Effect of Correlated Turbulence on Integrated SAG-FSO/SH-FSO/RF Transmission for Satellite Communications

Free-space optics (FSO) is slated as a promising solution to support extremely high data rates for future satellite communications (SatCom). Nonetheless, FSO transmission is susceptible to atmospheric turbulence impacts. Space-air-ground (SAG) FSO and hybrid single-hop (SH) FSO/radio frequency (RF) transmission systems are suggested to enhance the performance and reliability of FSO-based SatCom systems. They can also be integrated to further improve system performance. Previous work analyzed the performance of the resulting integrated SAG-FSO/SH-FSO/RF transmission system, assuming independent turbulence effects. In this paper, we perform a capacity analysis of the system in the presence of correlated turbulence. A novel analytical expression for the end-to-end ergodic capacity is derived and validated by Monte Carlo simulations. The numerical results demonstrate that, although the correlated turbulence adversely affects its performance, the integrated transmission system can still achieve a considerable capacity gain over existing solutions.