Reconfigurable Intelligent Surfaces-Aided Mixed THz/FSO Communication System

In this paper, performance of a mixed terahertz/free space optics (THz/FSO) system is scrutinized under various environmental impediments, namely fog, pointing errors, atmospheric turbulence, and path-loss. Further, both the links are assisted by reconfigurable intelligent surfaces (RIS) and integrated using a decode-and-forward relay. The proposed system seeks to enhance the performance of the existing mixed THz/FSO system in terms of reliability. The exact expressions for the probability density function and cumulative distribution function are derived in the form of a Multivariable Fox's H-function. With the aid of statistical functions, average bit error rate and outage probability expressions for the mixed system are derived. Additionally, numerical outcomes are showcased in order to quantify the performance of the proposed system. A comparison between mixed THz/FSO systems with and without RIS reveals that the mixed THz/FSO system with RIS outperforms the mixed system without RIS. Lastly, analytical expressions are authenticated with the help of Monte-Carlo simulations.