Performance Analysis of DF Based mixed VLC-FSO-VLC System

In this paper the performance of decode-and-forward (DF) based mixed visible light communication-free space optical communication-visible light communication (VLC-FSO-VLC) co-operative system is presented. In the proposed system, the FSO link is used for providing the outdoor connectivity and VLC environment is used for indoor connectivity. The FSO link is characterized by the impact of Double Generalized Gamma (DGG) distributed atmospheric turbulence and Rayleigh distributed pointing errors and VLC environment follows the Lambertian radiation pattern of the light-emitting-diode (LED). For this system, novel mathematical expressions are derived for probability density function and cumulative distribution function of the system’s signal-to-noise-ratio (SNR). Using these SNR statistics, the closed-form analytical expressions of average bit-error rate (BER) for binary modulation techniques considering the possibility of perfect decoding by the DF relays are obtained. The results show that the BER of the considered VLC-FSOVLC system gives a better performance while using coherent binary phase shift keying (CBPSK) modulation technique as compared to other modulation techniques.