Joint secure beamforming and sensing strategy for ISAC-enabled LEO satellite system

Abstract

In the aspect of enhancing the spectrum and hardware efficiency in satellite communications, Integrated Sensing and Communication (ISAC) plays a vital role. However, the open nature of the wireless channel makes satellite communication networks extremely vulnerable to eavesdropping. In this paper, we propose a Physical Layer Security (PLS) strategy in the ISAC Low Earth Orbit (LEO) satellite system, which guarantees the communication safety and position privacy simultaneously. In the ISAC LEO satellite system, the targets are regarded as potential Eavesdroppers (Eves), and these Eves may eavesdrop on the information transmitted by the communication transmitter to the legitimate users. To guarantee the secrecy of the transmission, Artificial Noise (AN) is introduced at the transmitter. Then, we respectively formulate the communication and sensing channel models of the ISAC LEO satellite system and thereby deduce the expressions of the secrecy rate. Meanwhile, considering the extreme difficulty in obtaining information at Eves, the Cram$\acute{e}$r-Rao Bound (CRB) is adopted to characterize the evaluation of the estimation accuracy of Eves. To explore the optimal trade-off between the sensing performance and the secrecy rate of the system, we propose a normalized weighted optimization strategy to maximize the secrecy rate and minimizing the CRB of Eves’ estimation simultaneously. The numerical results validate the performance improvement of the proposed scheme with respect to the security of ISAC-enabled LEO satellite system.