Physical-Layer Security for Friendly Jammers Assisted Satellite–Terrestrial Integrated Networks

This article investigates the physical-layer security (PLS) of a satellite-terrestrial integrated network (STIN) consisting of a satellite (S), a destination (D), and several friendly jammers in the presence of an eavesdropper (E). For improving PLS of the STIN, we propose three friendly jammer assisted communication schemes to help S securely send confidential information to D, i.e., the random jammer selection assisted communication (RJSC) scheme, the optimal jammer selection assisted communication (OJSC) scheme, and the multiple jammers assisted communication (MJC) scheme. For performance comparison, the nonjammer assisted communication (NJC) scheme is also presented. We analyze secrecy performance of the NJC, RJSC, OJSC, and MJC schemes by carrying out their closed-form secrecy outage probability (SOP) expressions, respectively. Numerical results unveil that the RJSC, OJSC, and MJC schemes exceed the NJC scheme with regard to their SOPs (e.g., as shown in <xref ref-type="fig" rid="fig2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fig. 2</xref>, when the signal-to-noise ratio is 25 dB, SOP of the STIN drops from 70% to 3%), and the OJSC scheme can get the best secrecy performance, showing the secrecy benefits of adopting friendly jammers assisted communication schemes against eavesdropping. Additionally, by increasing the number of friendly jammers, the secrecy performance of the OJSC and MJC schemes can be significantly enhanced, while that of the RJSC scheme remains unchanged.