sensing and Communication (ISAC) capabilities improves the precision of eavesdropper detection and interference. Simulation results corroborate the effectiveness of the proposed scheme in significantly reducing the target SINR at the eavesdropper, thereby improving the secrecy gain.