Secrecy performance of hybrid satellite-terrestrial relay networks in the presence of multiple eavesdroppers

This study investigates the secrecy performance of a hybrid satellite-terrestrial relay network (HSTRN) in the presence of multiple eavesdroppers, where the satellite link undergoes Shadowed-Rician fading, while the terrestrial link follows Rayleigh fading. The authors suppose the direct link between the satellite and the intended user is unavailable due to heavy shadowing and adopt a multi-antenna relay using either a decode-and-forward (DF) or an amplify-and-forward (AF) protocol to assist the transmission. By employing perfect channel state information of each link at the relay, the authors first apply receive maximal ratio combining beamforming (BF) and transmit zero-forcing BF schemes to obtain the output signal-to-noise ratios (SNRs) of the intended user and eavesdroppers. Then, based on the Meijer-G function and the moment generating function, the authors derive the analytical expressions of the ergodic secrecy rate for the considered HSTRN for both DF and AF protocols. Finally, Monte-Carlo simulations are conducted to validate the theoretical performance analysis and reveal the effects of certain representative parameters on the system secrecy performance.