RIS-Assisted Multihop FSO/RF Hybrid System for Vehicular Communications over Generalized Fading

Abstract

Reconfigurable intelligent surface (RIS) is a promising technology to avoid signal blockage by creating line-ofsight (LOS) connectivity for free-space optical (FSO) and radio frequency (RF) wireless systems. There is limited research on the use of multiple RIS between a source and destination for wireless communications. This paper analyzes the performance of a RISassisted multi-hop transmission for vehicular communications by employing multiple RIS to enable LOS communication and reliable connectivity for a hybrid FSO and RF system. We develop an analytical framework to derive statistical results of the signalto-noise ratio (SNR) of a multi-RIS communication system over general fading models. We use decode-and-forward (DF) and fixed-gain (FG) relaying protocols to mix multi-RIS transmissions over RF and FSO technologies, and derive probability density and distribution functions for both the relaying schemes by considering independent and non-identical double generalized gamma (dGG) distribution models for vehicular RF transmissions and atmospheric turbulence for FSO system combined with zeroboresight pointing errors. We analyze the performance of a moving vehicle connected to one of the RIS modules by deriving exact analytical expressions of the outage probability, average bit-error rate (BER), and ergodic capacity in terms of Fox's H-function. We present asymptotic analysis and diversity order of the outage probability in the high SNR regime to provide a better insight into the system performance. We use computer simulations to demonstrate the effect of multiple RIS modules, fading parameters, and pointing errors on the RIS-aided multihop transmissions for the considered vehicular communication system.

RIS-Assisted Vehicular Network with Direct Transmission over Double-Generalized Gamma Fading Channels

“…In [19], the placement of multiple RIS is optimized for vehicleto-everything (V2X) communications. In [21], we analyzed the performance of multiple RIS-based vehicular communications over double Generalized-Gamma (dGG) fading model. In the aforementioned research, the direct signal received from the source is ignored.…”