Security-Reliability TradeOff Analysis of Hybrid Satellite-Terrestrial Uplink Communications With Relay Selection

In this article, we study a hybrid satellite-terrestrial uplink system (HSTUS), where a terrestrial source transmits its messages to a geostationary Earth orbit satellite aided by multiple relays in the presence of co-channel interference (CCI) and an eavesdropper. To enhance the security-reliability tradeoff (SRT) performance of the HSTUS, we propose two relay selection schemes by considering the usability of channel state information (CSI) of CCI channels, namely, the relay selection with partial CSI (RSwPCSI) where the CCI links' CSI is unknown, and the relay selection with full CSI (RSwFCSI) where the CCI links' CSI is available. We employ the conventional round-robin scheduling (CRRS) scheme for performance comparison purposes. Then, we analyze both exact and asymptotic SRT performance of the CRRS, RSwPCSI, and RSwFCSI schemes by investigating their outage and intercept probabilities in CCI environments. Simulation results show that the proposed RSwPCSI and RSwFCSI schemes have better SRT performance than the CRRS scheme. Increasing the number of relays obviously improves SRT performance of the proposed RSwPCSI and RSwFCSI schemes while that of the CRRS remains unchanged, which indicates the advantages of employing the proposed RSwPCSI and RSwFCSI schemes. Moreover, the optimal SRT performance can be obtained for the three schemes by using the optimal signal-to-noise errors, which are calculated by the golden search-based iterative method.