This paper proposes a rate adaptation design for high altitude platform
(HAP)-aided relaying satellite hybrid free-space optical/radio-frequency
(FSO/RF) systems. The design allows switching between two links
gradually to reduce the fre- quent link switching in error-prone
environments of conventional fixed-rate hybrid FSO/RF systems. System
performance metrics, including average transmission rate and outage
probability, are analytically studied under the presence of clouds and
fading of FSO and RF channels modeled respectively by Gamma-Gamma and
Rician distributions. The numerical results quantitatively highlight the
effectiveness of our proposed systems over the conventional ones.
Moreover, Monte-Carlo simulations are also performed to validate the
accuracy of the analytical model.