Sensing-Assisted Secure Communication With Beam Hopping for LEO-ISAC Satellite Systems

To address the secure downlink communication problem of communication-sensing collaboration in low earth orbit beam hopping integrated sensing and communication (LEO-BH-ISAC) satellite systems, we propose the concept of credible communication and sensing airspace (CCSA). Specifically, CCSA is defined as the intersection of credible communication airspace (CCA), which guarantees secure communication for legitimate users, and credible sensing airspace (CSA), in which eavesdroppers are effectively intercepted. To maximize the CCSA, an optimally balanced beam configuration and power allocation model is established to quantify the relationship between satellite resources and the CCSA. Subsequently, a staged multi-dimensional resource allocation algorithm is proposed, which first accomplishes beam pre-configuration and time slot allocation, and then realizes dynamic power allocation between communication and sensing beams via alternating iterative optimization. Simulation results demonstrate that this method can meet the differentiated throughput requirements of all cells. Meanwhile, compared with the average power scheme, the CCSA is improved by 16.5% on average, and both the secrecy rate and the interception probability approach their theoretical values. Furthermore, the CCSA can be expanded by increasing the power of communication and sensing beams and reducing the secrecy rate threshold. This work validates the effectiveness of the CCSA, providing new ideas for communication-sensing collaboration in LEO-BH-ISAC satellite systems.