Hybrid Satellite-Terrestrial Relaying Networks With Imperfect Channel State Information and Directional Antenna: the Dilemma of Facilitating Reliability and Improving Security

The performance of hybrid satellite-terrestrial relaying (HSTR) networks is investigated in this work. Specifically, we examine the trade-off between reliability and security in HSTR networks using two key parameters: outage probability (OP) and intercept probability (IP). Both metrics are derived in closed-form expressions under the assumption of imperfect channel state information (CSI) for the legitimate channels. Additionally, a directional antenna is employed to compensate for the significant path loss caused by the long transmission distance between the satellite and the ground terminal. Numerical computations are provided to validate the accuracy of the derived framework. Furthermore, our findings reveal that increasing the satellite's transmit power and altitude has opposite effects on security and reliability. Specifically, increasing the transmit power enhances system reliability but reduces security. In contrast, a higher satellite altitude decreases reliability but improves security. These findings are further validated through Monte Carlo-based simulations.