Mixed RF/FSO Deep Space Communication System under Solar Scintillation Effect

The emerging technology of mixed radio frequency (RF)/free space optical (FSO) communications offers a great deal of merits in seamless channels and has potential for use in deep space exploration. In this article, a new paradigm with the dual-hop mixed RF/FSO system for the deep space communications link during a superior solar conjunction is proposed. The performance of this system, which is composed of an RF link between the Earth and a geosynchronous orbit relay satellite and an FSO link between the satellite and a deep space probe is evaluated for the first time to the best of our knowledge. An asymmetric environment is considered, where the RF link is subjected to Nakagami-m fading and the FSO link is assumed to follow an exponentiated Weibull distribution, which is induced by coronal turbulence. Under the assumption of amplify-and-forward relaying, we first derive the cumulative density function and the probability density function of this deep space mixed RF/FSO system. Thereafter, the closed-form expressions for the system performance-such as the end-to-end outage probability, the average bit error rate for the $M$-ary phase shift keying modulation scheme, and the channel ergodic capacity-are determined in terms of Meijer's G function. Numerical results are provided to validate our theoretical expressions. The results suggest that the performance of our proposed deep space mixed RF/FSO system is vulnerable to some key parameters, but it still outperforms its pure RF and FSO counterparts. Consequently, this study paves the way for constructing a future deep space communication network.