LEO Relay-Aided GEO Satellite-Terrestrial Transmissions

Though geostationary Earth orbit (GEO) satellites can provide seamless service for the terrestrial terminals across the globe, the transmission quality may not always be promised due to the associated long-distance path loss and the deep shadow fading arising from the obstacles around the terrestrial terminals. With a high probability of line-of-sight transmissions, low-Earth-orbit (LEO) satellites can be considered a promising way to bring diversity gain to improve the delivery quality over the direct GEO satellite-terrestrial transmission link. In this work, an LEO relay-aided GEO satellite-terrestrial system, including a GEO satellite transmitter (G), a randomly deployed terrestrial receiver (U), and a randomly distributed LEO satellite (L), is considered. Specifically, regarding the decode-and-forward relay scheme adopted at the LEO satellite and adopting geometric probability theory, we investigate the end-to-end outage performance of the G-L-U relay link. Moreover, we also derive the analytical expression for the outage performance of the direct G-U link. Then, the performance of the two links is compared to explore suitable angle ranges to exploit the benefit of introducing the LEO satellite relay. Finally, numerical results are presented to verify the correctness of the proposed analysis models.