Feedback Error Tolerant Relay Antenna Selection Strategies for Secure Hybrid Satellite‐Terrestrial Networks

This paper investigates the secrecy performance of a dual‐hop hybrid satellite‐terrestrial relay network in the presence of a terrestrial eavesdropper. A decode‐and‐forward relay equipped with multiple antennas bridges a Shadowed‐Rician faded satellite link and a Nakagami‐ faded terrestrial link. To exploit spatial diversity, two feedback‐aided antenna‐selection schemes at the relay are proposed: Scheme I (best‐two relay antenna selection), selects the two antennas that maximize the end‐to‐end signal‐to‐noise ratio. Scheme II (cluster relay antenna selection) partitions the antenna array into clusters of two antennas and selects the antenna having the highest signal‐to‐noise ratio from each cluster. Closed‐form expressions for the secrecy outage probability is derived for both schemes by explicitly modeling feedback imperfections in the selection process, and their accuracy is validated through extensive Monte Carlo simulations. We then utilized the SOP expressions to derive effective secrecy throughput and intercept probability of the system. Moreover, an error‐tolerant weighting scheme is proposed for both schemes to optimize power allocation in the presence of feedback imperfections. A comparative analysis shows that Scheme I consistently outperforms Scheme II and conventional single‐antenna selection, even under erroneous feedback, while Scheme II remains advantageous in terms of reduced feedback overhead and lower selection complexity. The results also highlight the effects of key channel parameters (e.g., the Shadowed‐Rician and Nakagami fading severity) on the system secrecy.